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A phytochemical investigation of an East China Sea collection of the brown alga Dictyota coriaceahas led to the isolation of four novel nitrogen-containing crenulide diterpenoids, named coriaceumins A–D (1–4), two rare nitrogenous xenicane diterpenoids, dictyolactams C (5) and D (6), and one known crenulide diterpenoid, hydroxycrenulide (7). The structures of the new compounds were elucidated by detailed spectroscopic data analyses, including HRESIMS and 1D/2D NMR. The absolute configurations were determined by a comparison of the experimental ECD spectra with the spectra computed by DFT-based quantum chemical calculations. Coriaceumins A–D (1–4) represent the first examples of nitrogen-containing crenulide diterpenoids. In a bioassay, compounds 2, 3, 5, and 7were found to exhibit different levels of inhibitory effects against protein tyrosine phosphatase 1B (PTP1B) with IC50values ranging from 7.3 to 19 μM. In addition, the primary structure–activity relationships of all the isolates were summarized.

Marine invertebrates serve as rich sources of secondary metabolites with intriguing chemical diversities and a wide spectrum of biological activities. Particularly, marine shell-less sacoglossan mollusks have attracted much attentions due to the fact that mollusks apply complex metabolites as chemical defense agents against to their predators. With the purpose of discovering bioactive secondary metabolites to develop marine-derived medicines from the South China Sea, we have conducted a chemical study on the photosynthetic mollusk Placobranchus ocellatus.As a result, seven new γ-pyrone polypropionates, namely ( ±)-ocellatuspyrone A (1), ( ±)-ocellatuspyrone B (2), and ocellatuspyrones C−G (5, 9−12), along with five known polypropionates, have been isolated and characterized from the South China Sea photosynthetic mollusk Placobranchus ocellatus. Extensive spectroscopic analysis, single crystal X-ray diffraction analysis, modified Mosher’s method, ECD comparison, CD exciton chirality method, TDDFT-ECD calculation, and chemical conversion were used to determine the structures and absolute configurations of the new compounds and the stereochemistry of undefined known compounds 4, 6and 7. All these isolated polypropionates were evaluated in bioassays for their biological activities, including antibacterial, neuroprotective effect, anti-inflammatory, PTP1B inhibitory, and antiviral activities. Compounds 7, 8and 11were found for the first time to show antibacterial activity against fish pathogenic bacteria Streptococcus parauberis(the main pathogen causing fish streptococcal infections and acute death) with MIC values of 35.8, 34.2, and 37.4 μg/mL, respectively, which might be potential novel antibacterial agents for the treatment of fish infectious diseases.

Graphical abstract: The accurate testing protocols of NF membranes were clarified, which is important for the development of advanced nanofiltration materials.

Litosetoenins A–E (1–5), five new ring-rearranged serrulatane-type diterpenoids with a common tricyclo[3.0.4]decane core, along with a known diterpenoid glycoside (6), a related known diterpenoid (7), and four known sesquiterpenoids (8–11), were isolated from a Balinese soft coral Litophyton setoensis. Spirolitosetoenin A (5a) and isospirolitosetoenin A (5b), featuring an unprecedented spiro[4,5]decane core, were obtained after treatment of compound 5with HCl in methanol. The structures of new compounds were elucidated by extensive spectroscopic analysis, quantum mechanical nuclear magnetic resonance approach, and chemical methods. A plausible biosynthetic pathway involving an unusual divergent biogenesis was proposed.

Two novel rearranged Diels–Alder adducts, morunigrines A (1) and B (2), and four new prenylated flavonoids, morunigrols A–D (3–6), were isolated from the twigs of Morus nigra, together with four known prenylated phenolic compounds, including two flavonoids (7and 8) and two 2-arylbenzofurans (9and 10). Morunigrines A (1) and B (2) are a novel class of Diels–Alder adducts with unprecedented carbon skeletons featuring a rearranged chalcone–stilbene/2-arylbenzofuran core decorated with a unique methylbiphenyl moiety. The structures of the new compounds were assigned by analysis of spectroscopic data. The absolute configuration of compound 6was determined by the measurement of specific rotation. A plausible biogenetic pathway for 1and 2is also proposed. Compounds 1and 2exhibited more potent protein tyrosine phosphatase 1B inhibitory activity with IC50values of 1.8 ± 0.2 and 1.3 ± 0.3 μM, respectively, than that of the positive control oleanolic acid (IC50, 2.5 ± 0.1 μM).

The dietary relationship study between marine sponge Xestospongiasp. and its nudibranch predators Jorunna funebrisbased on the discovery of isoquinolinequinones has long been studied. In this study, chemical investigation of the sponge Xestospongiasp. and nudibranch J. funebrisfrom the South China Sea yielded a new marine alkaloid neopetroside C (1), together with nine known alkaloids (2–10). The chemical structures of all the compounds were elucidated by extensive spectroscopic analysis. Neopetroside C (1) featured a riboside of nicotinic acid with a rare α-Nglycosildic linkage and an acyl residue of (Z)-2-methylbut-2-enoic acid attached to C-5′. The plausible chemical ecology relationship between sponge Xestospongiasp. and its nudibranch predator J. funebriswas proposed based on the biogenetic relationship of the common marine alkaloids. The observation of two structural fragments, (Z)-2-methylbut-2-enoyloxy and trigonelline groups in both sponge and nudibranch, indicated that nudibranch might uptake chemicals from sponge and then modify and transform them into chemical weapons to defend against predators.

Marine mollusks are a prolific source of secondary metabolites with complex/diverse structures and various aspects of biological activities. For the above-mentioned reason, these animals have been extensively explored and have become the hotspot of the research subject in recent years. It is well documented that mollusks can escape from predation by utilizing bioactive metabolites as defensive chemicals. In the last decade, the possible diet relationship between the South China Sea mollusks and their related potential prey organisms, including sponges, corals, algae, etc. has been systematically investigated. A series of interesting results have been obtained concerning the chemistry, chemoecology, and pharmacological profiles of the studied marine organisms. The present review focuses on recent developments dealing with chemistry, chemoecology, and bioactivity of the South China Sea mollusks and their dietary organisms.

Abstract: A phytochemical investigation of the EtOH extract of the flowers of Lagerstroemia indicaL. led to the isolation and characterization of a new pyrrole alkaloid, named lagerindicine (1), along with four known compounds (2–5). Their structures were elucidated by the detailed spectroscopic analysis and comparison with literature data, whereas the structure, in particularly, the absolute configuration (AC) of 1, was firmly determined by total synthesis. All the isolates were evaluated for their cytotoxic effects against human colon cancer cell (HCT-116), and compound 3exhibited weak cytotoxicity with IC50value of 28.4 μM. Graphic Abstract:

Two new macrocyclic cembranoids were isolated from the South China Sea soft coral Lobophytumsp. Quantum mechanical–nuclear magnetic resonance (QM–NMR) methods were decisive in their structural elucidation. Better performance in arriving at definitive structures was obtained by QM–NMR methods upon incorporation of 3JHHvalues. The validity of this approach also supported an alternative conformational proposal versus that obtained by X-ray crystallography.

The simulation technology of 3D cloud can be the ideal method to meet both making human visual scenes realistic and generating weather radar images in flight simulations. This paper describes a 3D cloud simulation method and technology that focuses in three aspects of cloud modeling, lighting and rendering. Firstly, the 3D cloud was modeled in a particle system to specify the atmosphere characteristics of cloud in natural world, then the textures were mapped to the particles to improve the cloud authentic and the lighting model was established to make the cloud environments realistic. Finally, the impostor technology was used to accelerate the rendering speed. The implementation on PC platform shows that the method and technology can generate realistic 3D cloud and the real time ability is satisfied.

A numerical study using computational fluid dynamics (CFD) under air/water two-phase flow condition without thermal transmission is carried out utilizing the commercial CFD code CFX. A detailed geometry of 5×5 rod bundles with two grid spacers in the Pressurized Water Reactor (PWR) is set up for analyzing. The Multiple Size Group (MUSIG) model based on the population balance equation is employed to describe the characteristic of flow field in which the dispersed phase has a large variation in size, and the breakup and coalescence interaction among different sizes of the bubbles. The effects of the size fraction at inlet, the size group quantities, the breakup and coalescence coefficients, the momentum transfer model, and so on, are studied. The results demonstrate that various parameters and two-phase model have different impacts on the analysis results. The detailed CFD modeling methodology for two-phase flow conditions in PWR fuel assemblies is developed according to the above-mentioned investigations. The flow field patterns and air/water phase distributions in the computational results shows that the two-phase modeling methodology in the present work is reasonable.