New Cembrane Diterpenes from Taiwanese Soft Coral Sinularia flexibilis

Anti-HBV Activities of Cembranoids from the South China Sea Soft Coral Sinularia pedunculata and Their Structure Activity Relationship

Hepatitis B Virus (HBV) infection is a global public health challenge that seriously endangers human health. Soft coral, as a major source of terpenoids, contains many structurally novel and highly bioactive compounds. Sixteen cembranoids (1-16), including a new one named sinupedunol B (16), were isolated from the South China Sea Soft coral Sinularia pedunculata. The structure of the sinupedunol B (16) was determined through a combination of spectroscopic analysis and X-ray single-crystal diffraction. In this study, cembranoids isolated from Sinularia pedunculata were found of anti-HBV activity for the first time. Among them, flexilarin D (6) showed significant anti-HBV activity with an IC50 value of 5.57 μM without cytotoxicity. We then analyzed the structure-activity relationship (SAR). Furthermore, it is demonstrated that flexilarin D (6) can accelerate the formation of capsid, inhibit HBeAg, HBV core particle DNA, HBV total RNA and pregenomic RNA in a dose dependent manner. We also confirmed the anti-HBV activity of 6 in HepG2-NTCP infection system. Finally, we demonstrated the anti-HBV mechanism of these compounds by inhibiting the ENI/Xp enhancer/promoter.

Cembrane diterpenoids: Chemistry and pharmacological activities

Cembrane diterpenoids (cembranoids), characterized by a 14-membered carbon ring and wide variety of functional groups, found in marine and terrestrial organisms. Many studies have shown that cembrane diterpenoids have cytotoxic and anti-inflammatory activities and are widely used in the development of new drugs. This review covered publications from 2011 to 2022 and classified the cembrane-type diterpenoids into isopropyl (ene) type, γ-lactone or unsaturated five-membered ring, δ-lactone or unsaturated six-membered ring, ε-lactone or unsaturated seven-membered ring, and other cembrane diterpenes. In addition, the biological activity and structure-activity relationship were summarized. This will provide guidance for new cembrane-type diterpenes as lead compounds to explore their potential application for treating cancer and inflammatory diseases.

Recent updates on Sinularia soft coral

Marine organisms are recognized as a rich source of bioactive secondary metabolites. The remarkable abundance and diversity of bioactive small molecules isolated from soft corals displayed their essential role in drug discovery for human diseases. Sterols and terpenes, particularly cembranolides, 14-membered cyclic diterpene, demonstrated numerous biological activities, such as antitumor, antimicrobial, antiviral, antidiabetic, anti-osteoporosis and anti-inflammatory. Accordingly, continuous investigation of marine soft corals will be the way for the discovery of a plentiful number of chemical diverse natural products with various biological potentials for prospective pharmaceutical industrial applications. Such review affords plenary inspection of the total secondary metabolites isolated from the Sinularia, from 2008 until 2020, besides their natural sources as well as bioactivities whenever possible.

Cembrane derivatives from the soft corals, Sinularia gaweli and Sinularia flexibilis

A new norcembranoidal diterpene, 1-epi-sinulanorcembranolide A (1), and a new cembranoidal diterpene, flexibilin D (2), were isolated from the soft corals, Sinularia gaweli and Sinularia flexibilis, respectively. The structures of new metabolites 1 and 2 were elucidated by spectroscopic methods, and compound 2 was found to significantly inhibit the accumulation of the pro-inflammatory iNOS and COX-2 proteins of the lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. In addition, S. flexibilis yielded a known cembrane, 5-dehydrosinulariolide (3); the structure, including its absolute stereochemistry, was further confirmed by single-crystal X-ray diffraction analysis.

Flexibilins A-C, new cembrane-type diterpenoids from the Formosan soft coral, Sinularia flexibilis

Three new cembrane-type diterpenoids, flexibilins A-C (1-3), along with a known cembrane, (-)-sandensolide (4), were isolated from the soft coral, Sinularia flexibilis. The structures of cembranes 1-4 were elucidated by spectroscopic methods. The structure of 4, including its absolute stereochemistry, was further confirmed by single-crystal X-ray diffraction analysis. Cembrane 2 displayed a moderate inhibitory effect on the release of elastase by human neutrophils.

Norcembranoidal diterpenes from a Formosan soft coral Sinularia sp

Two norcembranoidal diterpenes, 5-episinuleptolide acetate (1) and scabrolide D (2), were isolated from a Formosan octocoral identified as Sinularia sp. The structures of norcembranoids 1 and 2 were established by spectroscopic methods and by comparison of the spectral data with those of known analogues and 1 was proven to be a new natural product. Norcembranoid 1 was found to exhibit cytotoxicity toward a panel of tumor cells.

New cembrane diterpenoids from a Hainan soft coral Sinularia sp

Five new cembrane diterpenoids, named sinuflexibilins A-E (1-5), along with nine other known diterpenoids (6-14), have been isolated from the organic extract of a Hainan soft coral Sinularia sp. Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites. Compound 13, flexibilide, exhibited significant inhibitory activity of NF-κB activation using the cell-based HEK293 NF-κB luciferase reporter gene assay.

Marine natural products

Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1003 for 2010), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.