Mycalosides B−I, Eight New Spermostatic Steroid Oligoglycosides from the Sponge Mycale laxissima

Abstract

New steroidal oligoglycosides mycalosides B-I (2-9) have been isolated from the polar extract of the Caribbean sponge Mycale laxissima, and their structures have been elucidated by 1D and 2D NMR ((1)H, (13)C, DEPT, COSY-45, COSY-RCT, HSQC, HMBC, and NOESY spectra) and MALDI-TOF mass spectrometry. Mycalosides B (2) and C (3) were shown to be 27- and 28-nor derivatives of the previously known tetraoside mycaloside A (1). Mycaloside D (4) differs from 1 only in the presence of an additional acetyl group in the carbohydrate moiety. Mycaloside E (5) was structurally identified as a 28-nor-4-dehydroxy derivative of 1. Mycalosides F-H (6-8), differing from each other by the structures of their side chains and nonacetylated (7, 8) or acetylated (6) tetrasaccharide carbohydrate moieties, have new 5(6)-unsaturated 3 beta,4 beta,21-trihydroxy-15-keto-steroidal aglycons. Mycaloside I (9) is a tetraoside of a new 7,24(28)-diunsaturated 3beta,15 beta,29-trihydroxystigmastane aglycon. It was established that the total fraction of the mycalosides as well as mycalosides A (1) and G (7) inhibit the fertilization of eggs by sperm of the sea urchin Strongylocentrotus nudus preincubated with these compounds.

Chemical and Biological Aspects of Marine Sponges from the Family Mycalidae

“…The first two cholesterol derivatives 158 and 159 were reported from the Indian sponge M. (Carmia) mytilorum [22]. The compound 158 was also isolated together with cholesterol (160) and seven other sterols (161-167) in the free sterol fraction of a specimen of M. (Arenochalina) laxissima from Cuba [125]. Cholesterol (160) was also reported from a Chinese Mycale sp.…”

“…[93]. Two of these compounds, (+)-curcudiol (125) and (+)-curcuphenol (126), have been characterised previously. The other three isomeric structures, the C-4′ hydroxyl epimers (127) and 3′,4′-didehydrocurcudiol (128), were reported for the first time [93].…”

“…15), have been characterised from a Cuban M. (Arenochalina) laxissima [125,134,135]. The aglycones of mycalosides A-H (172-179) consist of a polyhydroxylated Δ 5 steroid, and mycaloside I (180) consists of a polyhydroxylated Δ 7 steroid [125].…”

“…The aglycones of mycalosides A-H (172-179) consist of a polyhydroxylated Δ 5 steroid, and mycaloside I (180) consists of a polyhydroxylated Δ 7 steroid [125]. Additionally, mycalosides F, G, and H (177-179) possess a ketone group at position C-15 on the sterol nucleus [125]. Steroidal and tetracyclic triterpenoid glycosides have been isolated from several sponge orders including Tetractinellida, Poecilosclerida, Axinellida, and Haplosclerida.…”

“…In addition to those isolated from the family Mycalidae, glycosides have been reported in other genera of the order Poecilosclerida, including the Ulosa [136], Pandaros [137], and Ectyoplasia [138]. Mycalosides A-I (172-180) have displayed activity as spermostatics, inhibiting the fertilisation of sea urchin (Strongylocentrotus nudus) eggs, with individual glycosides showing EC 50 values of 32 µg/mL [125]. Sponge glycosides have shown biological activities leading to the conclusion that they can serve multiple ecological roles such as feeding deterrents, prevention of biofilm formation, chemical signalling, and allelopathy (see [139] for a review of activities).…”