Cytotoxic Triterpenes from a Marine Sponge, Stelletta sp.

Abstract

Bioassay-guided fractionation of an extract of a marine sponge, Stelletta sp., has led to the isolation and characterization of four new cytotoxic isomalabaricane triterpenes, named stellettins C (1), D (2), E (3), and F (4). Three known triterpenes (5-7) were also isolated from the same extract. The most sensitive of the tested cell lines (e.g., leukemia, central nervous system, renal) generally responded with GI50 concentrations in the low-to-mid nanomolar range.

Bioactive Isomalabaricane Triterpenes from the Marine Sponge Rhabdastrella globostellata

“…The chemical shift of H-3 (δ 4.55, m) indicated the equatorial ( ) position of the acetoxy function. [5][6][7]11 This stereochemistry was confirmed by NOE correlations between H-3/H-5 and H-3/H 3 -28. Additional COSY couplings between H 2 -1/H 2 -2, H-5/H 2 -6, H 2 -6/H 2 -7, and H-9/H 2 -11 together with the corresponding HMBC correlations (Table 1) allowed the assemblage of the tricyclic nucleus.…”

“…The specimen from Northern Australia reported as Jaspis sp. 6 was reexamined by one of us (J.N.A.H.) and is also R. globostellata.…”

Triterpenoids as Anticancer Drugs from Marine Sponges

“…Since then, they have been isolated from several genera of marine sponges belonging to the order Astrophorida including members of the genera Rhabdastrella, Stelletta, Jaspis, and Geodia [13] The cytotoxic isomalabaricane-type triterpenoids stellettins A-K (1-13) have been reported from the marine sponge species of the genus Jaspis [14], Stelleta [15][16][17], and Rhabdastrella [18]. Stellettin A (1) and B (2), were isolated from the sponge Stelletta tmuis collected from Hainan Island, China in 1994.…”

“…Stelletin C (3) and D (4) were the most potent derivative with a mean panel GI 50 of 0.09 µM. The stelletin E (5) and F (6) pair was approximately 10-times less potent (mean GI 50 of 0.98 µM) [13,15].…”

Structural analogues of schweinfurthin F: Probing the steric, electronic, and hydrophobic properties of the D-ring substructure

“…7 Importantly, the schweinfurthins show no correlation to any clinically used anti-neoplastic agent, indicating that this family of compounds may act via a novel mechanism or target. 8 Only three structurally unrelated families of natural products show any appreciable correlation to the schweinfurthins: the cephalostatins, 9 the stellettins, 10 and OSW-1. 11 Presumably, a determination of the molecular target of one of these compounds would aid in a similar determination with the others, thus increasing understanding of their biological activity.…”