Screening of antioxidant and antifungal properties of extracts from endemic Soqotran medicinal plants

ABSTRACT

A total of 50 different extracts from 18 endemic Soqotran medicinal plants belonging to 12 plant families were screened for their antioxidant activity, using the DPPH free radical scavenger assay and their antifungal activity against the phytopathogenic fungus Cladosporiumn cucumerinum, using a microbioassay on TLC plates. Of the extracts tested, 8 out of 25 methanol extracts showed more than 50% antioxidative activity at a concentration of 200 microg/ml. Extracts of Kalanchoe farinaceae, Caralluma socotrana, and Boswellia socofrana were the most active ones. Nine out of 50 extracts exhibited a fungitoxic activity. Chloroform extracts of Pulicaria stephanocarpa leaves and roots showed at an application amount of 400 micrg inhibition zones of 20 +/- 1.0 and 18 +/- 0.7 mm, respectively. The chloroform extract of Kalanchoe farinaceae leaves exhibited stronger antifungal activity [18 +/- 0.8 mm inhibition zone] than the methanolic extract [15 +/- 0.3 mm inhibition zone]. The most active methanolic extract was obtained from Acridocarpus socotranus leaves, with a 18 +/- 0.4 mm inhibition zone for 400 microgm applied