Isolation and characterization of new secondary metabolites from Asphodelus microcarpus

Phytochemical study of the ethanolic extract of Asphodelus microcarpus Salzm. et Viv. (Asphodelaceae) resulted in the isolation of two new compounds, methyl-1,4,5-trihydroxy-7-methyl-9,10-dioxo-9,10-dihydroanthracene-2-carboxylate (1), and (1R) 3,10-dimethoxy-5-methyl-1H-1,4-epoxybenzo[h]isochromene (2) as well as three known compounds; 3,4-dihydroxy-methyl benzoate (3), 3,4-dihydroxybenzoic acid (4), and 6-methoxychrysophanol (5). Compound 1 showed a potent activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus with IC50 values of 1.5 and 1.2 μg/mL, respectively. Compound 3 showed antileishmanial activity with an IC50 value of 33.2 μg/mL. Compound 2 is the first isochromene possessing a highly strained 1,4-epoxy moiety. The structure elucidation of isolated metabolites was carried out using spectroscopic data, the absolute configuration of 2 based on optical rotation and electronic circular dichroism experiments and calculations.