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Soft corals are well-known as excellent sources of marine-derived natural products. Among them, members of the genera Sarcophyton, Sinularia, and Lobophytum are especially attractive targets for marine natural product research. In this review, we reported the marine-derived natural products called cembranoids isolated from soft corals, including the genera Sarcophyton, Sinularia, and Lobophytum. Here, we reviewed 72 reports published between 2016 and 2020, comprising 360 compounds, of which 260 are new compounds and 100 are previously known compounds with newly recognized activities. The novelty of the organic molecules and their relevant biological activities, delivered by the year of publication, are presented. Among the genera presented in this report, Sarcophyton spp. produce the most cembranoid diterpenes; thus, they are considered as the most important soft corals for marine natural product research. Cembranoids display diverse biological activities, including anti-cancer, anti-bacterial, and anti-inflammatory. As cembranoids have been credited with a broad range of biological activities, they present a huge potential for the development of various drugs with potential health and ecological benefits. [ABSTRACT FROM AUTHOR]

Herein, we provide observation on the ecological relationships between the hydrozoan species Pteroclava krempfi and three alcyonacean genera: Lobophytum, Sarcophyton and Sinularia from protected and exposed reef habitats in the Maldives. The associations were found to be widespread in the investigated area with both an overall and taxon-specific symbiosis prevalence higher in the exposed reef sites. Pteroclava krempfi most frequently occurred with Lobophytum, followed by Sinularia and Sarcophyton. The prevalence of P. krempfi with soft corals was also positively correlated to percent host cover, which was higher in the outer reef sites, suggesting a host-reliant relationship for the hydrozoan. However, the nature of these relationships, as as well as the factors that drive their establishment, requires further investigation. The widespread degradation of coral reef ecosystems endangers the existence of many poorly understood, but intimate relationships that often go unrecognized. [ABSTRACT FROM AUTHOR]

Three cadinane-type sesquiterpenoids, endoperoxide ( 1) and hydroperoxides ( 2, 3) together with three known sesquiterpenoids ( 4- 6) were isolated from an Okinawan soft coral, Sinularia species. Structures of these isolates were elucidated by spectroscopic analyses (NMR, IR and MS) and molecular modeling. In addition, the isolates 1- 3 as new compounds were examined for biological activities, resulting that they have antibacterial activity and weak cytotoxicity against HCT116 cells as well as anti-inflammatory effect on LPS/IFN-γ-stimulated RAW 264.7 macrophage cells. [ABSTRACT FROM AUTHOR]

Bioassay-guided fractionation of the marine sponge Lendenfeldia dendyi and the soft coral Sinularia dura resulted in the isolation of five polybrominated diphenyl ethers ( 1-5). The structures of the isolated compounds were determined using spectroscopic methods (1D and 2D NMR) and HRMS analyses. The absolute structures of compounds 1 and 2 were confirmed by X-ray analysis. Antimicrobial testing of the isolated compounds along with the acetylated derivative of compound 2 ( 2a) indicated that they displayed a significant and selective activity against methicillin-resistant Staphylococcus aureus (MRSa) with IC values of <0.04-1.18 µM. The antimalarial and antileishmanial activities of the isolated compounds were also evaluated. [ABSTRACT FROM AUTHOR]

The application of DNA barcoding to anthozoan cnidarians has been hindered by their slow rates of mitochondrial gene evolution and the failure to identify alternative molecular markers that distinguish species reliably. Among octocorals, however, multilocus barcodes can distinguish up to 70 % of morphospecies, thereby facilitating the identification of species that are ecologically important but still very poorly known taxonomically. We tested the ability of these imperfect DNA barcodes to estimate species richness in a biodiversity survey of the shallow-water octocoral fauna of Palau using multilocus ( COI, mtMutS, 28S rDNA) sequences obtained from 305 specimens representing 38 genera of octocorals. Numbers and identities of species were estimated independently (1) by a taxonomic expert using morphological criteria and (2) by assigning sequences to molecular operational taxonomic units (MOTUs) using predefined genetic distance thresholds. Estimated numbers of MOTUs ranged from 73 to 128 depending on the barcode and distance threshold applied, bracketing the estimated number of 118 morphospecies. Concordance between morphospecies identifications and MOTUs ranged from 71 to 75 % and differed little among barcodes. For the speciose and ecologically dominant genus Sinularia, however, we were able to identify 95 % of specimens correctly simply by comparing mtMutS sequences and in situ photographs of colonies to an existing vouchered database. Because we lack a clear understanding of species boundaries in most of these taxa, numbers of morphospecies and MOTUs are both estimates of the true species diversity, and we cannot currently determine which is more accurate. Our results suggest, however, that the two methods provide comparable estimates of species richness for shallow-water Indo-Pacific octocorals. Use of molecular barcodes in biodiversity surveys will facilitate comparisons of species richness and composition among localities and over time, data that do not currently exist for any octocoral community. [ABSTRACT FROM AUTHOR]

Alcyonacean octocorals in tropical reefs are usually not considered as reef builders. Some Sinularia species, however, are capable of consolidating sclerites at the colony base to form spiculite. Nanwan Bay, southern Taiwan, features both fossilized and recently formed boulders composed of spiculite, thus demonstrating the role of Sinularia in contributing to the reef structure. Section radiography of an 18.5 kg spiculite boulder demonstrated a regular density banding of 3-6-mm intervals. Core survey indicated spiculite coverage of 25-30% on the live reef and of 30-40% on the uplifted boulders. Cores taken from living Sinularia revealed a distinct transition from discrete sclerites to compact spiculite and amorphous calcium carbonate cementing the sclerites. In the widespread S. gibberosa, sclerite formation appeared to start intracellularly, followed by a prolonged extracellular calcification process. At the calcification site, multiple sclerocytes formed expanded pseudopod-like membranes that interconnected, forming multicellular vesicles (MCVs) around the sclerites. The MCVs and the pseudopods disappeared at sclerite maturation, followed by degradation of the sclerocytes around the mature sclerites. At the colony base, granular vesicles were distributed among the sclerites, indicating a cementing process in progress. These findings suggest that colonies of Sinularia are able to cement sclerites and consolidate them at their base into spiculite, thus making them reef builders. [ABSTRACT FROM AUTHOR]

Two metabolites featuring norcembranoid diterpene skeleton have been isolated from chloroform extract of soft coral of the genus sinularia, which was collected from the southern coast of India. The structures of the metabolites were determined by 1D, 2D NMR spectroscopic data and HRESIMS data analysis. The compounds have shown moderate-to-high antimicrobial activities. The structure and the relative stereochemistry of the metabolite 1 have been determined by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The resilience of Symbiodinium harboured by corals is dependent on the genetic diversity and extent of connectivity among reef populations. This study presents genetic analyses of Great Barrier Reef (GBR) populations of clade C Symbiodinium hosted by the alcyonacean coral, Sinularia flexibilis. Allelic variation at four newly developed microsatellite loci demonstrated that Symbiodinium populations are genetically differentiated at all spatial scales from 16 to 1,360 km (pairwise ΦST = 0.01-0.47, mean = 0.22); the only exception being two neighbouring populations in the Cairns region separated by 17 km. This indicates that gene flow is restricted for Symbiodinium C hosted by S. flexibilis on the GBR. Patterns of population structure reflect longshore circulation patterns and limited cross-shelf mixing, suggesting that passive transport by currents is the primary mechanism of dispersal in Symbiodinium types that are acquired horizontally. There was no correlation between the genetic structure of Symbiodinium populations and their host S. flexibilis, most likely because different factors affect the dispersal and recruitment of each partner in the symbiosis. The genetic diversity of these Symbiodinium reef populations is on average 1.5 times lower on inshore reefs than on offshore reefs. Lower inshore diversity may reflect the impact of recent bleaching events on Sinularia assemblages, which have been more widespread and severe on inshore reefs, but may also have been shaped by historical sea level fluctuations or recent migration patterns. [ABSTRACT FROM AUTHOR]

Sinularia polydactyla, an abundant Indo-Pacific soft coral species, exhibits biochemical phenotypic plasticity, prompting investigations into differences in mRNA diversity and complexity in response to predation stress. Changes in transcriptome complexity of S. polydactyla cDNA libraries were measured using reannealing rate assays that employ an informatics-based analysis of kinetic profiles. This method allows for quick, high-throughput analysis of sequence complexity and has been used to compare transcriptome-level differences in other marine invertebrates. Here, S. polydactyla colonies were transplanted between two sites exhibiting high and low predation levels. Statistically significant differences between bite scar counts found on different transplant groups suggest site-specific variation in predation. Changes in mRNA pool complexity were quantified to indicate shifts in secondary metabolite concentration between treatment groups. Examining the complexity of the mRNA pool in this soft coral is one of the first steps toward understanding the mechanisms of phenotypic plasticity at a biochemical and molecular level. [ABSTRACT FROM AUTHOR]

We evaluated the role that demography may play in the formation of local aggregations ofSinularia flexibilis(Quoy&Gaimard, 1833), a soft coral that commonly dominates inshore coral reefs of the Great Barrier Reef (GBR), Australia. Two populations on inshore reefs of the Palm Islands were censused once a year for 3?years, starting 10 mo after the extensive bleaching mortality in early 1998. Larger colonies became more prevalent over time; mean colony size increasing by 35%, from 276 cm2 in 1998 to 373 cm2 in 2000. Growth rates were size dependent, with smaller colonies growing proportionally faster than larger colonies. Change in size relative to initial size indicated an expected mean annual growth of 128 cm2 for a 50-cm2 colony. Zero growth was predicted at 532±21cm2, with colonies larger than this likely to undergo fission or shrink. Forty-three percent of colonies were undergoing fission at any time at both localities. Most new colonies were produced by fission (70%,n=285), with the remainder produced by the recruitment of sexually produced larvae (19%) or by colony translocation (11%). The sexual and asexual recruitment rates were 0.24 and 1.0 recruits m-2 year?1, respectively. Opportunistic recruitment and rapid growth following disturbances are commonly assumed to be the mechanisms leading soft corals to dominate locally. In this study, these mechanisms operated more slowly than expected, with no net change in population size. [ABSTRACT FROM AUTHOR]