Antioxidant activity of seed coat extracts from Tamarind cultivars and topical preparation

Antioxidant and preliminary studied of antibacterial activity of tamarind seed coat extracts (TSCEs) were evaluated. Three tamarind cultivars, Tamarindus indica L. "Priao", "Srichomphu" and "Sithong-nak" were collected from Nakhon-Ratchasima Province. The seed coat of each cultivar was extracted by two solvent extraction systems. Solvent in System 1 was 70% ethanol, followed with chloroform and then ethyl acetate, respectively and solvent in System 2 was 70% ethanol and washed out lipid with chloroform. The extracts were dried to powder of TSCE. Higher percent yield of TSCEs at 54-62% in System 2 was obtained compared with TSCEs (15-18%) in System 1. Chemical analyses of the total phenolic compounds, tannin and proanthocyanidin were examined. HPLC technique was used for chemical fingerprint identification of TSCEs. HPLC chromatograms of TSCE of the 3 tamarind cultivars showed the similar pattern of peaks including peaks identical with reference standard (+)-catechin, procyanidin B2 and (-)-epicatechin. Antioxidant activity of TSCEs was evaluated by DPPH radical scavenging, reducing power, hydroxyl radical scavenging and anti-lipid peroxidation assays. Vitamin C and BHA were used as positive control. The EC50 values for TSCEs by each assay were determined. The results showed that TSCEs of the three tamarind cultivars possessed high antioxidant activity compared with the positive control. Antibacterial activity of TSCEs was preliminary studied against Staphylococcus aureus ATCC 6538P and Escherichia coli ATCC 25922 by broth microdilution method. MIC and MBC values against S. aureus for TSCEs were 0.39-1.5 mg/ml and 1.56-3.12 mg/ml, respectively; and against E. coli were 3.12-6.25 mg/ml and ?25 mg/ml, respectivel. TSCE of Tamarindus indica "Priao" in System 2 was used to develop a preparation of TSCE cream for topical application. TSCE creams with 100, 300, 500 mg TSCE/100 g cream were successfully developed. Antioxidant activity of TSCE cream products was evaluated by DPPH radical scavenging assay. The result showed that TSCE creams possessed high percentage of scavenging activity in comparison with vitamin C and TSCE reference.