Study the molecule species of phosphatidylethanolamine class in soft coral \(\textit{Sinularia flexibilis}\) lipid at different times of the year

Samples of soft coral Sinularia flexibilis were collected in February, May, August, November in Nha Trang, Khanh Hoa. The content of molecular species in phosphatidylethanolamine class in the lipid of obtained coral samples has been determined. Identified 14 types of PE molecule species, in which the alkenylacyl PE 18:1e/20:4 has the highest concentration, ranging from 51.35% to 63.16% in 4 samples, the highest and lowest concentrations were in a sample collected in August and November, respectively. Samples collected in August and May have a lower diacyl PE ratio than samples collected in November and February. This study identified the lowest alkylacyl and the highest alkenylacyl concentration in a sample collected in August. The fatty acids present in this class are 17:1, 18:1, 18:2, 19:1, 20:4, and 24:5. The percentage of the total content of molecule species by each fatty acid is similar between months. The total content of molecule species containing 20:4n fatty acids was 80.08–84.27% of the PE class, and the difference was not significant in 4 coral samples. There was an inverse correlation between the total content of molecule species containing 20:4n PUFA and the total content of 20:4n fatty acid and the proportional correlation between the content of PE molecule species containing 24:5n PUFA content of 24:5n fatty acid in total fatty acids.

Anti-Acne Effects of Cembrene Diterpenoids from the Cultured Soft Coral Sinularia flexibilis

Acne is a skin disease common in adolescents and increasingly common in the adult population. The major pathologic events of acne vulgaris include increased sebum production, retention hyperkeratosis, carrying commensal skin microbiota, and inflammation. In recent years, more than 10,000 compounds have been isolated and identified from marine organisms. The aim of this study was to discover the potential anti-acne activity of fraction 9 + 10 (SF-E) of Sinularia flexibilis extract and six cembrene diterpenoids. We found that the SF-E significantly reduced Cutibacterium acnes-induced edema in Wistar rat ears. The cembrene diterpenoids including 11-dehydrosinulariolide (SC-2), 3,4:8,11-bisepoxy-7-acetoxycembra-15(17)-en-1,12-olide (SC-7), and sinularin (SC-9) reduced nitric oxide (NO) production with 50% inhibitory concentration of 5.66 ± 0.19, 15.25 ± 0.25, and 3.85 ± 0.25 μM, respectively, and inducible NO synthase expression in RAW 264.7 cells. Moreover, treatment with SC-2, SC-7, and SC-9 significantly suppressed lipopolysaccharide- and heat-killed C. acnes-induced expression of proteins involved in mitogen-activated protein kinase pathway in both RAW 264.7 and HaCaT cells. After treatment with SC-2, SC-7, and SC-9, over-proliferation of HaCaT cells was significantly terminated. In summary, SC-2, SC-7, and SC-9 showed anti-inflammatory effects in RAW 264.7 cells, suggesting that these cembrene diterpenoids obtained from S. flexibilis are natural marine products with potential anti-acne activities.

The discovery of potential natural products for targeting SARS-CoV-2 spike protein by virtual screening

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters into the cells through its spike proteins binding to human angiotensin-converting enzyme 2 (ACE2) protein and causes virus infection in host cells. Until now, there are no available antiviral drugs have been reported that can effectively block virus infection. The study aimed to discover the potential compounds to prevent viral spike proteins to bind to the human ACE2 proteins from Taiwan Database of Extracts and Compounds (TDEC) by structure-based virtual screening. In this study, to rapidly discover potential inhibitors against SARS-CoV-2 spike proteins, the molecular docking calculation was performed by AutoDock Vina program. Herein, we found that 39 potential compounds may have good binding affinities and can respectively bind to the viral receptor-binding domain (RBD) of spike protein in the prefusion conformation and spike-ACE2 complex protein in silico. Among those compounds, especially natural products thioflexibilolide A and candidine that were respectively isolated from the soft corals Sinularia flexibilis and Phaius mishmensis may have better binding affinity than others. This study provided the predictions that these compounds may have the potential to prevent SARS-CoV-2 spike protein from entry into cells.

A New Method for Collecting Large Amounts of Symbiotic Gastrodermal Cells from Octocorals

The study of cnidarian-dinoflagellate endosymbiosis in octocorals is becoming increasingly important. As symbiotic gastrodermal cells (SGCs) are the key cells in a symbiotic relationship, obtaining SGCs and studying their functions represent an urgent need. The majority of the cells dissociated from octocoral tissues consist of host cells and algal cells, and very few intact SGCs can be observed. To solve this problem, we developed a new method to collect large amounts of SGCs from octocorals. We incubated the tissue of Sinularia flexibilis in high-salinity (60‰) filtered seawater for 6 h and were able to collect more than 18 times the number of SGCs from the control group. To test the quality of the dissociated cells, we performed three assays to evaluate their cell viability. All three assays demonstrated that cell viability was good after incubating in a high-salinity solution. We also used two other octocorals, Paralemnalia thyrsoides and Sinularia compressa, to perform the same experiment, and the results were similar to those for Sinularia flexibilis. Therefore, a high-salinity-induced increase in the SGC ratio is a common phenomenon among octocorals. This method allows researchers to collect large amounts of SGCs from octocorals and helps us to better understand the complex molecular interactions in cnidarian-dinoflagellate endosymbiosis.

Study on total lipid content, lipid class composition of some fire and soft corals collected in Nha Trang, Vietnam

For the first time, the total lipid content and lipid class composition of the Vietnamese soft corals (Sinularia brassica, Sinularia flexibilis) and fire corals (Millepora dichotoma, Millepora platyphylla) were investigated. The results indicated that the total lipid content of the investigated species was significantly different. Compositions of the lipid classes were analyzed using TLC and image analysis program Sorbfil TLC Videodensitometer DV and the results showed that phospholipids (PL, 10.91–16.02%), monoalkyldiacylglycerols (MADAG, 20.69-39.92%) and hydrocarbon wax (HW, 29.83-37.17%) were the main lipid classes of the total lipid in soft coral species. Meanwhile, PL (24.11-33.23%), TG (14.27–34.92%), ST (10.10–14.50%) and HW (12.08–19.95%) were predominant in fire coral species. ST, TG and FFA contents in soft and fire corals were at low level. DG was only present in the Sinularia flexibilis but not in other studied corals.

Sandensolide Induces Oxidative Stress-Mediated Apoptosis in Oral Cancer Cells and in Zebrafish Xenograft Model

Presently, natural sources and herbs are being sought for the treatment of human oral squamous cell carcinoma (OSCC) in order to alleviate the side effects of chemotherapy. This study investigates the effect of sandensolide, a cembrane isolated from Sinularia flexibilis, to inhibit human OSCC cell growth with the aim of developing a new drug for the treatment of oral cancer. In vitro cultured human OSCC models (Ca9.22, SCC9 and HSC-3 cell lines) and oral normal cells (HGF-1), as well as a zebrafish xenograft model, were used to test the cytotoxicity of sandensolide (MTT assay), as well as to perform cell cycle analysis and Western blotting. Both the in vitro bioassay and the zebrafish xenograft model demonstrated the anti-oral cancer effect of sandensolide. Moreover, sandensolide was able to significantly suppress colony formation and induce apoptosis, as well as cell cycle arrest, in OSCC by regulating multiple key proteins. Induction of reactive oxygen species (ROS) was observed in sandensolide-treated oral cancer cells. However, these apoptotic changes were rescued by NAC pretreatment. These findings contribute to the knowledge of the model of action of sandensolide, which may induce oxidative stress-mediated cell death pathways as a potential agent in oral cancer therapeutics.

Cembranoid-Related Metabolites and Biological Activities from the Soft Coral Sinularia flexibilis

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.