Antioxidant activity of polyphenolic compounds extracted from defatted raw and dry heated Tamarindus indica seed coat

The antioxidative properties and total phenolic contents of raw and dry heated seed coat of Tamarindus indica were examined. The raw and dry heated samples were extracted with methanol followed by 70% acetone, after treating with petroleum ether, solvents were removed using rotary vacuum evaporator and the extracts which contain residual moisture were freeze-dried, respectively. Methanol extracts for both raw and dry heated seed coat samples contained higher level of total phenolics and tannins than the aqueous acetone extracts. The extracts were screened for their potential antioxidant activities using such as O2−, OH, α,α-diphenyl-β-picrylhydrazyl (DPPH), ABTS+, FRAP and linoleic acid emulsion model systems. At different concentration of respective solvent extracts, the maximum level of superoxide anion radical scavenging activity (79–85%) was observed at 200 μg of both the raw and dry heated seed coat extracts in the reaction mixture. The DPPH radical and ABTS cation radical scavenging activities were well proved with the ferric reducing antioxidant capacity of the extracts. Interestingly, among the extracts, methanol and aqueous acetone extracts of dry heated sample showed the highest hydroxyl radical scavenging activity of 56.6 and 45.7%, respectively. All extracts, exhibited good antioxidant activity (64.5–71.7%) against the linoleic acid emulsion system and the values were lower and higher than the synthetic antioxdiant, BHA and ascorbic acid, respectively.