Maria Carmen S. Tan1, Glenn G Oyong2, Chien-Chang Shen3, Consolacion Y Ragasa4
1Department of Chemistry, De La Salle University, Manila 1004, Philippines.
2Department of Biology, De La Salle University; Center for Natural Science and Environmental Research, De la Salle University, Manila 1004, Philippines.
3Division of Chinese Medicinal Chemistry, National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei, Taiwan.
4Department of Chemistry, De La Salle University, Manila 1004; Department of Chemistry, De La Salle University Science and Technology Complex Leandro V. Locsin Campus, Biñan City, Laguna 4024, Philippines.
Introduction: Although diterpenes from Andrographis paniculata Burm.f. Nees have been found to have chemotherapeutic activity, a thorough investigation on the cytotoxic and anti-proliferative analyses on different cancer cell lines using these isolated constituents has not been achieved. Objectives: The primary objective of this study was to probe the cytotoxic capacity of the labdane diterpenoids andrographolide (1), 14-deoxyandrographolide (2), 14-deoxy-12-hydroxyandrographolide (3), and neoandrographolide (4) on mutant and wild type immortalized cell lines. Methods: Breast adenocarcinoma (MCF-7), colon carcinomas (HCT-116 and HT-29), small cell lung carcinoma (H69PR), human acute monocytic leukemia (THP-1), and wild type primary normal human dermal fibroblasts – neonatal cells (HDFn) were incubated with 1-4 and the degree of cytotoxicity was analyzed by employing the in vitro PrestoBlue® cell viability assay. Working solutions of 1-4 were prepared in complete cell culture medium to a final non-toxic DMSO concentration of 0.2%. The plates were incubated at 37°C with 5% CO2 in a 98% humidified incubator throughout the assay. Nonlinear regression and statistical analyses were done to extrapolate the half maximal inhibitory concentration, IC50. One-way ANOVA (P < 0.05) and multiple comparison, Tukey’s post hoc test (P < 0.05), was used to compare different pairs of data sets. Results were considered significant at P < 0.05. Results: The highest cytotoxicity index was exhibited by the H69PR and 1 trials which displayed the lowest IC50 value of 3.66 μg/mL, followed by HT-29 treated with 2, HCT-116 and 1 trials, and H69PR treated with 4 (IC50 = 3.81, 3.82 and 4.19 μg/mL, respectively). Only 1 and 4 were detrimental towards MCF-7; while 1, 3, and 4 were degenerative against H69PR. Tukey’s post hoc multiple comparison indicated no significant difference in the cytotoxicity of 1-4 on HCT-116 cells which afforded IC50 values ranging from 3.82 to 5.12 μg/mL. Evaluation of the two colon carcinoma cell lines showed that HCT-116 was categorically more susceptible to cellular damage caused by treatments with 1-4 than was HT-29. Cytotoxicity was not detected in THP-1 and HDFn cells (IC50 >100 μg/mL). Conclusion: Diterpenoids 1-4 isolated from the dichloromethane extract of the leaves of A. paniculata exhibited different cytotoxic activities against MCF-7, HCT-116, HT-29, H69PR. All constituents had comparable action on HCT-116 cells but were not found to be cytotoxic to normal HDFn cells and mutant THP-1 cells.
Keywords: Andrographis paniculata (Burm. f.) Nees, Cytotoxicity, PrestoBlue cell viability assay.