Pyrogallol

Description

Pyrogallol is a natural oxidant that can generate superoxide (O₂^-) in alkaline solutions through autoxidation to a semiquinone radical. Importantly, the semiquinone radical can react with O₂^- in an acidic environment to produce a quinone and H₂O₂. 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 O₂^- scavenger. In other biological systems, it is used as an O₂^- 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.

The Uses of Pyrogallol

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.

The Uses of Pyrogallol

Complexing agent; reducing agent; alkaline solution indicator for gaseous oxygen.

The Uses of Pyrogallol

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..

What are the applications of Application

Pyrogallol is a metal-complexing benzene triol compound

Definition

ChEBI: A benzenetriol carrying hydroxy groups at positions 1, 2 and 3.

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.

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.