2,4-Dinitrophenol
Encyclopedia
2,4-Dinitrophenol C6H4N2O5, is a cellular
metabolic
poison. It uncouples
oxidative phosphorylation
by carrying protons across the mitochondrial membrane, leading to a rapid consumption of energy
without generation of ATP
.
Dinitrophenols as a class of compounds, of which there are six members, do not occur naturally but are all manufactured compounds.
, acetone
, chloroform
, pyridine
, carbon tetrachloride
, toluene
, alcohol
, benzene
, and aqueous alkaline solutions. Its crystalline sodium salts are also soluble in water. It forms explosive salts with alkalies and ammonia
, and emits toxic fumes of nitrogen oxides when heated to decomposition. It is incompatible with heavy metals and their compounds.
s, other organic chemicals, and wood preservatives. It has also been used to make photographic developer, explosives, and pesticides.
, an agent that can shuttle protons (hydrogen ions) across biological membranes. It defeats the proton gradient across mitochondria and chloroplast
membranes, collapsing the proton motive force that the cell uses to produce most of its ATP
chemical energy. Instead of producing ATP, the energy of the proton gradient is lost as heat
.
DNP is often used in biochemistry
research
to help explore the bioenergetics
of chemiosmotic
and other membrane transport
processes.
, allowing protons to leak across the inner mitochondrial membrane and thus bypass ATP synthase
. This makes ATP energy production less efficient. In effect, part of the energy that is normally produced from cellular respiration is wasted as heat. The inefficiency is proportional to the dose of DNP that's taken. As the dose increases and energy production is made more inefficient, metabolic rate increases (and more fat is burned) in order to compensate for the inefficiency and meet energy demands. DNP is probably the best known agent for uncoupling oxidative phosphorylation
. The production or "phosphorylation
" of ATP by ATP synthase gets disconnected or "uncoupled" from oxidation. Interestingly, the factor that limits ever-increasing doses of DNP is not a lack of ATP energy production, but rather an excessive rise in body temperature due to the heat produced during uncoupling. Accordingly, DNP overdose will cause fatal hyperthermia
. In light of this, it's advised that the dose be slowly titrated according to personal tolerance, which varies greatly. Case reports have shown that an acute administration of 20–50 mg/kg in humans can be lethal. Concerns about dangerous side-effects and rapidly developing cataracts resulted in DNP being discontinued in the United States by the end of 1938. DNP, however, continues to be used by some bodybuilders
and athletes to rapidly lose body fat. Fatal overdoses are rare, but are still reported on occasion. These include cases of accidental exposure, suicide, and excessive intentional exposure.
There are limited and conflicting data on the pharmacokinetics of DNP in humans. The EPA states that "Data on the elimination kinetics of the dinitrophenols or their metabolic products in humans were not found." The ATSDR's Toxicological Profile for Dinitrophenols also states that "No studies were located regarding distribution in humans after oral exposure to 2,4-DNP. Limited information is available regarding distribution in animals after oral exposure to 2,4-DNP." However, they do state that "Elimination from the body appears to be rapid, except possibly in cases of compromised liver function." This coincides with a review in the NEJM on the biological actions of dinitrophenol, which stated that "Judging from the metabolic response, DNP appears to be eliminated entirely in three or four days; in the presence of liver or kidney damage it is possible that the drug will be retained over a longer period." Oddly, more recent papers give an array of possible half-lives, ranging from 3 hours, to 5–14 days. Other recent papers maintain that the half-life in humans is unknown.
Although further investigation is needed, one case report notes that dinitrophenol-induced hyperthermia has been successfully resolved with dantrolene
administration. "Dinitrophenol uncouples oxidative phosphorylation, causes release of calcium from mitochondrial stores and prevents calcium re-uptake. This leads to free intracellular calcium and causes muscle contraction and hyperthermia. Dantrolene inhibits calcium release from the sarcoplasmic reticulum which reduces intracellular calcium. The resulting muscle relaxation allows heat dissipation. There is little risk to dantrolene administration. Since dantrolene may be effective in reducing hyperthermia caused by agents that inhibit oxidative phosphorylation, early administration may improve outcome."
While DNP itself is considered by many to be too risky for human use, its mechanism of action remains under investigation as a potential approach for treating obesity. Currently, research is being conducted on uncoupling protein
s naturally found in humans.
. It has been found in 61 of 1400 priority sites that need clean-up of industrial waste. It can enter the air from automobile exhaust, burning of certain industrial substances, and from reaction of nitrogen in air with other atmospheric chemicals. The major site of degradation is the soil, where microorganisms metabolize it.
However, the effects of DNP on anaerobic
micro-organisms are still largely undetermined. Some studies suggest that there is anaerobic toxicity due to a reduced methane production.
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
poison. It uncouples
Uncoupling protein
An uncoupling protein is a mitochondrial inner membrane protein that can dissipate the proton gradient before it can be used to provide the energy for oxidative phosphorylation.There are five types known in mammals:* UCP1, also known as thermogenin* UCP2...
oxidative phosphorylation
Oxidative phosphorylation
Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate . Although the many forms of life on earth use a range of different nutrients, almost all aerobic organisms carry out oxidative phosphorylation to produce ATP,...
by carrying protons across the mitochondrial membrane, leading to a rapid consumption of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
without generation of ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
.
Dinitrophenols as a class of compounds, of which there are six members, do not occur naturally but are all manufactured compounds.
Chemical properties
2,4-Dinitrophenol is a yellow, crystalline solid that has a sweet, musty odor. It sublimes when carefully heated and is volatile with steam. It is soluble in ethyl acetateEthyl acetate
Ethyl acetate is the organic compound with the formula CH3COOCH2CH3. This colorless liquid has a characteristic sweet smell and is used in glues, nail polish removers, and cigarettes...
, acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
, chloroform
Chloroform
Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
, pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
, carbon tetrachloride
Carbon tetrachloride
Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...
, toluene
Toluene
Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...
, alcohol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
, benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
, and aqueous alkaline solutions. Its crystalline sodium salts are also soluble in water. It forms explosive salts with alkalies and ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, and emits toxic fumes of nitrogen oxides when heated to decomposition. It is incompatible with heavy metals and their compounds.
Uses
Commercial DNP is primarily used for scientific research and in manufacturing. It has been used at times to make dyeDye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
s, other organic chemicals, and wood preservatives. It has also been used to make photographic developer, explosives, and pesticides.
Pharmacological action
In living cells, DNP acts as a proton ionophoreIonophore
An ionophore is a lipid-soluble molecule usually synthesized by microorganisms to transport ions across the lipid bilayer of the cell membrane...
, an agent that can shuttle protons (hydrogen ions) across biological membranes. It defeats the proton gradient across mitochondria and chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
membranes, collapsing the proton motive force that the cell uses to produce most of its ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
chemical energy. Instead of producing ATP, the energy of the proton gradient is lost as heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
.
DNP is often used in biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
research
Research
Research can be defined as the scientific search for knowledge, or as any systematic investigation, to establish novel facts, solve new or existing problems, prove new ideas, or develop new theories, usually using a scientific method...
to help explore the bioenergetics
Bioenergetics
Bioenergetics is the subject of a field of biochemistry that concerns energy flow through living systems. This is an active area of biological research that includes the study of thousands of different cellular processes such as cellular respiration and the many other metabolic processes that can...
of chemiosmotic
Chemiosmosis
Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration....
and other membrane transport
Membrane transport
In cellular biology the term membrane transport refers to the collection of mechanisms that regulate the passage of solutes such as ions and small molecules through biological membranes namely lipid bilayers that contain proteins embedded in them...
processes.
Dieting aid
DNP was used extensively in diet pills from 1933 to 1938 after Cutting and Tainter at Stanford University made their first report on the drug's ability to greatly increase metabolic rate. After only its first year on the market Tainter estimated that probably at least 100,000 persons had been treated with DNP in the United States, in addition to many others abroad. DNP acts as a protonophoreProtonophore
A protonophore, also known as a proton translocator, is an ionophore that allows protons to cross lipid bilayers. This would otherwise not occur as protons have positive charge and hydrophilic properties, making them unable to cross without a channel or transporter...
, allowing protons to leak across the inner mitochondrial membrane and thus bypass ATP synthase
ATP synthase
right|thumb|300px|Molecular model of ATP synthase by X-ray diffraction methodATP synthase is an important enzyme that provides energy for the cell to use through the synthesis of adenosine triphosphate . ATP is the most commonly used "energy currency" of cells from most organisms...
. This makes ATP energy production less efficient. In effect, part of the energy that is normally produced from cellular respiration is wasted as heat. The inefficiency is proportional to the dose of DNP that's taken. As the dose increases and energy production is made more inefficient, metabolic rate increases (and more fat is burned) in order to compensate for the inefficiency and meet energy demands. DNP is probably the best known agent for uncoupling oxidative phosphorylation
Oxidative phosphorylation
Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate . Although the many forms of life on earth use a range of different nutrients, almost all aerobic organisms carry out oxidative phosphorylation to produce ATP,...
. The production or "phosphorylation
Phosphorylation
Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes....
" of ATP by ATP synthase gets disconnected or "uncoupled" from oxidation. Interestingly, the factor that limits ever-increasing doses of DNP is not a lack of ATP energy production, but rather an excessive rise in body temperature due to the heat produced during uncoupling. Accordingly, DNP overdose will cause fatal hyperthermia
Hyperthermia
Hyperthermia is an elevated body temperature due to failed thermoregulation. Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate...
. In light of this, it's advised that the dose be slowly titrated according to personal tolerance, which varies greatly. Case reports have shown that an acute administration of 20–50 mg/kg in humans can be lethal. Concerns about dangerous side-effects and rapidly developing cataracts resulted in DNP being discontinued in the United States by the end of 1938. DNP, however, continues to be used by some bodybuilders
Bodybuilding
Bodybuilding is a form of body modification involving intensive muscle hypertrophy. An individual who engages in this activity is referred to as a bodybuilder. In competitive and professional bodybuilding, bodybuilders display their physiques to a panel of judges, who assign points based on their...
and athletes to rapidly lose body fat. Fatal overdoses are rare, but are still reported on occasion. These include cases of accidental exposure, suicide, and excessive intentional exposure.
There are limited and conflicting data on the pharmacokinetics of DNP in humans. The EPA states that "Data on the elimination kinetics of the dinitrophenols or their metabolic products in humans were not found." The ATSDR's Toxicological Profile for Dinitrophenols also states that "No studies were located regarding distribution in humans after oral exposure to 2,4-DNP. Limited information is available regarding distribution in animals after oral exposure to 2,4-DNP." However, they do state that "Elimination from the body appears to be rapid, except possibly in cases of compromised liver function." This coincides with a review in the NEJM on the biological actions of dinitrophenol, which stated that "Judging from the metabolic response, DNP appears to be eliminated entirely in three or four days; in the presence of liver or kidney damage it is possible that the drug will be retained over a longer period." Oddly, more recent papers give an array of possible half-lives, ranging from 3 hours, to 5–14 days. Other recent papers maintain that the half-life in humans is unknown.
Although further investigation is needed, one case report notes that dinitrophenol-induced hyperthermia has been successfully resolved with dantrolene
Dantrolene
Dantrolene sodium is a muscle relaxant that acts by abolishing excitation-contraction coupling in muscle cells, probably by action on the ryanodine receptor. It is the only specific and effective treatment for malignant hyperthermia, a rare, life-threatening disorder triggered by general anesthesia...
administration. "Dinitrophenol uncouples oxidative phosphorylation, causes release of calcium from mitochondrial stores and prevents calcium re-uptake. This leads to free intracellular calcium and causes muscle contraction and hyperthermia. Dantrolene inhibits calcium release from the sarcoplasmic reticulum which reduces intracellular calcium. The resulting muscle relaxation allows heat dissipation. There is little risk to dantrolene administration. Since dantrolene may be effective in reducing hyperthermia caused by agents that inhibit oxidative phosphorylation, early administration may improve outcome."
While DNP itself is considered by many to be too risky for human use, its mechanism of action remains under investigation as a potential approach for treating obesity. Currently, research is being conducted on uncoupling protein
Uncoupling protein
An uncoupling protein is a mitochondrial inner membrane protein that can dissipate the proton gradient before it can be used to provide the energy for oxidative phosphorylation.There are five types known in mammals:* UCP1, also known as thermogenin* UCP2...
s naturally found in humans.
Environmental toxicity
DNP is considered an important environmental contaminant by the United States Environmental Protection AgencyUnited States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
. It has been found in 61 of 1400 priority sites that need clean-up of industrial waste. It can enter the air from automobile exhaust, burning of certain industrial substances, and from reaction of nitrogen in air with other atmospheric chemicals. The major site of degradation is the soil, where microorganisms metabolize it.
However, the effects of DNP on anaerobic
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
micro-organisms are still largely undetermined. Some studies suggest that there is anaerobic toxicity due to a reduced methane production.