Abstract
Two undescribed rearranged cadinane-type sesquiterpenoids (1–2), named sinulaketol A-B, together with one new chlorinated steroid (3), one new gorgosterol (4), one known sesquiterpene (5), one known dibromoditerpene (6) and two known polyhydroxylated steroids (7–8) were isolated from the soft coral Sinularia brassica. The structures of these compounds were established by extensive spectroscopic analysis, including HRESIMS, 1D, and 2D NMR spectroscopy. Their absolute configurations were also determined by the ECD calculations and DP4+ probability analysis. Antileishmanial activity of compounds 1–8 was evaluated in vitro against the amastigote forms of Leishmania donovani, in which compounds 3, 6, and 7 inhibited the growth of L. donovani by 58.7, 74.3, 54.7%, respectively, at a concentration of 50 μM. Antimicrobial effect of the isolated compounds were also evaluated against Candida albicans, Staphylococcus aureus, and Escherichia coli. Compound 6, a brominated diterpene, exhibited antimicrobial effect against S. aureus.
Highlights
Soft corals of the genus Sinularia, which belong to the order Alcyonacea, are important sources of bioactive natural products and have been the target of study since the middle of twentieth century
Our investigation on the chemical compositions of S. brassica had led to the discovery of two undescribed rearranged cadinane-type sesquiterpenoids (1–2), one new chlorinated steroid (3), one new gorgosterol (4) (Figure 1), one known sesquiterpene
NMR experiments (HSQC, HMBC, COSY, and NOESY) and confirmed by High-resolution Electrospray Ionization mass (HRESIMS). Their absolute configurations were comprehensively established by the ECD calculations and NMR chemical shifts calculations supported by DP4+ analysis
Summary
Soft corals of the genus Sinularia, which belong to the order Alcyonacea, are important sources of bioactive natural products and have been the target of study since the middle of twentieth century. A further chemical investigation may likely discover more interesting compounds from the soft coral S. brassica. Our investigation on the chemical compositions of S. brassica had led to the discovery of two undescribed rearranged cadinane-type sesquiterpenoids (1–2), one new chlorinated steroid (3), one new gorgosterol (4) (Figure 1), one known sesquiterpene (5), one known dibromoditerpene (6) and two known polyhydroxylated steroids (7–8). The structures of these compounds were established by spectrometric and spectroscopic approaches, quantum mechanics-based chemical shifts calculation with support of the.
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