Antioxidant activities of thermally treated Sesamum indicum L. leaf extracts and their inhibitory effects against growth and metastatic properties of human colon cancer cells

Abstract

The study aimed to investigate antioxidant activities of two different thermally treated sesame (Sesamum indicum L.) leaf ethanol extract, steamed sesame leaf extract (SSLE) and roasted sesame leaf extract (RSLE), and their inhibitory effects on uncontrolled growth and increased metastatic properties in human colon cancer cell lines. Both SSLE and RSLE contained pedaliin as the major polyphenol and its aglycon, pedalitin, as a minor component and exhibited radical scavenging activities and ferric reducing antioxidant power. SSLE and RSLE decreased growth of HT29 and HCT116 colon cancer cells, which was attributed to the induction of apoptosis and cell cycle arrest at either G2/M (by SSLE in HCT116) or S phase (by RSLE in HCT116). Furthermore, SSLE and RSLE inhibited migration and adhesion in both cell lines. These results indicate that thermally treated sesame leaves retained pedaliin content and exhibited antioxidant activities and inhibitory activities against the growth and metastatic properties of colon cancer cells.

Keywords: Antioxidant activity; Colon cancer cell; Pedaliin; Sesame leaf extract; Thermal treatment.

Fig. 1

The HPLC chromatograms of SSLE and RSLE. Representative chromatogram of pedaliin standard, pedalitin standard, SSLE, RSLE, and raw SLE were shown

Fig. 2

Antioxidant activities of SSLE and RSLE. Two different radical scavenging activities (DPPH, and ABTS) and ferric reducing antioxidant power (FRAP) of SSLE and RSLE are expressed as a percentage (DPPH at 250 μg/mL, ABTS at 500 μg/mL, FRAP at 50–500 μg/mL). Significant differences between SSLE and RSLE are indicated by asterisks (***p < 0.001). Significant differences among concentrations within each treatment of SSLE and RSLE are denoted by different letters (a–d) (p < 0.05)

Fig. 3

Effects of SSLE and RSLE on cell growth in human colon cancer cells. HT29 (A) and HCT116 cells (B) were treated with SSLE and RSLE at concentrations ranging from 0 to 500 μg/mL for 24 h, 48 h, and 72 h. The percentage of viable cells were determined relative to the control. Significant differences among concentrations within each treatment group (SSLE and RSLE) are denoted by different letters (a–e) (p < 0.05). Significant differences between SSLE- and RSLE-treated groups at each concentration are indicated by asterisks (*p < 0.05, **p < 0.01, ***p < 0.001)

Fig. 4

Effects of SSLE and RSLE on cell cycle distribution in human colon cancer cells. HT29 (A) and HCT116 cells (B) were treated with either 0 (control, CTRL) or 500 μg/mL of SSLE and RSLE for 72 h. The percentage of cell population in sub-G1 (M4, apoptotic), G0/G1 (M1), S (M3), and G2/M (M2) phases were determined by flow cytometry. Significant differences among groups in each phase are denoted by different letters (a–c) (p < 0.05). NS denotes non- significant difference

Fig. 5

Effects of SSLE and RSLE on migration and adhesion in human colon cancer cells. In scratch wound healing assay, HT29 and HCT116 cells were treated with SSLE and RSLE at respective concentration (50 μg/mL for HT29, 100 μg/mL for HCT116, and control, CTRL) for 24 h, and the percentage of migratory cells was determined by measuring wound closure relative to the control (A). In adhesion assay, HT29 and HCT116 cells were treated with SSLE and RSLE at an indicated concentration (0, 250, or 500 μg/mL) for 1 h, and the percentage of adherent cells was determined relative to the control (B). Significant differences among groups are denoted by different letters (a–c) (p < 0.05). Significant differences between SSLE- and RSLE-treated groups at each concentration are indicated by asterisks (***p < 0.001)