Briarenols Q–T: Briaranes from A Cultured Octocoral Briareum stechei (Kükenthal, 1908)

Abstract

Our continuous chemical study of a cultured octocoral Briareum stechei led to the isolation of four new briarane diterpenoids, briarenols Q–T (1–4). The structures of new metabolites 1–4 were established by spectroscopic methods, and compounds 3 and 4 were found to inhibit the generation of inducible nitric oxide synthase (iNOS) from RAW 264.7 stimulated by lipopolysaccharides (LPS).

Briarane-Related Diterpenoids from Octocoral Briareum stechei

“…According to the above and comparing the NMR data of 3 with those of the literature, the structure of 3 was highly similar to a known briarane, briarenol R (4) (Figure 1), which was originally isolated from a cultured B. stechei [16] and was also obtained in this study, except for a hydroxy group in 3 instead of an acetoxy group at C-2 in 4. The HMBC and COSY correlations, as shown in Figure 3a The stereochemical evaluation of 2 was approached using a nuclear Overhauser effect spectroscopy (NOESY) experiment.…”

“…According to the above and comparing the NMR data of 3 with those of the literature, the structure of 3 was highly similar to a known briarane, briarenol R (4) (Figure 1), which was originally isolated from a cultured B. stechei [16] and was also obtained in this study, except for a hydroxy group in 3 instead of an acetoxy group at C-2 in 4. The HMBC and COSY correlations, as shown in Figure 3a The (+)-ESIMS mass spectra of 4 showed a pair of peaks at m/z 519/521 ([M + Na] + /[M + 2 + Na] + ) (3:1) with a relative intensity suggestive of a chlorine atom, indicating that the molecular formula of 4 was C 24 H 29 ClO 9 .…”

“…Briastecholide C (3) was isolated as an amorphous powder that showed sodium adduct ions at m/z 477.1284 and 479.1253 According to the above and comparing the NMR data of 3 with those of the literature, the structure of 3 was highly similar to a known briarane, briarenol R (4) (Figure 1), which was originally isolated from a cultured B. stechei [16] and was also obtained in this study, except for a hydroxy group in 3 instead of an acetoxy group at C-2 in 4. The HMBC and COSY correlations, as shown in Figure 3a The 13 C NMR signal of a methine unit at δC 56.3 (CH-6) was more shielded than would be expected for an oxygenated C-atom.…”

“…In our continuing research on natural substances from the marine invertebrates originally distributed in the tropical Indo-Pacific Ocean, two samples of the octocoral Briareum stechei were collected from two positions surrounded by the Kuroshio current for their interesting chemical constituents. We report on a known polyoxygenated briarane, briaexcavatolide P (1) [15], from a Formosan B. stechei, and three chlorinated briaranes, including two new metabolites, briastecholides B (2) and C (3), as well as a known analogue, briarenol R (4) [16] (Figure 1), from an Okinawan B. stechei. Isolates 1-4 were evaluated for their anti-inflammatory activity using the inhibition of inducible nitric oxide synthase (iNOS) in an in vitro pro-inflammatory model.…”

Briarenols W–Z: Chlorine-Containing Polyoxygenated Briaranes from Octocoral Briareum stechei (Kükenthal, 1908)

“…Since briarein A, a 3,8-cyclized cembranoid (briarane), was first reported from a Caribbean octocoral Briareum asbestinum (Pallas, 1766) in 1977 [1], hundreds of marine origin briarane diterpenoids with novel structures and extensive bioactivities have been obtained from various octocorals [2,3], of which octocorals belonging to the genus Briareum have been recognized as the most important source of briarane-type natural products [3]. In our previous studies, a series of interesting briarane-type diterpenoids, including briarenols A-T [4][5][6][7][8][9][10][11][12], were isolated from various octocorals belonging to the genera Briareum, Junceella, and Ellisella, collected off the waters of Taiwan, and an anti-inflammatory assay was employed to evaluate the activities of these compounds in reducing the release of inducible natural products [3]. In our previous studies, a series of interesting briarane-type diterpenoids, including briarenols A-T [4][5][6][7][8][9][10][11][12], were isolated from various octocorals belonging to the genera Briareum, Junceella, and Ellisella, collected off the waters of Taiwan, and an anti-inflammatory assay was employed to evaluate the activities of these compounds in reducing the release of inducible oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in an in vitro pro-inflammatory macrophage culture model.…”