Abstract
Five new cembranoid-related diterpenoids, namely, flexibilisins D and E (1 and 2), secoflexibilisolides A and B (3 and 4), and flexibilisolide H (5), along with nine known compounds (6–14), were isolated from the soft coral Sinularia flexibilis. Their structures were established by extensive spectral analysis. Compound 3 possesses an unusual skeleton that could be biogenetically derived from cembranoids. The cytotoxicity and anti-inflammatory activities of the isolates were investigated, and the results showed that dehydrosinulariolide (7) and 11-epi-sinulariolide acetate (8) exhibited cytotoxicity toward a limited panel of cancer cell lines and 14-deoxycrassin (9) displayed anti-inflammatory activity by inhibition of superoxide anion generation and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLF/CB)-induced human neutrophils.
Highlights
Soft corals have been known to be the organisms possessing secondary metabolites with high diversity in chemical structures [1]
2 is a 12-hydroxy-11-oxo derivative of 1. This was supported by the correlations spectroscopy (COSY) and heteronuclear multiple bond correlation (HMBC) correlations structure and absolute configurations of the stereogenic centers of 2 were confirmed by an alkaline (Figure 3)
The results revealed that, at a concentration of 10 μM, 9 exhibited significant inhibition toward superoxide anion generation and elastase release with IC50 values of 10.8 ± 0.38 and 11.0 ± 1.52 μM, respectively
Summary
Soft corals have been known to be the organisms possessing secondary metabolites with high diversity in chemical structures [1]. 2 is a 12-hydroxy-11-oxo derivative of 1 This was supported by the COSY and HMBC correlations structure and absolute configurations of the stereogenic centers of 2 were confirmed by an alkaline (Figure 3). The relative configurations of C-11 and C-15 were determined by a combination of NOESY correlations (Figure 5) and pyridine-induced solvent shift experiment [31]. The 13 C NMR data of 4 (Table 3) showed signals attributable to two double bonds (δc 139.5, 126.0, 136.9, 124.1), one ketone carbonyl (δc 205.6), and. The 13C NMR data of 4 (Table 3) showed signals attributable to two double bonds (δc 139.5, 126.0, 136.9, 124.1), one ketone carbonyl (δc 205.6), and two ester carbonyls (δc 175.4, 165.3), which accounted for five degrees of unsaturation.
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