Abstract
Four new eunicellin-type hirsutalins S–V (1–4), along with a known compound (–)-6α-hydroxy polyanthellin A (5), were isolated from the soft coral Cladiella hirsuta. The structures of the metabolites were determined by extensive spectroscopic analysis. Cytotoxity of compounds 1–5 against the proliferation of a limited panel of cancer cell lines was measured. Anti-inflammatory activity of compounds 1–5 was evaluated by measuring their ability in suppressing superoxide anion generation and elastase release in fMLP/CB-induced human neutrophils.
Highlights
This was confirmed by the downfield shift of C-3 of hirsutalin A, relative to that of 2, and the HMBC connectivity from H-4 (δ 5.08) to the carbonyl carbon resonating at δ171.2 (C) (Table 1)
By comparison of the NMR data of with those of hirsutalin C [29], it was found that a C-7/C-16 double bond in hirsutalin C was replaced by an oxymethine bearing a methyl and a hydroxy group in 4, as confirmed by HMBC correlations observed from H3-16 (δ 1.25, 3H, s) to C-6 (δ 80.6, CH), C-7 (δ 77.0, C) and C-8 (δ 45.5, CH2)
The animal Cladiella hirsuta was collected by hand using SCUBA off the coast of Sianglu Islet
Summary
The chemical investigations on soft corals of the genus Cladiella and Klyxum [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32] have afforded series of eunicellin-based diterpenoids, of which many have been shown to exhibit attracting biological activities [8,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]. We have previously isolated some bioactive eunicellins and steroids from a Taiwanese soft coral Cladiella hirsuta. Our recent studies of C. hirsuta have led to the discovery of 18 eunicellin-based diterpenoids, hirsutalins A–R [29,30,31], some of which have been found to possess cytotoxic [29,31] and anti-inflammatory activities [29,30,31]. We further report the isolation of four new eunicellin-based compounds, hirsutalins S–V along with a known compound (–)-6α-hydroxy polyanthellin A (5) [32] from C. hirsuta (Chart 1). The structures of new compounds were determined by extensive spectroscopic analysis.
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