ANTIOXIDANT ACTIVITY OF METHANOLIC EXTRACT FROM SEED COAT OF MAJOR TAMARIND CULTIVATED IN THAILAND

Abstract

Methanolic extracts from the seed coat of five major tamarinds (TI-SP/P: Srichomphu, TI-STN/P: Sithong-nak, TI-STB/P: Sithong-bao, TI-PY/P: Priao-yak, TI-K/P: Khanti) cultivated in Thailand were investigated for antioxidative properties and content of total phenols. The content of total phenols in the extracts were determined by Folin- Ciocalteau’s method. Antioxidative activities of extracts were evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, anti-lipid peroxidation assay and reducing power. The strongest anti-lipid peroxidation activity (IC50 = 68.24 ug/mL) was found in the extract of TI-STB/P. Although all extracts showed higher anti-lipid peroxidation (IC50 between 68.24 and 311.53 ug/mL) compared to vitamin C (IC50 = 322.66 ug/mL), a different efficacy as reducing power and scavenging ability was observed. Extracts of TI-PY/P and TI-STB/P were found to have stronger reducing power compared to butylated hydroxyanisole (BHA) at concentration between 1-100 ug/mL, whereas highest radical scavenging activity was observed with the extract of TI-K/P (IC50 = 72.68 ug/mL). A statistically significant correlation (p < 0.05) between antioxidant activity and content of total phenols was not found. The results suggested that not only the amount of phenolic compounds but their chemical structures may also be important for the antioxidative activities. Furthermore, the seed coat extract of the TI-STB/P cultivar which showed marked antioxidant activities in most of the assays may be a potential source of natural antioxidant.