In-vitro ANTICANCER ACTIVITY OF LICHEN Heterodermia boryi AND ITS SECONDARY METABOLITES

Abstract

Lichens are symbiotic organisms that have been traditionally used for treating different kinds of ailments. Heterodermia boryi is a common foliose lichen found growing luxuriantly in the Western Ghats. It is clear from the literature survey that there are no reports on the isolation and biological activity of lichen substances from Heterodermia boryi, we thought of exploring the anticancer activity of its crude extract and isolated compounds. Fractionation of crude methanolic extract of Heterodermia boryi by column chromatography led to the isolation of three pure compounds. The crude methanolic extract and isolated compounds were screened for in vitro cytotoxic activity against three different human cancer cell lines such as breast (MCF-7), lung (H1975), and colon (HCT-116). Isolated compounds with the highest activity were further evaluated for their ability to induce apoptosis by dual staining method on the MCF-7 cell line. Molecular docking studies were carried out to study the ability of isolated compounds to interact with Mitogen-activated protein kinases- 2 (Mnk2). The isolated compounds were characterized as methyl haematommate (HKB-1), atraric acid (HKB-4), and zeorin (HKB-6) by spectral methods. Among the isolated compounds, HKB-1 and HKB-6 exhibited superior IC50 values of 11.1 µg/ml and 17.02 µg/ml respectively. Dual staining of MCF-7 cells treated with HKB-1 and HKB-6 at 10 µg/ml displayed early signs of apoptosis. Molecular docking studies revealed excellent binding affinity and interaction of HKB-1 with the binding site residues of Mnk2 and were comparable with that of the co-crystallized ligand staurosporine indicative of their possible role as Mnk2 inhibitors.