Cytotoxic activity of Ocimum tenuiflorum crude extracts against an A375 malignant melanoma cell line

Abstract

Malignant melanoma is a rare skin cancer that transpires in the melanocytes. This is often caused by constant ultraviolet (UV) exposure, which results in genetic mutations leading to carcinogenesis. When left untreated, malignant melanoma may lead to death due to its high metastatic potential, it is therefore regarded as the most dangerous form of skin cancer. Existing cancer treatments, despite their advancements, still have several limitations that impact their effectiveness and applicability, thus prompting the exploration of alternative therapeutic options. Medicinal plants, employed for centuries and embraced by 70 % of the population in developing nations, present a potential avenue for novel treatments. Thus, this study aimed to investigate the potential use of four Ocimum tenuiflorum solvent extracts in treating malignant melanoma. Sequential extraction of O. tenuiflorum was performed to obtain four crude extracts (hexane, dichloromethane, methanolic and ethyl acetate). These extracts were evaluated against the A375 cell line to determine apoptotic induction, with the mode of cell death confirmed flow cytometry. Gas Chromatography-Mass Spectrometry (GC/MS) profiling was performed to identify the possible bioactive constituents of each extract. Screening of the four extracts revealed significant cytotoxic potential against A375 cells, with calculated IC₅₀ values <50 µg/mL. Microscopic analyses unveiled morphological alterations indicative of apoptosis, including cell blebbing, reduced cell size, nuclear fragmentation and potential chromatin condensation. Flow cytometric analysis confirmed that 44.2 ± 2.54 %, 73.6 ± 1.13 % and 67.4 ± 0.70 % of A375 cells underwent late apoptosis induced by the hexane, dichloromethane and ethyl acetate crude extracts respectively. GC/MS metabolite profiling of the ethyl acetate extract using the Shimadzu 2010 QB gas chromatograph revealed the presence of palmitic acid, methyl palmitate, stearic acid, myristic acid and linolenic acid as potential bioactive compounds. The findings from this study thus underscore the anti-cancer properties of O. tenuiflorum crude extracts, demonstrating their efficacy in inducing cytotoxicity in malignant melanoma A375 cells. These in vitro results present promising implications for developing anti-cancer therapies targeting the A375 cell line.