Cytoprotective and wound healing effects of Tamarindus Indica seed coat extracts on human cell lines

Abstract

Tamarind seed-coats have long been used in traditional medicine for treatment of burn and chronic wound in diabetic patients. Phenolic compounds in tamarind seed-coat extract have also widely studied for antioxidant activity. This study was designed to evaluate the cytoprotective and wound healing effect of phenolic compounds in the tamarind seed-coat extracts (TSCEs) from the three tamarind cultivars including sweet and sour tamarinds against hydrogen peroxide (H₂O₂)-induced oxidative injury in two human cell lines. Tamarind seed-coat was extracted with boiling water (fraction1) and then the water extract was partitioned with an equal volume of ethyl acetate (fraction 2) and the seed-coat residues were re-extracted with 70% acetone (fraction 3). Three fractions of tamarind seed-coat extracts were dried, the total phenolic contents were analyzed and cytotoxic effect was evaluated on human foreskin fibroblasts (CCD-1064Sk) and human gastric adenocarcinoma epithelial cells (AGS) by MTT and DNA stain assays. The three fractions of tamarind seed-coat extracts composed of various amount of phenolic contents and the ethyl acetate fraction (fraction 2) exhibited the lowest cytotoxic effect in both of the human cells tested. The ethyl acetate fraction (fraction 2) of the tamarind seed-coat extracts (TSCEs) from the three tamarind cultivars were used to evaluated for their cytoprotective and wound healing effects. The phenolic compounds in the sour tamarinds composed of tannin and procyanidin which were higher than the sweet tamarind. The chromatogram of HPLC profile of TSCEs from the three tamarind cultivars showed the peaks that identical with the three standard flavonoids including (+)-catechin, procyanidin B2 and (-)-epicatechin. The cytoprotective effect of TSCEs from the three tamarind cultivars was evaluated by NRU and DCFH-DA assays. The TSCEs exhibited cytoprotective effect by decreasing the number of damaged cells and reducing the intracellular ROS generations against H2O2-induced cells damage in both human cells tested. At the lower concentrations of the three TSCEs were used to evaluate the proliferative effect on the tested human cells by using NRU assay. Wound healing effect of TSCEs at the proliferative concentrations was evaluated by using the scratch assay, TSCEs did not show wound healing effect on both of the treated human cells. However, TSCEs exhibited cytoprotective effect on H₂O₂-induced oxidative stress in the scratch wound of CCD-1064Sk and AGS cells. TSCEs increased the rate of wound closure against H₂O₂–induced the delayed rate of wound closure. The lower concentrations of TSCEs from the sweet tamarind accelerated the rate of wound repair in CCD-1064Sk cells better than H₂O₂–treated cells (untreated with TSCEs), which was due to the scavenging effect of the TSCE against ROS-caused the delay of wound closure. The TSCEs of the sour tamarinds possessed the ROS scavenging effect in AGS cells, a better acceleration the percent wound closure than their H₂O₂-treated cells (untreated with TSCEs) was observed.