Antioxidant and cytoprptective effects of Tamarindus indica seed coat extract

Abstract

This study aimed to determine antioxidant activities of Tamarindus indica seed coat extracts and evaluate its protective activities against hydrogen peroxide (H2O2)-induced oxidative stress in human foreskin fibroblast CCD-1064Sk cells. The roasted seed coat of tamarind was extracted with various solvent systems: 70% ethanol (TSCE-E), ethyl acetate (TSCE-EA), 70% ethanol followed by partition with chloroform and then ethyl acetate (TSCE-EEA), and boiling-water followed by partition with ethyl acetate (TSCE-W). The highest phenolic content was observed in TSCE-W which revealed the free radical scavenging activities in cell-free system. TSCE-W possessed the highest DPPH● and ABTS●+ scavenging activities. TSCE-W was also exhibited superoxide anion radical, hydroxyl radical, H2O2, and nitric oxide scavenging activities, including reducing power and anti-lipid peroxidation activities comparable with other TSCEs. In cell-based assay, TSCE-W up to 1 mg/mL did not show cytoxicity against CCD-1064Sk cells as determined by various standard assays: MTT, neutral red, Hoechst 33342 staining and trypan blue dye exclusion assay. Cells treated with TSCE-W alone at the non-toxic concentration did not generate reactive oxygen species (ROS) and lipid peroxidation. Additionally, TSCE-W significantly increased intracellular glutathione (GSH) level and the activity of superoxide dismutase (SOD) and catalase (CAT). TSCE-W reduced the generation of ROS and lipid peroxidation as well as increased intracellular GSH level in H2O2-treated cells. The antioxidant mechanism of TSCE-W via protein expression was performed using Western blot analysis. The result showed that treatment of TSCE-W before H2O2 exposure for 3 h significantly up-regulated the protein expression of antioxidant enzymes including copper, zinc superoxide dismutase (Cu,ZnSOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) as compared with vehicle control. Treatment of TSCE-W prior to H2O2 exposure for 6 h maintained the protein expression of Cu,ZnSOD, GPx, and CAT comparable with vehicle control. The results suggest that an inexpensive and simple boiling-water extraction of TSCE-W may provide a good source of natural antioxidant. TSCE-W protected oxidative stress in cells by the regulation of antioxidant enzymes expression, TSCE-W potentially useful for health food additives and cosmeceuticals.