Two New Cembranoids from the Chinese Soft Coral Sarcophyton boettgeri.

Two new cembranoids, namely sarcoboettgerols D and E, together with four known related ones, have been isolated from the soft coral Sarcophyton boettgeri collected from Weizhou Island in the South China Sea. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis, quantum mechanical nuclear magnetic resonance methods, time-dependent density functional theory-electronic circular dichroism calculations, as well as comparison with the reported data in the literature. A plausible biogenetic relationship of four cembranoids was proposed. In bioassays, sarcomililatin B exhibited cytotoxic activity against H1299 cell (IC50 =35.0 µM), whereas sarcomililatin B and sarcomililatin A displayed moderate antibacterial activities (MIC 17.4-34.8 µg/mL).

Chemistry, Chemo-Ecology, and Biological Activities of Uncommon and Structurally Diverse Sesquiterpenoids from the Sanya Bay Nudibranch Hexabranchus sanguineus.

A detailed chemical investigation of the Sanya Bay nudibranch Hexabranchus sanguineus yielded thirteen new sesquiterpenoids, namely sanyagunins A-H, sanyalides A-C, and sanyalactams A and B, along with eleven known related ones. Sanyalactams A and B feature an unprecedented hexahydrospiro[indene-2,3'-pyrrolidine] core. The structures of new compounds were established by a combination of extensive spectroscopic data analysis, quantum mechanical-nuclear magnetic resonance methods, the modified Mosher's method, and X-ray diffraction analysis. Based on analysis of NOESY correlations and the modified Mosher's method, the stereochemistry of two known furodysinane-type sesquiterpenoids were revised. A plausible biogenetic relationship between these sesquiterpenoids wasproposed and discussed, and a chemo-ecological relationship of the title animal and its possible sponge preys has been analyzed. In bioassays, sanyagunin B showed moderate antibacterial activity, whereas 4α-formamidogorgon-11-ene exhibited potent cytotoxicity with IC50 values ranging from 0.87 to 1.95 µM.

Structurally Diverse Diterpenoids from the Sanya Bay Nudibranch Hexabranchus sanguineus and Its Sponge-Prey Chelonaplysilla sp.

Investigation of the South China Sea nudibranch Hexabranchus sanguineus from Sanya Bay afforded, in addition to three known compounds, nine new diterpenoids of the 5,19-cycloclerodane- (sanyanolides A-D), clerodane- (sanyanolide E) and subersin- (sanyanolides F-I) type. Remarkably, six diterpenoids aforementioned from H. sanguineus were also isolated from the sponge Chelonaplysilla sp. from the same water region, suggesting a trophic relationship between H. sanguineus and Chelonaplysilla sp. The structure and absolute configuration of new compounds were established by a combination of spectroscopic data, X-ray diffraction analysis and/or time-dependent density functional theory/electronic circular dichroism calculations. A plausible biogenetic relationship between these diterpenoids, along with the chemo-ecological implications of their co-occurrence in the two organisms investigated, was proposed and discussed. In in vitro bioassays, echinoclerodane A exhibited a potent inhibitory effect (IC50 =2.81 µM) on LPS-induced inflammatory response in RAW 264.7 macrophage cells. In addition, echinoclerodane A and oculatolide showed considerable antibacterial activities with MIC values ranging from 1.0 to 8.0 µg/mL.

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa.

One new aromadendrane-type sesquiterpenoid, namely ximaocavernosin P [(+)-1], and three new cadinane-type sesquiterpenoids, namely (+)-maninsigin D [(+)-4], (+)- and (-)-ximaocavernosin Q [(+)- and (-)-5], together with five related known ones [2, 3, (-)-4, 6, and 7], were isolated from the Hainan sponge Acanthella cavernosa. Compounds 4 and 5 were isolated as racemic forms, which were further separated to the corresponding enantiomers [(+)-4/(-)-4 and (+)-5/(-)-5], respectively, by using chiral-phase HPLC. The structures of new compounds were elucidated by extensive spectroscopic analysis and comparison with the reported data. In addition, the absolute configuration of optically pure (+)-1 and 2 were determined by time-dependent density functional theory/electronic circular dichroism (TDDFT-ECD) calculations or X-ray diffraction analysis. A plausible biosynthetic pathway of these sesquiterpenoids and their internal correlation were proposed and discussed. In an in vitro bioassay, (+)-aristolone (3) exhibited promising anti-inflammatory activity by the inhibition of LPS-induced TNF-α and CCL2 release in RAW 264.7 macrophages.

Stereochemical insights into neuroprotective alkaloids from the aerial parts of Emilia sonchifolia.

A new alkaloid featured with a dibenz[c,e]azepin-5-one scaffold, namely emililactam A (3), together with a known pyrrolidine alkaloid (emilisonchine, 1) and a known flavonoid alkaloid [8-(2″-pyrrolidinone-5″-yl)-quercetin, 2] were isolated from the aerial parts of Emilia sonchifolia. Compounds 1 and 2 were isolated as racemic forms which were further separated, for the first time, to their corresponding enantiomers [(+)-1/(-)-1 and (+)-2/(-)-2], respectively, by using chiral-phase HPLC. The structure of new compound 3 was elucidated by extensive spectroscopic analysis. In addition, the absolute configurations of optically pure (+)-1/(-)-1 and (+)-2/(-)-2 were determined by the time-dependent density functional theory electronic circular dichroism (TDDFT-ECD) calculations. In an in vitro bioassay, compounds (+)-1, (-)-1, (±)-1, and 3 exhibited moderate neuroprotective effects against corticosterone-induced injuries of PC12 cells.

Pitfalls in the structural elucidation of small molecules. A critical analysis of a decade of structural misassignments of marine natural products.

Covering: July 2010 to August 2021This article summarizes more than 200 cases of misassigned marine natural products reported between July 2010 and August 2021, sorting out errors according to the structural elements. Based on a comparative analysis of the original and the revised structures, major pitfalls still plaguing the structural elucidation of small molecules were identified, emphasizing the role of total synthesis, crystallography, as well as chemical- and biosynthetic logic to complement spectroscopic data. Distinct "trends" in natural product misassignment are evident between compounds of marine and plant origin, with an overall much lower incidence of "impossible" structures within misassigned marine natural products.

Chemical and biological studies of Daphniphyllum oldhamii from Hunan Province, China.

The fruits, twigs and leaves of Daphniphyllum oldhamii (Hemsl.) K. Rosenthal, collected from Longshan County, Hunan Province, China, were chemically investigated. Three undescribed daphniphyllum alkaloids, namely longshanoldhamines A‒C, and six known related ones have been isolated from the fruits, whereas two undescribed triterpenoids and one undescribed lignan, along with six known triterpenoids, were found in the twigs and leaves. Their structures were elucidated by extensive spectroscopic analysis, X-ray diffraction analysis and comparison with the reported data.

Ximaoglaucumins A - F, new cembranoids with anti-inflammatory activities from the South China Sea soft coral Sarcophyton glaucum.

Six new cembrane-type diterpenoids, namely ximaoglaucumins A-F (1-6), along with fifteen known related ones (7-10 and 14-24), have been isolated from the soft coral Sarcophyton glaucum collected off the Ximao Island in the South China Sea. Their structures, including absolute stereochemistry, were elucidated by extensive spectroscopic analysis, quantum mechanical nuclear magnetic resonance (QM-NMR) methods, X-ray diffraction analysis, chemical methods, as well as comparison with the reported data in the literature. Further, detailed analysis of spectroscopic data of 7 not only clarified the confusions regarding 7, 11 (sarcophytolol) and 12/13 (sarcotrocheliol) in the literature, but also led to revise the structure of 11, which was mis-assigned due to careless/erroneous interpretation of the 2D NMR spectra, and to correct the structures of 12/13, which were both wrongly depicted. In in vitro bioassay, compounds 8 and 20 exhibited potent inhibitory effects on lipopolysaccharide (LPS)-induced inflammatory responses in BV-2 microglial cells.

[Chemical constituents contained in aerial parts of Emilia sonchifolia].

OBJECTIVE: To study the chemical constituents contained in ethanol extracts from aerial parts of Emilia sonchifolia. METHOD: The compounds were separated and purified with various chromatographic techniques, and their structures were identified on the basis of physicochemical properties and spectral data. RESULT: Fifteen compounds were separated from ethyl acetate fraction of 90% ethanolic extract and identified as rhamnetin (1), isorhamnetin (2), quercetin (3), luteolin (4), tricin-7-O-beta-D-glucopyranoside (5), 8-(2"-pyrrolidinone-5"-yl) -quercetin (6), 5, -2', 6'-trihydroxy-7, 8-dimethoxyflavone-2'-O-beta-D-glucopyranoside (7), succinic acid (8), fumaric acid (9), p-hydroxybenzoic acid (10), 4-hydroxy isophthalic acid (11), 3, 4-dihydroxycinnamic acid (12), esculetin (13), isowedelolactone (14) and uracil (15), respectively. CONCLUSION: All compounds except compound 3 were separated from this genus for the first time.