Protocatechuic acid, oxidation

Piperonylic acid has been made by the oxidation of piperic acid,1 piperonal,1 safrole2 and isosafrole2 with potassium permanganate. It has also been prepared by the action of methylene iodide on protocatechuic acid 3 in the presence of alkali. 

Wang et al. (62) reported the oxidative polymerization of a mixture of phenolic compounds in aqueous solution containing mont-morillonlte, illite, and kaolinite, each of which had been mixed with quartz in a 3 7 ratio, and by quartz alone. The mixture of phenolic compounds contained gallic acid, pyrogallol, protocatechuic acid, caffeic acid, orcinol, ferulic acid, p-coumaric acid, syringic acid, vanillic acid, and p-hydroxybenzoic acid. The oxidative... 

When the effects of UV/ozone treatment on the degradation of protocatechuic acid were compared with the rates of six other advanced oxidation processes (AOPs), the UV/ozone process ranked second behind only the UV /03/H202 process in terms of oxidation kinetics. The combination of UV irradiation and ozone was more effective than either UV or ozone alone in terms of degradation rates of protocatechuic acid. The contribution of different reaction pathways in a combined system will be discussed in detail in Chapter 14. 

Heuser was also a pioneer in certain of his researches. He was one of the first to show that some types of oxidized cellulose, when treated with mineral acids, give carbon dioxide, thus indicating that carboxyl groups are present. In his studies on lignin, he educed evidence that this system might contain aromatic groups alkaline fusion of sprucewood lignin yielded protocatechuic acid and pyrocatechol, and Heuser and his coworkers obtained extensive (juantitative data in this area. Another early piece of work involved the preparation of purified xylan from straw. 

Protocatechuic Aldehyde.—A di-phenol aldehyde, viz., the 3-4-di-hydroxy benzaldehyde, is known as protocatechuic aldehyde because it yields protocatechuic acid on oxidation. 

Protocatechuic Acid.—One of the di-hydroxy benzoic acids is related to vanillin, which we have already studied. The acid is known as protocatechuic acid, and derives its name from the fact that it may be obtained from a gum or resin, known as gum catechin by fusion with potash, i.e. by heat and oxidation in presence of an alkali. A large variety of plant products including alkaloids essential oils, gums, resins and tannins yield this acid. The following may be mentioned gum catechin, gum benzoin, guaiac resin, myrrh, piperine or piperic acid, vanillin, cafe-tannic acid. These natural sources at once suggest a relationship to vanillin (p. 661) and heliotropin (p. 662). It is the acid corresponding to protocatechuic aldehyde, 3-4-di-hydroxy benzal-dehyde (p. 661), which explains the relationship just mentioned. Its constitution, is then ... 

The antioxidant effects of natural phenols in olive oils was studied by Papadopoulos [46], adding extracts of a VOQ, having polyphenols, to a sophisticated bleaching oil, washed-out of phenolic antioxidants and evidenced a significant inhibition of auto-oxidation over time in comparison with samples without such an addition. On the other hand, it has revealed that this effect is more pronounced in hydroxy-tyrosol than caffeic acid and protocatechuic acid... 

From the cinnamic acids or phenyl propanoids described above, / -oxidation and truncation of side chains yields a variety of benzoic or simple phenolic acids [28], Rao et al., [22] identified gallic acid (18), gentisic acid (19), protocatechuic acid (20), />-hydroxybenzoic acid (21), oc-resorcyclic acid (22), vanillic acid (23) and salicylic acid (24) in C. arietinum and showed that overall, leaf content of all phenolic compounds was much greater than in roots and stem. They postulated that the production of these compounds may enhance the activity of indole acetic acid oxidase or may express antimicrobial properties when leached into the soil. However, Singh et al. [24] showed that the production of both 18 and 24 by C. arietinum was induced when treated by the culture filtrate of Sclerotium rolfsii along with the phenyl propanoids 14, 15 and 17 mentioned above. 

Protocatechuic acid is soluble in water, and melts at 199°. Ferric chloride colors its aqueous solution bluish-green, the color changing to blue and finally to red on the addition of alkalies. The acid reduces an ammoniacal solution of silver nitrate, but does not reduce Fehling s solution. It decomposes into pyrocatechol and carbon dioxide when distilled. Bromine in the cold forms bromoprotocatechuic acid at 100° the carboxyl group is eliminated and tetrabromopyrocatechol is formed. The monomethyl ether, C6H3(OH)(OCH3)COOH(4, 3, 1), is called vanillic acid, as it is formed by the oxidation of vanillin. The dimethyl ether, veratric acid, and the methylene ether, CH2 02 C6H3C00H, piperonylic add, are obtained from a number of substances which occur in nature. 

Yamane et al.[13] determined cobalt in sea water and river waters with a catalytic spectrophotomeiric method after on-line preconcentration using a column packed with quinolin-8-ol immobilized on silica gel. The tartrate eluate from the preconcentraiion had to pass through a second column packed with a strongly acidic cation exchanger to remove iron(III) and manganese(II) which interfere in the catalytic reaction of oxidation of protocatechuic acid by hydrogen peroxide. An extremely low detection limit of 0.005 /ig 1 was obtained. However, the sampling frequency was less than 2 h . ... 

Chemoprevention of 4-nitroquinolme 1-oxide-induced oral carcinogenesis by dietary protocatechuic acid during initiation and postinitiation phases. Cancer Res., 54, 2359-2365,... 

Nakamura, Y., Torikai, K., and Ohigashi, H., A catechol antioxidant protocatechuic acid pententiates inflammatory leukocyte-derived oxidative stress in mouse skin via a tyrosinase bioactivation pathway. Free Radical Biol. Med., 30, 967-978, 2001. 

Protocatechuic aldehyde, protocatechuic acid, catechol (D 22.2.5) Constituents of onion bulbs and bananas, oxidized after infection to the corresponding fungitoxic o-quinones... 

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