In vitro screening of cytotoxic, antimicrobial and antioxidant activities of Clinacanthus nutans (Acanthaceae) leaf extracts

Abstract

Purpose: To evaluate the in vitro cytotoxic, antioxidant and antimicrobial activities of Clinacanthus nutans extracts and semi-fractions. Method: The plant was subjected to cold solvent extraction to produce petroleum ether, ethyl acetate and methanol crude extracts, followed by isolation using bioassay-guided fractionation. The crude extracts (0.2 to 10.0 mg/ml) were tested against HeLa and K-562 cell lines using 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and antioxidant activity using 1, 1-diphenyl-2- picrylhydrazyl (DPPH) assay. Furthermore, fractions isolated from ethyl acetate leaf extract (0.02 to 10.0 mg/ml) were tested against Bacillus cereus (ATCC11778), Escherichia coli (ATCC25922), Salmonella enterica Typhimurium (ATCC14028) and Candida albicans (ATCC10231) using minimum inhibitory concentration (MIC) and minimum bactericidal or fungicidal (MBC/MFC) assays. Results: Petroleum ether extracts demonstrated the strongest cytotoxic activity against HeLa and K- 562 cells with IC50 of 18.0 and 20.0 μg/mL, respectively. Petroleum ether extracts also displayed the highest radical scavenging activity of 82.00 ± 0.02%, compared with ascorbic acid and α-tocopherol corresponding values of 88.7 ± 0.0 and 86.6 ± 0.0%, respectively. In MIC assay, all the crude extracts and fractions showed inhibition against all tested microorganisms. Fraction 7 displayed the lowest MIC and MBC/MFC values against B. cereus and C. albicans at 1.39 mg/ml, respectively. Ampicillin and amphotericin B displayed MIC value of 1.3 mg/ml. Conclusion: The bioactive compounds from C. nutans are potential cytotoxic, antimicrobial and antioxidant agents.