Abstract

This study aims to investigate the cytotoxicity of Andrographis paniculata, Ziziphus spina-christi and Gymnanthemum extensum crude extracts and their combination with low piperine fractional Piper nigrum extract. All plants were extracted with water and five organic solvents (methanol, ethanol, dichloromethane, ethyl acetate and hexane). Cytotoxicity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay on three cancer types (breast, colorectal and ovarian cancers) and two non-cancerous cells. The combination among extracts with low piperine fractional Piper nigrum extract was separately conducted in several tests including cytotoxicity, apoptosis and multi caspase activity. We found that, the dichloromethane crude extract of Andrographis paniculata, Ziziphus spina-christi and Gymnanthemum extensum exhibited the strongest cytotoxicity on colorectal cancer cells SW-620 (7.49±0.04 µg. ml^-1), breast cancer cells Michigan Cancer Foundation-7 (13.35±0.30 µg. ml^-1) and ovarian cancer cells A2780 (15.58±1.81 µg. ml^-1), respectively. Gas chromatography mass spectrometry study of dichloromethane crude extract of Andrographis paniculata, Ziziphus spina-christi and Gymnanthemum extensum identified major compounds including 1-heptatriacotanol (60.29 %) and palmitic acid (26.92 % for dichloromethane crude extract of Ziziphus spina-christi and 21.40 % for dichloromethane crude extract of Gymnanthemum extensum), respectively. The combination of dichloromethane crude extract of Ziziphus spina-christi and low piperine fractional Piper nigrum extract at ratio IC₅₀:0.5IC₅₀ showed a moderate synergistic effect on Michigan Cancer Foundation-7 cells. Interestingly, the mixture of dichloromethane crude extract of Gymnanthemum extensum with low piperine fractional Piper nigrum extract at ratio IC₅₀:IC₅₀, 0.5 IC₅₀:IC₅₀ and IC₅₀:0.5 IC₅₀ exhibited a synergistic effect on Michigan Cancer Foundation-7 cells. Moreover, combination of dichloromethane crude extract of Gymnanthemum extensum with low piperine fractional Piper nigrum extract induced the apoptosis and multi caspase activity in a time dependent manner. In conclusion, dichloromethane crude extract of Andrographis paniculata, Ziziphus spina-christi and Gymnanthemum extensum displayed potent anticancer activities and the combination of dichloromethane crude extract of Gymnanthemum extensum with low piperine fractional Piper nigrum extract can be a promising regimen for an alternative cancer treatment