Bioactive steroidal glycosides from the marine sponge Erylus lendenfeldi

Bioassay-guided fractionation of the methanol extract of Erylus lendenfeldi using engineered strains of budding yeast (Saccharomyces cerevisiae) has resulted in the isolation of the known compound eryloside A () and two new compounds, erylosides K () and L (). The structures were established based mainly on 1D and 2D NMR data. The absolute stereochemistry of eryloside A, which had never been fully characterized, was determined using the modified Mosherʹs method. The absolute stereochemistry of eryloside K was determined by comparison with tetrahydroeryloside A. Compounds exhibited selective cytotoxicity against a yeast strain (Δrad50) deficient in double strand break (DSB) repair.