Capsaicin is the active component of
chili pepperChili pepper is the fruit of plants from the genus Capsicum, members of the nightshade family, Solanaceae. The term in British English and in Australia, New Zealand, India, Malaysia and other Asian countries is just chilli without pepper.Chili peppers originated in the Americas...
s, which are plants belonging to the
genusIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
CapsicumCapsicum is a genus of flowering plants in the nightshade family, Solanaceae. Its species are native to the Americas where they have been cultivated for thousands of years, but they are now also cultivated worldwide, used as spices, vegetables, and medicines - and have become are a key element in...
. It is an
irritantIrritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
for
mammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, including
humanHumans are the only living species in the Homo genus...
s, and produces a sensation of burning in any
tissueTissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
with which it comes into contact. Capsaicin and several related compounds are called
capsaicinoids and are produced as a
secondary metaboliteSecondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...
by chili peppers, probably as deterrents against certain
herbivoreHerbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s and fungi. Pure capsaicin is a hydrophobic, colorless, odorless, highly spicy crystalline to waxy compound.
History
The compound was first extracted (albeit in impure form) in 1816 by Christian Friedrich Bucholz (1770–1818). He called it "capsicin," after the genus
CapsicumCapsicum is a genus of flowering plants in the nightshade family, Solanaceae. Its species are native to the Americas where they have been cultivated for thousands of years, but they are now also cultivated worldwide, used as spices, vegetables, and medicines - and have become are a key element in...
from which it was extracted. John Clough Thresh (1850–1932), who had isolated capsaicin in almost pure form, gave it the name "capsaicin" in 1876. But it was Karl Micko who first isolated capsaicin in pure form in 1898. Capsaicin's empirical formula (chemical composition) was first determined by E. K. Nelson in 1919; he also partially elucidated capsaicin's chemical structure. Capsaicin was first synthesized in 1930 by E. Spath and S. F. Darling. In 1961, similar substances were isolated from
chili pepperChili pepper is the fruit of plants from the genus Capsicum, members of the nightshade family, Solanaceae. The term in British English and in Australia, New Zealand, India, Malaysia and other Asian countries is just chilli without pepper.Chili peppers originated in the Americas...
s by the Japanese chemists S. Kosuge and Y. Inagaki, who named them capsaicinoids.
In 1873 German pharmacologist
Rudolf BuchheimRudolf Buchheim was a German pharmacologist who was born in Bautzen. In 1845 he earned his doctorate from the University of Leipzig and soon after became a professor at the University of Dorpat. While at Dorpat he created the first pharmacological institute at that school...
(1820–1879) and in 1878 the Hungarian doctor Endre Hőgyes stated that "capsicol" (partially purified capsaicin) caused the burning feeling when in contact with
mucous membraneThe mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...
s and increased secretion of gastric juice.
Capsaicinoids
Capsaicin is the main capsaicinoid in chili peppers, followed by
dihydrocapsaicinDihydrocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers . Like capsaicin it is an irritant. Dihydrocapsaicin accounts for about 22% of the total capsaicinoids mixture and has about the same pungency as capsaicin. Pure dihydrocapsaicin is a lipophilic colorless...
. These two compounds are also about twice as potent to the taste and nerves as the minor capsaicinoids
nordihydrocapsaicinNordihydrocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers .- Properties :Like capsaicin, it is an irritant. Nordihydrocapsaicin accounts for about 7% of the total capsaicinoids mixture and has about half the pungency of capsaicin. Pure nordihydrocapsaicin is a...
,
homodihydrocapsaicinHomodihydrocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers . Like capsaicin it is an irritant. Homodihydrocapsaicin accounts for about 1% of the total capsaicinoids mixture and has about half the pungency of capsaicin. Pure homodihydrocapsaicin is a lipophilic...
, and
homocapsaicinHomocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers . Like capsaicin it is an irritant. Homocapsaicin accounts for about 1% of the total capsaicinoids mixture and has about half the pungency of capsaicin. Pure homocapsaicin is a lipophilic colorless odorless...
. Dilute solutions of pure capsaicinoids produced different types of pungency; however, these differences were not noted using more concentrated solutions.
Capsaicin is believed to be synthesized in the interlocular septa of chili peppers by addition of a branched-chain
fatty acidIn chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
to
vanillylIn organic chemistry, vanillyl is a functional group. Compounds containing a vanillyl group are called vanilloids, and include vanillin, vanillic acid, capsaicin and VMA....
amine; specifically, capsaicin is made from vanillylamine and 8-methyl-6-nonenoyl CoA (where CoA =
Coenzyme ACoenzyme A is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All sequenced genomes encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it as a substrate...
). Biosynthesis depends on the gene
AT3, which resides at the
pun1 locusIn the fields of genetics and genetic computation, a locus is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map...
, and which encodes a putative
acyltransferaseAcyltransferase is a type of transferase enzyme that acts upon acyl groups.Examples include:* Glyceronephosphate O-acyltransferase* Lecithin-cholesterol acyltransferase...
.
Besides the six natural capsaicinoids, one synthetic member of the capsaicinoid family exists.
Vanillylamide of n-nonanoic acidNonivamide, also called pelargonic acid vanillylamide or PAVA, is an organic compound and a capsaicinoid. It is an amide of pelargonic acid and vanillyl amine. It is present in chili peppers, but is commonly manufactured synthetically...
(VNA, also PAVA) is used as a reference substance for determining the relative pungency of capsaicinoids.
| Capsaicinoid name |
Abbrev. |
Typical
relative
amount |
Scoville The Scoville scale is a measurement of the spicy heat of a chili pepper. The number of Scoville heat units indicates the amount of capsaicin present. Capsaicin is a chemical compound that stimulates chemoreceptor nerve endings in the skin, especially the mucous membranes.The scale is named after...
heat units |
Chemical structure |
| Capsaicin |
C |
69% |
16,000,000 |
|
DihydrocapsaicinDihydrocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers . Like capsaicin it is an irritant. Dihydrocapsaicin accounts for about 22% of the total capsaicinoids mixture and has about the same pungency as capsaicin. Pure dihydrocapsaicin is a lipophilic colorless...
|
DHC |
22% |
15,000,000 |
|
NordihydrocapsaicinNordihydrocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers .- Properties :Like capsaicin, it is an irritant. Nordihydrocapsaicin accounts for about 7% of the total capsaicinoids mixture and has about half the pungency of capsaicin. Pure nordihydrocapsaicin is a...
|
NDHC |
7% |
9,100,000 |
|
HomodihydrocapsaicinHomodihydrocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers . Like capsaicin it is an irritant. Homodihydrocapsaicin accounts for about 1% of the total capsaicinoids mixture and has about half the pungency of capsaicin. Pure homodihydrocapsaicin is a lipophilic...
|
HDHC |
1% |
8,600,000 |
|
HomocapsaicinHomocapsaicin is a capsaicinoid and analog and congener of capsaicin in chili peppers . Like capsaicin it is an irritant. Homocapsaicin accounts for about 1% of the total capsaicinoids mixture and has about half the pungency of capsaicin. Pure homocapsaicin is a lipophilic colorless odorless...
|
HC |
1% |
8,600,000 |
|
NonivamideNonivamide, also called pelargonic acid vanillylamide or PAVA, is an organic compound and a capsaicinoid. It is an amide of pelargonic acid and vanillyl amine. It is present in chili peppers, but is commonly manufactured synthetically...
|
PAVA |
|
|
|
Natural function
Capsaicin is present in large quantities in the placental tissue (which holds the seeds), the internal membranes and, to a lesser extent, the other fleshy parts of the
fruitIn broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s of plants in the genus
CapsicumCapsicum is a genus of flowering plants in the nightshade family, Solanaceae. Its species are native to the Americas where they have been cultivated for thousands of years, but they are now also cultivated worldwide, used as spices, vegetables, and medicines - and have become are a key element in...
. The seeds themselves do not produce any capsaicin, although the highest concentration of capsaicin can be found in the white pith of the inner wall, where the seeds are attached.
The seeds of
Capsicum plants are predominantly dispersed by
birdBirds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s. The TRPV1 channel to which capsaicin binds does not respond to capsaicin and related chemicals in birds (avian vs mammalian TRPV1 show functional diversity and selective sensitivity). Chili pepper seeds consumed by birds pass through the digestive tract and can germinate later, but mammals have
molar teethMolars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
, which destroy seeds and prevent them from germinating. Thus, natural selection may have led to increasing capsaicin production because it makes the plant less likely to be eaten by animals that do not help it reproduce. There is also evidence that capsaicin evolved as an anti-fungal agent, and capsaicinoids are broadly anti-microbial.
In 2006, it was discovered that
tarantulaTarantulas comprise a group of often hairy and often very large arachnids belonging to the family Theraphosidae, of which approximately 900 species have been identified. Some members of the same Suborder may also be called "tarantulas" in the common parlance. This article will restrict itself to...
venomVenom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
activates the same pathway of pain as is activated by capsaicin, the first demonstrated case of such a shared pathway in both plant and animal anti-mammal defense.
Food
Because of the burning sensation caused by capsaicin when it comes in contact with mucous membranes, it is commonly used in food products to give them added spice or "heat" (pungency). In high concentrations capsaicin will also cause a burning effect on other sensitive areas of skin. The degree of heat found within a food is often measured on the
Scoville scaleThe Scoville scale is a measurement of the spicy heat of a chili pepper. The number of Scoville heat units indicates the amount of capsaicin present. Capsaicin is a chemical compound that stimulates chemoreceptor nerve endings in the skin, especially the mucous membranes.The scale is named after...
. In some cases people enjoy the pain; there has long been a demand for capsaicin spiced food and beverages. There are many cuisines and food products featuring capsaicin such as hot sauce, salsa, and beverages. For information on treatment see the section Treatment after exposure.
Beverage
Recently beverage products are emerging with capsaicin as an active ingredient. The first two capsaicin beverages to hit the market are Prometheus Springs Elixirs launched in 2007 and Sweet16 launched in 2011. It is common for people to experience pleasurable and even euphoriant effects from ingesting capsaicin.
FolkloreFolklore consists of legends, music, oral history, proverbs, jokes, popular beliefs, fairy tales and customs that are the traditions of a culture, subculture, or group. It is also the set of practices through which those expressive genres are shared. The study of folklore is sometimes called...
among self-described "chiliheads" attributes this to pain-stimulated release of endorphins, a different mechanism from the local receptor overload that makes capsaicin effective as a topical analgesic. In support of this theory, there is some evidence that the effect can be blocked by
naloxoneNaloxone is an opioid antagonist drug developed by Sankyo in the 1960s. Naloxone is a drug used to counter the effects of opiate overdose, for example heroin or morphine overdose. Naloxone is specifically used to counteract life-threatening depression of the central nervous system and respiratory...
and other compounds that compete for receptor sites with endorphins and opiates.
Medical
Capsaicin is currently used in topical ointments, as well as a high-dose
dermal patchA dermal patch or skin patch is a medicated adhesive patch that is placed on the skin to deliver a medication into the skin. This is in contrast to a transdermal patch, which delivers the medication through the skin and into the bloodstream....
(trade name
Qutenza), to relieve the
painPain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
of peripheral neuropathy such as post-herpetic
neuralgiaNeuralgia is pain in one or more nerves that occurs without stimulation of pain receptor cells. Neuralgia pain is produced by a change in neurological structure or function rather than by the excitation of pain receptors that causes nociceptive pain. Neuralgia falls into two categories: central...
caused by shingles. It may be used in concentrations of between 0.025% and 0.075%. It may be used as a cream for the temporary relief of minor aches and pains of
muscleMuscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s and joints associated with
arthritisArthritis is a form of joint disorder that involves inflammation of one or more joints....
, simple backache, strains and
sprainA sprain is an injury in a joint, caused by the ligament being stretched beyond its capacity. A muscular tear caused in the same manner is referred to as a strain. In cases where either ligament or muscle tissue is torn, immobilization and surgical repair may be necessary...
s, often in compounds with other rubefacients. The treatment typically involves the application of a topical anesthetic until the area is numb. Then the capsaicin is applied by a therapist wearing
rubber gloveA rubber glove is a glove made out of rubber. Rubber gloves can be unsupported or supported . Its primary purpose is protection of the hands while performing tasks involving chemicals. Rubber gloves are worn during dishwashing to protect the hands from detergent and allow the use of hotter water...
s and a face mask. The capsaicin remains on the skin until the patient starts to feel the "heat", at which point it is promptly removed. Capsaicin is also available in large
bandageCapsicum Plaster is a type of plaster that is applied to relieve pain and reduce counteritching in patients. It is very common in Chinese medicine, like acupuncture.- Sources :...
s that can be applied to the back.
Capsaicin creams are used to treat
psoriasisPsoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
as an effective way to reduce itching and inflammation.
According to animal and human studies, the oral intake of capsaicin may increase the production of heat by the body for a short time. Due to the effect on the carbohydrates breakdown after a meal, cayenne may also be used to regulate blood sugar levels. Further research is required to see if capsaicin would be useful to treat obesity.
Substance PIn the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
, a
neuropeptideNeuropeptides are small protein-like molecules used by neurons to communicate with each other. They are neuronal signaling molecules, influence the activity of the brain in specific ways and are thus involved in particular brain functions, like analgesia, reward, food intake, learning and...
released by capsaicin, has been shown to reverse diabetes in mice, but the effects to insulin secretion seems to be species dependent. In humans, substance P seems to decrease insulin release and cause fluctuations in blood sugar levels.
In 1997, a research team led by David Julius of
UCSFThe University of California, San Francisco is one of the world's leading centers of health sciences research, patient care, and education. UCSF's medical, pharmacy, dentistry, nursing, and graduate schools are among the top health science professional schools in the world...
showed that capsaicin selectively binds to a protein known as
TRPV1The transient receptor potential cation channel subfamily V member 1 ', also known as the capsaicin receptor and the vanilloid receptor 1, is a protein that, in humans, is encoded by the TRPV1 gene...
that resides on the membranes of pain and heat sensing neurons. TRPV1 is a heat activated calcium channel, which opens between 37 and 45 °C (98.6 and 113 °F, respectively). When capsaicin binds to TRPV1, it causes the channel to open below 37 °C (
normal human body temperatureNormal human body temperature, also known as normothermia or euthermia, is a concept that depends upon the place in the body at which the measurement is made, and the time of day and level of activity of the person...
), which is why capsaicin is linked to the sensation of heat. Prolonged activation of these neurons by capsaicin depletes presynaptic
substance PIn the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
, one of the body's neurotransmitters for pain and heat. Neurons that do not contain TRPV1 are unaffected.
The result appears to be that the chemical mimics a burning sensation, the
nerveA peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s are overwhelmed by the influx, and are unable to report pain for an extended period of time. With chronic exposure to capsaicin,
neuronA neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s are depleted of neurotransmitters, leading to reduction in sensation of pain and blockade of
neurogenic inflammationNeurogenic inflammation is inflammation arising from the local release from afferent neurons of inflammatory mediators such as Substance P and Calcitonin Gene-Related Peptide ....
. If capsaicin is removed, the neurons recover.
Capsaicin is being explored as a possible prophylaxis for Type 1 diabetes by researchers in Toronto, Canada. Capsaicin was injected subcutaneously in neonatal diabetes-prone NOD mice to permanently remove a prominent subset of pancreatic sensory neurons, which express the transient receptor potential vanilloid-1 (TRPV1) protein. Insulin resistance and beta cell stress of prediabetic NOD mice are prevented when TRPV1+ neurons are eliminated. In other words, mice who were genetically predisposed to Type 1 diabetes were prevented from developing Type 1 via removal of these neurons, which are thought to attract pathogenic T-cells to attacking pancreatic beta cells (i.e., the cause of Type 1 diabetes).
The
American Association for Cancer ResearchThe American Association for Cancer Research is the world's oldest and largest professional association to advancing cancer research. Based in Philadelphia, AACR focuses on all aspects of cancer research including basic, clinical and translational research into the etiology, prevention, diagnosis,...
reports studies suggesting capsaicin is able to kill
prostate cancerProstate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...
cells by causing them to undergo
apoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
. The studies were performed on tumors formed by human prostate cancer cell cultures grown in mouse models, and showed tumors treated with capsaicin were about one-fifth the size of the untreated tumors. There have been several clinical studies conducted in Japan and China that showed natural capsaicin directly inhibits the growth of leukemic cells.
Another study carried out at the
University of NottinghamThe University of Nottingham is a public research university based in Nottingham, United Kingdom, with further campuses in Ningbo, China and Kuala Lumpur, Malaysia...
suggests capsaicin is able to trigger
apoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
in human
lung cancerLung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
cells as well.
Capsaicin is also the key ingredient in the experimental drug Adlea, which is in Phase 2 trials as a long-acting analgesic to treat post-surgical and osteoarthritis pain for weeks to months after a single injection to the site of pain. More over, it reduces pain resulted
rheumatoid arthritisRheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...
as well as joint or muscle pain from
fibromyalgiaFibromyalgia is a medical disorder characterized by chronic widespread pain and allodynia, a heightened and painful response to pressure. It is an example of a diagnosis of exclusion...
or other causes.
Proposed drug abuse deterrent
Clifford Woolf, the Richard J. Kitz Professor of Anesthesia Research at
Harvard Medical SchoolHarvard Medical School is the graduate medical school of Harvard University. It is located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts....
, has suggested using capsaicin to deter abuse of certain extended-release drugs such as OxyContin and Ritalin. When taken as prescribed, opioid prescription drugs such as OxyContin or stimulant drugs such as Adderall XR release their active chemical over time, but when crushed and insufflated, taken as a suppository, chewed, or injected, the larger than normal dosage is absorbed all at once and a much stronger effect is produced that can be highly habit forming and potentially fatal due to the higher risk of overdose. Woolf has argued that adding capsaicin into the capsules would be a safe way to deter abuse. A person taking the capsule in the prescribed way (
i.e., swallowing it whole) would suffer no ill effects from the additive. However, a person crushing it would expose the irritant. Anyone then chewing it, snorting it, or injecting it would be exposed to the full power of the chemical. "Imagine snorting an extract of 50 jalapeño peppers and you get the idea," Woolf said in an interview with the Harvard University Gazette. As of 2006, Woolf's proposal is still in the preliminary stages of development and the additive has not yet entered the production stage. A major downside of the idea is that drug users would likely turn to polluted street drugs rather than abusing pure pills. Also, should a user choose to crush a number of pills and swallow them inside a medium, such as rolling paper or tissue, the danger of ill effects or overdose may exist not only from the drug itself, but also as a result of the large dose of capsaicin the individual would be exposed to over a short period of time.
Less-than-lethal force
Capsaicin is also the active ingredient in riot control and personal defense
pepper sprayPepper spray, also known as OC spray , OC gas, and capsicum spray, is a lachrymatory agent that is used in riot control, crowd control and personal self-defense, including defense against dogs and bears...
chemical agents. When the spray comes in contact with
skinThe human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals,...
, especially
eyeThe human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
s or
mucous membraneThe mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...
s, it is very painful, and breathing small particles of it as it disperses can cause breathing difficulty, which serves to discourage assailants. Refer to the
Scoville scaleThe Scoville scale is a measurement of the spicy heat of a chili pepper. The number of Scoville heat units indicates the amount of capsaicin present. Capsaicin is a chemical compound that stimulates chemoreceptor nerve endings in the skin, especially the mucous membranes.The scale is named after...
for a comparison of pepper spray to other sources of capsaicin.
In large quantities, capsaicin can cause
deathDeath is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
. Symptoms of overdose include difficulty breathing, blue skin, and convulsions. The large amount needed to kill an adult human and the low concentration of capsaicin in chilies make the risk of accidental poisoning by chili consumption negligible.
Pest deterrent
Capsaicin is also used to deter mammalian pests. A common example is the use of ground-up or crushed dried chili pods in birdseed to deter squirrels, since birds are unaffected by capsaicin. Another example is the use of chili peppers by the
Elephant Pepper Development TrustThe Elephant Pepper Development Trust is a non-profit educational organization aimed at resolving human-wildlife conflict in rural areas of Africa...
to improve crop security for rural communities in Africa.
Although hot chili pepper extract is commonly used as a component of household and garden insect repellent formulas, it is not clear that the capsaicinoid elements of the extract are responsible for its repellency.
There are manufacturers that do sell a capsaicin-based gel product that is reported to be a
feral-pigeonFeral pigeons , also called city doves, flying rats, city pigeons or street pigeons, are derived from domestic pigeons that have returned to the wild. The domestic pigeon was originally bred from the wild Rock Pigeon, which naturally inhabits sea-cliffs and mountains. All three types readily...
(
Columba livia) deterrent from specific roosting and loafing areas. Some of these products do have an EPA label and NSF approval.
Equestrian sports
Capsaicin is a banned substance in
equestrian sportsEquestrianism more often known as riding, horseback riding or horse riding refers to the skill of riding, driving, or vaulting with horses...
because of its hypersensitizing and pain relieving properties. At the show jumping events of the
2008 Summer OlympicsThe 2008 Summer Olympics, officially known as the Games of the XXIX Olympiad, was a major international multi-sport event that took place in Beijing, China, from August 8 to August 24, 2008. A total of 11,028 athletes from 204 National Olympic Committees competed in 28 sports and 302 events...
, four horses tested positive for the substance, which resulted in disqualification.
Mechanism of action
The burning and painful sensations associated with capsaicin result from its chemical interaction with sensory
neuronA neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s. Capsaicin, as a member of the vanilloid family, binds to a receptor called the vanilloid receptor subtype 1 (VR1). First cloned in 1997, VR1 is an
ion channelIon channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
-type receptor. VR1, which can also be stimulated with heat and physical abrasion, permits cations to pass through the
cell membraneThe cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
and into the cell when activated. The resulting
depolarizationIn biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential...
of the neuron stimulates it to
signalIn physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
the brain. By binding to the VR1 receptor, the capsaicin molecule produces the same sensation that excessive heat or abrasive damage would cause, explaining why the spiciness of capsaicin is described as a burning sensation.
The VR1
ion channelIon channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
has subsequently been shown to be a member of the superfamily of
TRPTransient receptor potential channels are a group of ion channels located mostly on the plasma membrane of numerous human and animal cell types. There are about 28 TRP channels that share some structural similarity to each other...
ion channels, and as such is now referred to as . There are a number of different
TRPTransient receptor potential channels are a group of ion channels located mostly on the plasma membrane of numerous human and animal cell types. There are about 28 TRP channels that share some structural similarity to each other...
ion channels that have been shown to be sensitive to different ranges of temperature and probably are responsible for our range of temperature sensation. Thus, capsaicin does not actually cause a
chemical burnA chemical burn occurs when living tissue is exposed to a corrosive substance such as a strong acid or base. Chemical burns follow standard burn classification and may cause extensive tissue damage. The main types of irritant and/or corrosive products are: acids, bases, oxidizers, solvents,...
, or indeed any direct tissue damage at all, when chili peppers are the source of exposure. The inflammation resulting from exposure to Capsaicin is believed to be the result of the body's reaction to nerve excitement. For example, the mode of action of capsaicin in inducing bronchoconstriction is thought to involve stimulation of C fibres culminating in the release of neuropeptides. Basically, the body inflames tissues as if it has undergone a burn or abrasion and the resulting inflamation can cause tissue damage in cases of extreme exposure, as is the case for many substances that trick the body into inflaming itself.
Acute health effects
Capsaicin is a highly irritant material requiring proper protective goggles, respirators, and proper hazardous material handling procedures. Capsaicin takes effect upon skin contact (irritant, sensitizer), eye contact (irritant), ingestion, and inhalation (lung irritant, lung sensitizer). Severe over-exposure to pure capsaicin can result in death; the lethal dose ( in mice) is 47.2 mg/kg.
Painful exposures to capsaicin-containing peppers are among the most common plant-related exposures presented to poison centers. They cause burning or stinging pain to the skin, and if ingested in large amounts by adults or small amounts by children, can produce nausea, vomiting, abdominal pain and burning diarrhea. Eye exposure produces intense tearing, pain,
conjunctivitisConjunctivitis refers to inflammation of the conjunctiva...
and
blepharospasmA blepharospasm , is any abnormal contraction or twitch of the eyelid....
.
Drug interactions
Capsaicin is indicated as interacting with a number of drugs, including the commonly prescribed high-blood pressure drug
LisinoprilLisinopril is a drug of the angiotensin-converting enzyme inhibitor class that is primarily used in treatment of hypertension, congestive heart failure, and heart attacks and also in preventing renal and retinal complications of diabetes. Its indications, contraindications and side effects are as...
, to induce a side-effect cough.
Treatment after exposure
The primary treatment is removal from exposure. Contaminated clothing should be removed and placed in airtight bags to prevent secondary exposure.
For external exposure, bathing the mucous membrane surfaces that have contacted capsaicin with oily compounds such as vegetable oil, paraffin oil,
petroleum jellyPetroleum jelly, petrolatum, white petrolatum or soft paraffin, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons , originally promoted as a topical ointment for its healing properties...
(
VaselineVaseline is a brand of petroleum jelly based products owned by Anglo-Dutch company Unilever. Products include plain petroleum jelly and a selection of skin creams, soaps, lotions, cleansers, deodorants and personal lubricants....
),
creamsA cream is a topical preparation usually for application to the skin. Creams for application to mucus membranes such as those of the rectum or vagina are also used. Creams may be considered pharmaceutical products as even cosmetic creams are based on techniques developed by pharmacy and...
, or
polyethylene glycolPolyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...
is the most effective way to attenuate the associated discomfort; since oil and capsaicin are both hydrophobic hydrocarbons the capsaicin which has not already been absorbed into tissues will be picked up into solution and easily removed. Capsaicin can also be washed off the skin using
soapIn chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
,
shampooShampoo is a hair care product used for the removal of oils, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair...
, or other
detergentA detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
s. Plain water is
ineffective at removing capsaicin, as are
vinegarVinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...
,
bleachBleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...
,
sodium metabisulfiteSodium metabisulfite or sodium pyrosulfite is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium...
, topical
antacidAn antacid is a substance which neutralizes stomach acidity.-Mechanism of action:Antacids perform a neutralization reaction, increasing the pH to reduce acidity in the stomach. When gastric hydrochloric acid reaches the nerves in the gastrointestinal mucosa, they signal pain to the central nervous...
suspensions, and other
home remediesA home remedy is a treatment to cure a disease or ailment that employs certain spices, vegetables, or other common items. Home remedies may or may not have medicinal properties that treat or cure the disease or ailment in question, as they are typically passed along by laypersons...
.
Additionally when ingested, cold
milkMilk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...
is an effective way to treat the burning sensation (due to
caseinCasein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....
s having a
detergentA detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
effect on capsaicin); and room temperature sugar solution (10%) at 20 °C (68 °F) is almost as effective. The burning sensation will slowly fade away over several hours if no actions are taken.
Burning and pain symptoms can also be relieved by cooling, such as from ice, cold water, cold bottles, cold surfaces, or a flow of air from wind or a fan. In severe cases, eye burn might be treated symptomatically with topical ophthalmic anesthetics; mucous membrane burn with
lidocaineLidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...
gel. The gel from the aloe plant has also been shown to be very effective. Capsaicin-induced
asthmaAsthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
might be treated with nebulized
bronchodilatorA bronchodilator is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lungs. Bronchodilators may be endogenous , or they may be medications administered for the treatment of breathing difficulties...
s or oral
antihistamineAn H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...
s or
corticosteroidCorticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s.
Effects of dietary consumption
Ingestion of spicy food or ground jalapeño peppers does not cause mucosal erosions or other abnormalities. Some mucosal microbleeding has been found after eating red and black peppers, but there was no significant difference between
aspirinAspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
(used as a
controlScientific control allows for comparisons of concepts. It is a part of the scientific method. Scientific control is often used in discussion of natural experiments. For instance, during drug testing, scientists will try to control two groups to keep them as identical and normal as possible, then...
) and peppers. The question of whether chili ingestion increases or decreases risk of stomach cancer is unresolved: a study of Mexican patients found self-reported capsaicin intake levels associated with increased stomach cancer rates (however, this is very likely attributed to
Helicobacter pyloriHelicobacter pylori , previously named Campylobacter pyloridis, is a Gram-negative, microaerophilic bacterium found in the stomach. It was identified in 1982 by Barry Marshall and Robin Warren, who found that it was present in patients with chronic gastritis and gastric ulcers, conditions that were...
) while a study of Italians suggests eating hot peppers regularly was protective against stomach cancer. A preliminary study using county population and mortality data showed significantly higher rates for stomach and liver cancer in counties inhabited by groups with high consumption of capsaicin-rich foods than in matched control counties. Carcinogenic, co-carcinogenic, and anticarcinogenic effects of capsaicin have been reported in animal studies.
See also
- TRPV1
The transient receptor potential cation channel subfamily V member 1 ', also known as the capsaicin receptor and the vanilloid receptor 1, is a protein that, in humans, is encoded by the TRPV1 gene...
, the only known receptor (a transient receptor potentialTransient receptor potential channels are a group of ion channels located mostly on the plasma membrane of numerous human and animal cell types. There are about 28 TRP channels that share some structural similarity to each other...
channel) for capsaicin
- Scoville scale
The Scoville scale is a measurement of the spicy heat of a chili pepper. The number of Scoville heat units indicates the amount of capsaicin present. Capsaicin is a chemical compound that stimulates chemoreceptor nerve endings in the skin, especially the mucous membranes.The scale is named after...
, a measurement of the spicy heat (or piquance) of a chili pepper
- Capsazepine
Capsazepine is a synthetic analogue of capsaicin.-Pharmacaology:Capsazepine blocks the painful sensation of heat caused by capsaicin which activates the TRPV1 ion channel. It is therefore considered to be a capsaicin antagonist. The TRPV1 channel functions as a pain and temperature sensor in...
, capsaicin antagonist
- Piperine
Piperine is the alkaloid responsible for the pungency of black pepper and long pepper, along with chavicine . It has also been used in some forms of traditional medicine and as an insecticide. Piperine forms monoclinic needles, is slightly soluble in water and more so in alcohol, ether or...
, the active piquant chemical in black pepperBlack pepper is a flowering vine in the family Piperaceae, cultivated for its fruit, which is usually dried and used as a spice and seasoning. The fruit, known as a peppercorn when dried, is approximately in diameter, dark red when fully mature, and, like all drupes, contains a single seed...
- Allyl isothiocyanate
Allyl isothiocyanate is the organosulfur compound with the formula CH2CHCH2NCS. This colorless oil is responsible for the pungent taste of mustard, horseradish, and wasabi. This pungency and the lachrymatory effect of AITC is mediated through the TRPA1 and TRPV1 ion channels...
, the active piquant chemical in mustardMustards are several plant species in the genera Brassica and Sinapis whose small mustard seeds are used as a spice and, by grinding and mixing them with water, vinegar or other liquids, are turned into the condiment known as mustard or prepared mustard...
, radishThe radish is an edible root vegetable of the Brassicaceae family that was domesticated in Europe, in pre-Roman times. They are grown and consumed throughout the world. Radishes have numerous varieties, varying in size, color and duration of required cultivation time...
es, horseradishHorseradish is a perennial plant of the Brassicaceae family, which also includes mustard, wasabi, broccoli, and cabbages. The plant is probably native to south eastern Europe and the Arab World , but is popular around the world today...
, and wasabi, also known as Japanese horseradish, is a member of the Brassicaceae family, which includes cabbages, horseradish, and mustard. Its root is used as a condiment and has an extremely strong flavor. Its hotness is more akin to that of a hot mustard rather than the capsaicin in a chili pepper,...
- Allicin, the active piquant flavor chemical in uncooked garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...
and onions (see those articles for discussion of other chemicals in them relating to pungency, and eye irritation)
- Naga Viper pepper, Bhut Jolokia Pepper, BT Trinidad Scorpion Pepper
Trinidad Scorpion Butch T pepper is a chili pepper that has been measured as the world's hottest. The pepper is a particular strain of the Trinidad Scorpion . It is named after Butch Taylor, the owner of a hot sauce company who is responsible for propagating the pepper's seeds...
some of the world's most capsaicin-rich fruits
- Discovery and development of TRPV1 antagonists
Chronic pain remains a recognized unmet medical need. Consequently, the search for new analgesic agents is being intensively studied by the pharmaceutical industry. The TRPV1 receptor is an ion channel that has been implicated in mediation of many types of pain and therefore studied most extensively...
- Capsinoids
Capsinoids, which include capsiate, dihydrocapsiate, and nordihydrocapsiate, are substances naturally present in chili peppers. Although they are structurally similar to capsaicin, the substance that causes pungency in hot peppers, they largely lack that characteristic. Capsinoids have an...
, similar in structure to capsaicin, but lack the extreme pungency, and density
General references
- Garnanez RJ, McKee LH (2001) "Temporal effectiveness of sugar solutions on mouth burn by capsaicin" IFT Annual Meeting 2001
- Tarantula Venom, Chili Peppers Have Same "Bite," Study Finds http://news.nationalgeographic.com/news/2006/11/061108-tarantula-venom.html
- Minna M. Hamalainen, Alberto Subieta, Christopher Arpey, Timothy J. Brennan, "Differential Effect of Capsaicin Treatment on Pain-Related Behaviors After Plantar Incision," The Journal of Pain, 10,6 (2009), 637-645.
External links