Antibacterial, antifungal, antiviral and antioxidant activities. It is an analgesic and an anti-inflammatory agent, with antihepatotoxic, antiulcerogenic and clastogenic activities also. It inhibits platelet aggregation in vitro and gonadotropin release, and affects both DNA binding and prostaglandin induction.

(+)-Catechin; Catechinic acid; Catechol; Catechuic acid; (+)-Cyanidanol; (+)-Cyanidan-3-ol
Widespread occurrence in nature, especially in woody plants, e.g., in willow catkin, Salix caprea.

Biologically highly active. It is used as a haemostatic drug, and in the treatment of various liver diseases, especially acute hepatitis. It shows strong liver protective and potent antiperoxidative activities, so that it may act as a "radical scavenger" by neutralizing free radicals produced by hepatotoxic substances. However, prolonged treatment with (+) catechin can induce several adverse reactions, most of them immunomediated, such as haemolysis, acute renal failure and skin rashes.

Kaempferol; 3, 5, 7, 4'-Tetrahydroxyflavone
Very widespread occurrence, both free and bound as glycosides. The 3-arabinofuranoside, juglanin, and 3-rhamnofuranoside occur in the leaves and flowers of Aesculus hippocastanum. The 3-rhamnopyranoside, afzelin, occurs in the heartwood of Afzelia spp. , and the 3-galactoside trifolin, occurs in the leaves of Trifolium pratense .

Radical scavenger. It shows anti-inflammatory, antibacterial and mutagenic activities. It inhibits the proliteration of rat Iymphocytes at a concentration of 10 J M. Also, it inhibits iodothyronine deiodinase, :5-lipoxygenase, and ionophore-induced arachidonlc acid release and metabolism.

Luteolin; 5, 7, 3', 4'-Tetrahydroxyflavone
Very widespread occurrence, especially as the 7-glucoside and 7-glucuronide, e.g., in the petals of Antirrhinum majus . The 7-galactoside and 7-rutinoside occur in Capsella bursa-pastoris, the 3'-glucoside in Dracocephalum thymiflorum , and the 4'-glucoside in the flowers of Spartium junceum . The aglycone is also very common, especially in leaf exudates.

Anti-inflammatory and antibacterial activities. It inhibits iodothyronine deiodinase, protein kinase C, NADH-oxidase, succinoxidase, lens aldose reductase, etc. It acts as a nodulation signal to the bacterium Rhizobium leguminosarum in pea roots and the bacterium R. meliloti in lucerne.

Procyanidin; Proanthocyanidin A2; Epicatechin
Occurs in the nuts of Cola acuminata, the berries of Vaccinium vitis-idaea, and the fruits of the horse-chestnut, Aesculus hippocastanum and Persea gratissima.

Quercetin;; 3, 5, 7, 3', 4'-Pentahydroxyflavone
The commonest flavonoid in higher plants, usually present in glycosidic form, but also isolated free from the families Compositae, Passiflorae, Rhamnaceae and Solanaceae.

Inhibits many enzymes, e.g., protein kinase C, lipogenases, lens aldose reductase, 3', 5'-cyclic adenosine monophosphate phosphodiesterases. It is a radical scavenger. Quercetin also inhibits smooth muscle contraction, and proliferation of rat Iymphocytes. It is antigonadotropic, anti inflammatory, antibacterial, antiviral and antihepatotoxic, and shows some mutagenic activity and allergenic properties.