Abstract
Ethnopharmacologic approaches offer new insights into traditional medicine and frequently reveal new structures or sources of natural products. 34 different plants used in Yemeni traditional medicine were collected mainly on the island of Soqotra. 63 methanolic and hot-aqueous extracts were tested for their antioxidant activity and in vitro cytotoxicity against two human cancer cell lines (MCF-7 and 5637).
5 aqueous extracts and 11 methanolic extracts exhibited remarkable radical scavenging effects. Extracts of
Phargamanthera regularis, Myrtus communis
and
Rosmarinus officinalis
showed strong antioxidant activity at concentrations less than 50µg/ml.
11 methanolic and one aqueous plant extract were shown to be cytotoxic to one or both cell lines. The methanolic extract of
Hypoestes forskalei
showed the strongest cytotoxicity against both cell lines with IC
50
values of 14.3µg/ml for 5637 and 32.1µg/ml for MCF-7. The methanolic and the sole active aqueous extract of
Pergularia tomentosa
showed cytotoxic activity against 5637 cell line with IC
50
values of 21.5 and 39.1µg/ml. Another three methanolic extracts showed strong cytotoxic activity against 5637 cell line with IC
50
values between 40 and 48µg/ml, two of them where also moderately toxic for MCF-7.
The most promising plant extracts will be investigated further and may be a potential source for new anticancer drugs while others are cytoprotective and may be used in skin-protecting formulations. Purification and structure elucidation of the natural products responsive for the activities measured are underway.