Discovering new bioactive molecules from endolichenic fungi, Curvularia trifolii and Penicillium Citrinum

Abstract

Endolichenic fungi are microorganisms living in the thalli of lichens that are analogous to the plant endophytic species inhabiting the intercellular spaces of the hosts. The diversity and prevalence of endolichenic fungi have not been studied extensively and there are only a few recorded studies on isolations and identifications of endolichenic fungi. The endolichenic fungi available in Sri Lanka are still an untapped source of bioactive natural products since their identity and the chemistry of their secondary metabolites have not been explored thoroughly. In our ongoing research programme on searching for new bioactive compounds from endolichenic fungi, we have investigated an endolichenic fungi, Curvularia trifolii and Penicillium citrinum isolated from the lichens, Usnea sp. and Parmotreama sp. collected in the Hakgala Botanical Garden, Sri Lanka. Ethyl acetate extracts of two endolichenic fungi, C. trifolii and P. citrinum led to isolation of four new compounds, 1- 4. The structures of the new compounds were determined on the basis of their 1D NMR, 2D NMR and FABMS spectroscopic data. The new compounds, 1 - 4 showed radical scavenging activities with IC50 values of 4.0±2.6 mg/mL, 1.3±0.2 mg/mL, 159.7±22.3 μg/mL and 68.6±4.3 μg/mL respectively in DPPH antioxidant assay and antioxidant activity of the compound 2 was comparable to the standard antioxidant compound, BHT. Moreover, the new compound, 2 were evaluated for their antiinflammatory activity and exhibited significant activity comparable to the standard antiinflammatory drug, Aspirin. The Compound 1 was evaluated for inhibition of cell proliferation in a panel of five cancer cell lines NCI-H460, MCF-7, SF-268, PC-3M, and MIA Pa Ca-2 and exhibited >90% inhibitory activity at 5 μg/mL with all the above cell lines.