Protocatechuic acid

• Protocatechuic
• 3,4- dihydroxybenzoic acid

Light brown solid

Fixed

202-204 ° C ( decomposition)

4.48 (25 ° C)

Poorly in water (20 g · l-1 at 20 ° C)

Attention

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Protocatechuic (3,4- dihydroxybenzoic acid ) is an aromatic compound which is derived both from the benzoic acid as well as from catechol (1,2- dihydroxybenzene ). The structure consists of a benzene ring with an attached carboxy (-COOH) and two hydroxy groups (-OH) as a substituent. It belongs to the group of dihydroxybenzoic acids, is in the free form in the fruits of Japanese star anise ' ( Illicium religiosum ) and is formed in the alkali fusion of numerous natural products, for example, catechins, of various resins, the dye Maklurin and several anthocyanins.

Occurrence

Protocatechuic acid is present in edible vegetables, fruits and nuts, such as olive, brown rice and pecans.

Representation

Chemical Synthesis

Synthetic provides you represent protocatechuic of p -hydroxybenzoic acid; This is carried on in the m- chloro-p -hydroxybenzoic acid and the latter is heated with potassium hydroxide under pressure.

The carboxylation with a Kolbe -Schmitt reaction by heating catechol with ammonium carbonate in a closed tube gives only poor yields in aqueous solution, no reaction takes place.

A further synthesis starts from vanillin, and performs on the demethylation of vanillic acid and its potassium salt for protocatechuic:

When heating Piper Only acid with hydrochloric acid or hydroiodic acid is also formed protocatechuic acid. As a by-product formaldehyde is formed.

Biosynthesis

Protocatechualdehyde can be enzymatically oxidized to protocatechuic acid.

Properties

Protocatechuic acid and melts at about 202-204 ° C and decomposes it by decarboxylation to catechol and carbon dioxide. Their aqueous solution is blue-green on the addition of ferric chloride. These color changes after addition of a little soda or ammonia after purple, then red in order. Protocatechuic acid is highly reducing.

Reactions

With elemental bromine formed at room temperature for 5 Bromprotocatechusäure which is converted to gallic acid by fusion with potassium carbonate.

Bromination is carried out at 100 ° C with elimination of carbon dioxide produced Tetrabrombrenzcatechin.

Physiological significance

The effect of protocatechuic acid on living cells is currently the subject of research and is still discussed controversially. It has been shown that it is a potent antioxidant, with an approximately 10-fold greater activity than α -tocopherol. In high doses, however, for example 10 mM, but it can also induce oxidative stress in cell cultures.

Compared with cancer cells shows protocatechuic different effects. In human gastric cancer cells ( cells of a Magenadenokarzinoms ) and other tumor cells of the digestive tract, it induces apoptosis and therefore acts in the sense of a cancer agent. There are however also study data that indicate an adverse effect of protocatechuic acid. So it induces cell division in neural stem cells and blocked apoptosis there. Also in skin cancer cells of the mouse has been observed. If there were induced chemically by 12-O- tetradecanoylphorbol - 13-acetate cancers cells, protocatechuic could even enhance tumor formation. If you generated in vitro malignant cell lines of human submandibular gland, protocatechuic could not kill these cancer cells.