Anticancer Activity Evaluation

Anticancer screening of herbal extracts most commonly employs the MTT (or the analogous SRB) cytotoxicity assay against a panel of human cancer cell lines, including MCF-7 (breast), A549 (lung), HeLa (cervical), HCT-116 (colon), and HepG2 (liver), following the same seeding, treatment, and colourimetric endpoint protocol described for synthetic compound screening. Because a herbal extract's cytotoxicity must be interpreted in light of its selectivity for malignant over normal cells, reviewers and regulators expect the calculation of a Selectivity Index (SI), defined as the IC50 against normal cells divided by the IC50 against the cancer cell line under study, with an SI greater than approximately three generally regarded as indicating an acceptable safety margin for further development. Beyond simple cytotoxicity, a credible herbal anticancer study is expected to include at least one mechanistic assay addressing the mode of cell death — commonly Annexin V/propidium iodide flow cytometry to distinguish apoptosis from necrosis, cell-cycle analysis by propidium iodide staining and flow cytometry, or reactive oxygen species generation assay — together with a direct comparison against a standard chemotherapeutic reference such as doxorubicin, paclitaxel, or 5-fluorouracil.