Description
Pyrogallol is a natural oxidant that can generate superoxide (O
2-) in alkaline solutions through autoxidation to a semiquinone radical. Importantly, the semiquinone radical can react with O
2- in an acidic environment to produce a quinone and H
2O
2. Pyrogallol autoxidation is used in superoxide dismutase activity assays. It can also be used in assays to assess antioxidant capacity. Pyrogallol is used in some biological systems as an O
2- scavenger. In other biological systems, it is used as an O
2- generator. Pyrogallol effectively scavenges DPPH radical and ABTS
+ in vitro. Pyrogallol is a product of tannin degradation to gallic acid by ruminant microbes and has hepatotoxic and nephrotoxic effects
in vivo.
Chemical Properties
white crystalline solid
Chemical Properties
White or nearly white needle- or
leaf-shaped crystals or crystalline powder.Pyrogallol is practically odorless.
Uses
Complexing agent; reducing agent; alkaline solution indicator for gaseous oxygen.
Uses
Pyrogallol is used in the manufacture of various dyes; in dyeing furs, hairs, and feathers; for staining leather; in engraving;as a developer in photography; and as an analytical reagent..
Uses
Pyrogallol possesses importance as a spectrophotometric reagent in the determination of niobium and tantalum. The absorptions of niobium and tantalum complexes are usually measured at 340 and 335 nm, respectively. The niobium complex is formed in slightly acidic medium, and the tantalum complex in strongly acidic medium (4 N HC1). The absorption spectra are pH-dependen.
Production Methods
Pyrogallol is prepared by heating dried gallic acid at about
200°C with the loss of carbon dioxide or by the
chlorination of cyclohexanol to tetrachlorocyclohexanone,
followed by hydrolysis.
Definition
ChEBI: A benzenetriol carrying hydroxy groups at positions 1, 2 and 3.
General Description
Odorless white to gray solid. Sinks and mixes with water.
Air & Water Reactions
Turns gray on exposure to light or air. Water soluble.
Reactivity Profile
Pyrogallol is a strong reducing agent. Reacts with alkalis, NH3, antipyrine, camphor, phenol, iron and lead salts, iodine, lime water, menthol and KMnO4.
Hazard
Toxic by ingestion and skin absorption.
Health Hazard
Inhalation of dust causes irritation of nose and throat. Ingestion may cause severe gastrointestinal irritation, convulsions, circulatory collapse, and death. Contact with eyes causes irritation. Skin contact can cause local discoloration, irritation, eczema, and death; repeated contact can cause sensitization.
Health Hazard
The toxic symptoms are similar to those of phenol. It can enter the body by absorption through skin and ingestion. The poisoning effects are nausea, vomiting, gastritis, hemolysis, methemoglobinemia, kidney and liver damage, convulsions, and congestion of lungs. High doses can cause death. Ingestion of 2–3 g of solid can be fatal to humans. The LD50 values varied widely in species. The oral LD50 value in mice is about 300 mg/kg.
Fire Hazard
Pyrogallol is probably combustible.
Contact allergens
Pyrogallol belongs to the phenols group. It is an old
photograph developer and a low sensitizer in hair dyes.
Biochem/physiol Actions
Pyrogallol also referred to as 1,2,3-trihydroxybenzene inhibits the response to nitric oxide (NO) in the rat anococcygeus muscle.
Safety Profile
Human poison by ingestion and subcutaneous routes. An experimental poison by ingestion, subcutaneous, intravenous, and intraperitoneal routes. Experimental teratogenic and reproductive effects. Questionable carcinogen with experimental tumorigenic data. Mutation data reported.
1 198 PPRSOO PYROSULFURYL CHLORIDE
Readdy absorbed through the skin. Human systemic effects by ingestion: convulsions, dyspnea, gastrointestinal effects. A severe skin and eye irritant. Incompatible with alkalies, NH3, antipyrine, phenol, iron and lead salts, iodine, KMn04. When heated to decomposition it emits acrid smoke and irritating fumes. Used as a topical antibacterial agent, as an intermediate, hair dye component, and analytical reagent.
Carcinogenicity
Pyrogallol was not carcinogenic
in mouse and rabbit chronic dermal studies. Mice were
treated twice weekly with pyrogallol in acetone (50%) on
the shaved flank for life. There was no increase in dermal or
systemic tumors. A similar study in rabbits also
revealed no skin tumors, although positive controls showed
an increase in tumors in both mice and rabbits.
Pyrogallol was considered to be cocarcinogenic when
administered dermally three times a week together with
the skin carcinogen benzo[a]pyrene for 440 days;
pyrogallol administered alone caused no increase in skin
tumors.
