New steroidal saponins from the sponge Erylus lendenfeldi

Fouad, Mostafa and Al-Trabeen, Khaled and Badran, Mohammad and Wray, Victor and Edrada-Ebel, Ruangelie and Proksch, Peter and Ebel, Rainer (2004) New steroidal saponins from the sponge Erylus lendenfeldi. Arkivoc, 2004 (13). pp. 17-27. ISSN 1551-7004

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Our search for biologically active marine natural products has led to the isolation of two new steroidal saponins, eryloside K (2) and eryloside L (3) together with the known antitumor and antifungal glycoside eryloside A (1) from the organic extract of the sponge Erylus lendenfeldi (Geodiidae) collected in the Red Sea. The structures of the new compounds were elucidated on the basis of comprehensive spectral analyses ( 1H, 13C, COSY, HMQC, HMBC and TOCSY NMR) as well as GC/MS analysis to infer the absolute stereochemistry of the sugar moieties. Eryloside K (2) is the 24,25-didehydro congener of 1, while eryloside L (3) features an unusual 8α,9α- epoxy-4α-methyl-8,9-secocholesta-7,9(11),14-triene skeleton which appears to be unprecedented in nature. Eryloside A (1) displayed antibacterial activity against Bacillus subtilis and Escherichia coli together with antifungal activity against Candida albicans.