Antioxidant, Cytotoxic and Phytotoxic activities of Schumacheria castaneifolia, a plant endemic to Sri Lanka

Abstract

Investigation of the bioactivity of plants and their constituents is an important step in the discovery of novel drugs. The genus Schumacheria belonging to the family Dilleniaceae is endemic to Sri Lanka and contains three species, S. castaneifolia, S. alnifolia and S. angustifolia. There has been no systematic search for bioactive agents from the genus Schumacheria. This paper describes antioxidant, cytotoxic and phytotoxic properties of S. castaneifolia. The plant was collected from Thummodara in the Sabaragamuwa Province. Air- dried leaves, root-bark and stem-bark were separately extracted into methanol and dichloromethane, and the extracts were tested for antioxidant activity using the 2,2- diphenyl-1-picrylhydrazyl assay, cytotoxicity using the brine shrimp (Artemia salina) assay and phytotoxicity using the lettuce (Lactuca sativa) seed assay. In the antioxidant assay the ICso values of methanol extracts of the stem-bark, root-bark and leaves were 11, 7.6 ppm and 9.2 ppm, respectively; the dichloromethane extracts had relatively low activity with the corresponding IC50 values at 212.2 ppm, 196.4 ppm and 210.5 ppm. The antioxidant activity of the known antioxidant, (±)-a-tocopherol showed an IC50 value of 11.4 ppm. Methanol and dichloromethane extracts of the stem bark, root-bark and leaves showed low cytotoxic activity having LC50 values for methanolic extracts at 903.8 ppm, 81.6 ppm and 66.0 ppm and for dichloromethane extracts at 74.4 ppm, 30.9 ppm and 340.1 ppm, respectively. A lactone isolated from a Hortonia sp. in a previous study was used as a positive reference control and showed an LC50 value of 0.14 ppm. Phytotoxicity assay revealed root inhibition of 80.2% and shoot inhibition of 83.9% for the dichloromethane leaf extract at 2000 ppm level while the corresponding values for the methanolic extracts were 28.7% and 35.5%, respectively.