Bioactivity guided isolation studies on Hypericum microcalycinum

The genus Hypericum L. (Hypericaceae) is represented by 100 taxa grouped under 19 sections 45 of which are endemic in Turkey Hypericum species are used as antispasmodic, sedative and antihelmintic internally; antiseptic and for wound healing externally in Anatolia [1,2]. They contain mainly hyperforins, naphthodianthrones, flavonoids, tannins, xanthones, essential oils [3]. In the present study, bioguided isolation were performed on the aqueous extract of Hypericum microcalycinum Boiss. & Heldr. on the basis of 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and superoxide (SO) radical scavenging activities. The aqueous extract was subjected to polyamide column chromatography to afford eight main fractions. Aqueous extract and polyamide column fractions were tested for their radical scavenging activities and fraction E was found the most active one. Repeated column chromatografies of the fraction E resulted in the isolation of two catechins and three flavonoid glycosides. The structures of the isolated compounds were identified as catechin and epicatechin [1], apigenin-6-C-2''-O-acetyl glucopyranoside [2], quercetin-3-O-glucopyranoside [3] and quercetin-3-O-arabinopyranoside [4] on the basis of spectroscopic (1D/2D NMR and FAB-MS) data. Radical scavenging activities of compounds were also tested. While compound 1, a mixture of catechin and epicatechin, was found the most effective compound, their activity was found comparable to that of known antioxidant, ascorbic acid.

Acknowledgement: US Harput has been supported by TUBA-GEBIP (USH/2013) Award program.

References:

[1] Davis PH, Flora of Turkey and the East Aegean Islands, Volume 2, University Press, Edinburgh (1966).

[2] Baytop T, Therapy with Medicinal Plants in Turkey (Past and Present), Publications of Istanbul University, No:3, Istanbul, 1984, p166.

[3] Özkan EE, Mat A. An overview on Hypericum species of Turkey, J Pharmacognosy Phytotherapy, 2013; 5: 38 – 46.