Antioxidant phenolics from Hypericum calycinum
The genus Hypericum (Hypericaceae) is represented by more than 70 species in the Flora of Turkey . Hypericum perforatum (St. John's worth) is well-known and widely used for the treatment of mild to moderate depression . It was reported that the effects of H. calycinum extract on the central nervous system of mice was almost equal to that of H. perforatum and was found as effective as the antidepressant drugs in animal models [3,4]. From the EtOAc and n-BuOH soluble fractions of the MeOH extract two caffeoylquinic acid derivatives (chlorogenic acid and butyl chlorogenate), seven flavonoids (quercetin, quercitrin, hyperoside, isoquercitrin, miquelianin, rutin and I3,II8-biapigenin) and two flavanols ((+)-catechin and (-)-epicatechin) were isolated. The structures of the compounds were established on the basis of mass spectrometry and NMR experiments. Free radical scavenging activities of the compounds were determined in in-vitro DPPH and nitric oxide (NO) scavenging models. Compounds showed strong DPPH and moderate NO scavenging activities in a concentration dependent manner. (+)-Catechin and (-)-epicatechin were found to be the most active compounds with IC50 values of 4.16 and 4.67µM for DPPH and 190 and 170µM for NO scavenging activities, respectively.
References: 1. Robson, N.K.B. (1967) Hypericum L. in: Flora of Turkey and East Aegean Islands Vol. 2 (Ed. Davis P.H.), University Press. Edinburgh.
2. Klingauf, P., et al. (2005) Phytochemistry 66: 139–145.
3. Öztürk, Y. (1997) Pharmacopsychiatry 30: 125–128.
4. Öztürk, Y. et al. (1996) Phytotherapy Res. 10: 700–702.