Polyphenolic compounds and in vitro antimicrobial and antioxidant activity of aqueous extracts from leaves of some Cirsium species.

Crude aqueous extracts from leaves of Cirsium arvense, C. oleraceum, C. palustre, C. rivulare and C. vulgare were investigated. The content of tannins in mentioned sources, determined by the weight method with hide powder, varied between 1 and 7.63%. Total phenolic content, analysed by using Folin-Ciocalteau's method, ranged between 54 and 96 mg g(-1), was expressed as milligrams of gallic acid per gram of dry extract. Phenolic acids were identified by HPLC method. Antimicrobial activity of those extracts was examined. Cirsium palustre extract was the most active against investigated microorganisms. It was observed that the content of small-molecular phenolic compounds had greater influence on the activity of extracts than tannins. The total antioxidant activity indicated by radical cation 2,2'-azini-di-(3-ethylbenzthiazoline sulphonate) ABTS(*+), expressed as total antioxidant status (TAS) ranged from 2.31 to 2.78 mM L(-1).