Antioxidative activities of water extracts of some Malaysian herbs
This study was conducted on selected local herbs such as ulam raja (Cosmos caudatus), kesum (Polygonum minus), selom (Oenanthe javanica), pegaga (Centella asiatica) and curry leaves (Murraya koenigii) to investigate their antioxidative activities. The water extracts of the herbs were analysed for total phenolic content, reducing antioxidant power, ferric thiocyanate (FTC) and the thiobarbituric acid (TBA) test was also accried out. Polygonum minus showed the highest total phenolic content and reducing power among the herbs. Increasing the concentration of the extracts resulted in increased Fe3+ reducing antioxidant power for all the herbs. FTC and TBA tests on the extracts during seven days of storage showed that all the herbs extracts had the ability to reduce oxidation compared to the control (P < 0.05). From the FTC analysis, Murraya koenigii leaves was best in reducing the oxidation rate (67.67%) compared to the other herbs studied. Analysis of TBA showed that Centella asiatica extract had the highest antioxidant effect. However, both TBA and FTC analysis for these two herbs showed no significant difference (P > 0.05) from Polygonum minus and butylated hydroxyanisole (BHT) a synthetic antioxidant. Correlation analysis showed positive correlations between amount of total phenolic content and reducing power (r = 0.75) and antioxidative activities (r = 0.58) in linoleic acid emulsion system. This shows that antioxidative activities of these Malaysian herbal plants especially Polygonum minus may be a potential source of natural antioxidants with similar characteristics to the synthetic antioxidant, BHT.