Flavan-3-ols Isolated from Some Medicinal Plants Inhibiting COX-1 and COX-2 Catalysed Prostaglandin Biosynthesis

Abstract

Extracts from the four plant species Atuna racemosa Raf. ssp. racemosa, Syzygium corynocarpum (A. Gray) C. Muell., Syzygium malaccense (L.) Merr. & Perry and Vantanea peruviana Macbr., traditionally used for inflammatory conditions, were fractionated using a cyclooxygenase-1 catalysed prostaglandin biosynthesis in vitro assay. The flavan-3-ol derivatives (+)-cate-chin, (+)-gallocatechin, 4′-O-Me-ent-gallocatechin, ouratea-cat-echin and ouratea-proanthocynidin A were isolated as active principles. The IC₅₀ values ranged from 3.3 µM to 138 µM whilst indomethacin under the same test conditions had an IC₅₀ value of 1.1 µM. The flavonol rhamnosides mearnsitrin, myricitrin and quercitrin were also isolated. When further tested for inhibitory effect on cyclooxygenase-2 catalysed prostaglandin biosynthesis, the five flavan-3-ol derivatives exhibited from equal to weaker inhibitory potencies, as compared to their cyclooxygenase-1 inhibitory effects. The flavonol rhamnosides were inactive towards both enzymes.

Key words

Atuna racemosa ssp. racemosa - Chrysobalanaceae - Syzygium corynocarpum - Syzygium malaccense - Myrtaceae - Vantanea peruviana - Humiriaceae - flavan-3-ols - flavonol rhamnosides - anti-inflammatory activity - prostaglandin biosynthesis - cyclooxygenase-1 (COX-1) - cyclooxygenase-2 (COX-2)