Terpenoids from the Soft Coral Sinularia densa Collected in the South China Sea.

The chemical investigation of the South China Sea soft coral Sinularia densa has resulted in the isolation of seven new terpenoids, including two new meroterpenoids, namely sinudenoids F-G (1-2), and five new cembranes, namely sinudenoids H-L (3-7). Their structures and absolute configurations were elucidated based on extensive analyses of spectroscopic data, single-crystal X-ray diffraction, comparison with the literature data, and quantum chemical calculations. Among them, sinudenoid F (1) and sinudenoid G (2) are rare meroterpenoids featuring a methyl benzoate core. Sinudenoid H (3) possesses a rare carbon skeleton of 8, 19-bisnorfuranocembrenolide, which is the second reported compound with this skeleton. In a bioassay, sinudenoid H (3) exhibited better anti-inflammatory activity compared to the positive control indomethacin at 20 µM in CuSO4-treated transgenic fluorescent zebrafish. Moreover, sinudenoid J (5) and sinudenoid L (7) exhibited moderate anti-thrombotic activity in arachidonic acid (AA)-induced thrombotic zebrafish at 20 µM.

Structural Investigation of Aaptourinamine by a Novel Module-Assembly-Based Calculation.

Natural products have various and complicated structures, which is still a challenge for elucidating these compounds, especially for those lacking two-dimensional nuclear magnetic resonance (2D NMR) correlations mainly caused by high C/H ratios or proton-deficient and multiple heteroatoms through the conventional structural analytical methods. We reported a novel module-assembly calculation method named Dooerafa, which included constructing the meta-structures by a grafting method based on the crucial and the limited 2D NMR correlations, ring-contraction strategy based on mechanic force field and quantum chemical theory, and self-assemble calculation in Python programming for shaping up the structural candidates along with DFT-GIAO calculation. This new method, verified by a known alkaloid spiroreticulatine with the structure determined by X-ray diffraction, was performed for the structural elucidation of aaptourinamine isolated from marine sponge Aaptos suberitoides, showing us a brand new scaffold of imidazo [4,5,1-ij]pyrrolo [3,2-f]quinolin-7(8H)-one, which has a biosynthetic relationship with the bioactive and structurally unique aaptamine alkaloid.

Sarcoeleganolides C-G, Five New Cembranes from the South China Sea Soft Coral Sarcophyton elegans.

Five new cembranes, named sarcoeleganolides C-G (1-5), along with three known analogs (6-8) were isolated from soft coral Sarcophyton elegans collected from the Yagong Island, South China Sea. Their structures and absolute configurations were determined by extensive spectroscopic analysis, QM-NMR, and TDDFT-ECD calculations. In addition, compound 3 exhibited better anti-inflammation activity compared to the indomethacin as a positive control in zebrafish at 20 µM.

Chemical Constituents of the Seed Cake of Camellia oleifera and Their Antioxidant and Antimelanogenic Activities.

There is a growing interest in the exploitation of agricultural byproducts. This study explored the potential beneficial health effects from the main biowaste, tea seed pomace of Camellia oleifera Abel (Theaceae), produced when tea seed is processed. Eighteen compounds were isolated from the 70% EtOH extract of the seed cake of C. oleifera. Their structures were determined by ESI-MS, 1 H- and 13 C-NMR together with literature data. All fractions and compounds were evaluated for the antioxidant and melanogenesis inhibitory activities. As the result, AcOEt fraction has the best in vitro antioxidant and antimelanogenesis activities, compounds 7 - 12 and 15 showed remarkable antioxidant activity, compounds 4, 6, 8, and 15 - 17 exhibited superior inhibitory activities against melanogenesis. Furthermore, tyrosinase inhibitory activity assay suggested that compound 8 could suppress melanogenesis by inhibiting the expression of tyrosinase.

Typical structural characteristics and hepatoprotective effects of novel high Fischer ratio oligopeptides from Antarctic krill on acute alcoholic liver injury.

High Fischer ratio oligopeptides derived from Antarctic krill (HFOPs-AK) were screened, and their hepatoprotective effects and potential mechanisms were investigated. Herein, HFOPs-AK, with a Fischer ratio of 29 g/g (40.22 mol/mol) (MW < 1000 Da), were prepared via two-step enzymatic hydrolysis using chymotrypsin and flavourzyme and aromatic amino acid removal. Seventy-eight characteristic peptides were identified from HFOPs-AK through UHPLC-Q/TOF, with peptides containing Leu, Val, or Ile accounting for 79%. High hepatoprotective peptides were purified using GFC and RP-HPLC and identified as SDELGW and LLGWDDM. Furthermore, a murine model of acute liver injury induced by alcohol was successfully established. It was demonstrated that the oral administration of HFOPs-AK (800 mg per kg bw per d) remarkably increased the contents of ADH and ALDH compared with the model group, reaching 3.40 and 5.10 U mg-1 prot, respectively. Further, it was revealed that HFOPs-AK could effectively mitigate hepatic oxidative stress by increasing the levels of GSH-Px (p < 0.01) and decreasing the level of MDA (p < 0.05). Additionally, HFOPs-AK (800 mg per kg bw per d) attenuated liver inflammation by down-regulating the mRNA levels of TNF-α, IL-1ß, and IL-6 by 40.45%, 38.48%, and 35.83%, respectively. Therefore, HFOPs-AK may have the potential as a new nutritional supplement for the treatment of alcoholic liver injury.

Litoamentenes A-K, eleven undescribed cembranoids with cytotoxicity from the South China Sea soft coral Litophyton amentaceum.

Eleven undescribed cembrane-type diterpenoids, named litoamentenes A-K (1-11), were isolated from the soft coral Litophyton amentaceum collected from the South China Sea. Their structures were elucidated by extensive analysis of spectroscopic data, comparison with the literature data, single crystal X-ray diffraction, quantum chemical calculations and TDDFT-ECD calculations. This is the first systematic investigation of L. amentaceum. In particular, compounds 1-3 are cembrane-type norditerpenoids that lack isopropyl side chains. Compound 6 is a cembrane-type norditerpenoid without a methyl group at C-4, the first natural product identified with this carbon skeleton. Compounds 6, 9 and 10 showed modest cytotoxicity against several human cancer cell lines with IC50 values ranging from 3.99 to 14.56 µM.

Sarcoelegans A-H, eight undescribed cembranes with anti-inflammatory and anti-thrombotic activities from the South China Sea soft coral Sarcophyton elegans.

Chemical investigation of the South China Sea soft coral Sarcophyton elegans has led to the isolation of eight undescribed cembranes, namely sarcoelegans A-H. Their structures and absolute configurations were unambiguously established by extensive analyses of spectroscopic data, X-ray diffraction, QM-NMR, and TDDFT-ECD calculations. Sarcoelegan A is composed of the rare tricyclo [11.2.1.0] hexadecane carbon framework which is the third compound of this scaffold. Sarcoelegan B and sarcoelegan C possess an unusual seven-membered ether ring, and (±)-sarcoelegan D has a seven-membered ring with the rare peroxo bridge. In addition, sarcoelegan A, (±)-sarcoelegan D, sarcoelegan E, (+)-sarcoelegan F, and (+)-sarcoelegan H exhibited anti-inflammatory activity in zebrafish and sarcoelegan C exhibited anti-thrombotic activity in zebrafish.

Sarcoeleganolides H-K, new anti-thrombotic cembranes from soft coral Sarcophyton elegans.

Chemical investigation of soft coral the Sarcophyton elegans collected from the South China Sea led to the identification of four new cembranes, namely sarcoeleganolides H-K (1-4). Their structures and absolute configurations were established by 1D and 2D NMR spectroscopy, quantum chemical calculations of NMR chemical shifts and electronic circular dichroism (ECD) data analysis. Moreover, compound 2 exhibited moderate anti-thrombotic activity in zebrafish.

Two new spongian diterpene derivatives from the aquaculture sponge Spongia officinalis Linnaeus, 1759.

2ß,3α,19-Triacetoxy-17-hydroxyspongia-13(16),14-diene (1), a novel acetoxy diterpenoid, and 18-nor-2,17-hydroxyspongia-1,4,13(16),14-quaien-3-one (2), belonging to the rare 18-nor-spongian carbon skeleton, together with six related known metabolites (3‒8), were isolated from the aquaculture Spongia officinalis Linnaeus, 1759. Their structures were elucidated by comprehensive spectroscopic analysis, quantum chemical calculation of NMR parameters, and electronic circular dichroism (ECD). Compounds 3, 4, and 5 exhibited moderate inhibition against STAT3/NF-κB, HIF-1, Wnt signalling pathways. Compounds 1, 3, and 5 showed cytotoxicity activities against K562 cell line with IC50 values of 7.3, 3.5, and 6.4 µM, respectively.

Jellynolide A, pokepola esters, and sponalisolides from the aquaculture sponge Spongia officinalis L.

Jellynolide A, an unreported bicyclic diterpenoid with an unprecedented penta-substituted carbon skeleton which implied an irregular biogenic pathway, together with four pairs of rare phosphate triesters, (±)-pokepola ester B-E, one undescribed related racemic furanoterpenoid, (±)-sponalisolide C, one undescribed furanoterpenoid, (-)-sponalisolide D, and two known (±)-sponalisolide B and dendrolasin carboxylic acid were isolated from the aquaculture Spongia officinalis L. Their structures were elucidated by comprehensive spectroscopic analysis, quantum chemical calculation of NMR parameters, and electronic circular dichroism (ECD). The plausible biosynthetic pathway of jellynolide A was proposed. (±)-Pokepola ester C exhibited significant inhibition against Wnt, HIF1 signaling pathways. (+)-Pokepola ester B and (-)-pokepola ester D showed moderate cytotoxicity activities.

Sinudenoids A-E, C19-Norcembranoid Diterpenes with Unusual Scaffolds from the Soft Coral Sinularia densa.

Five new furanobutenolide-derived C19-norcembranoid diterpenes, sinudenoids A-E (1-5, respectively), were isolated from the soft coral Sinularia densa. Sinudenoid A (1) possesses an uncommon 5/5/11-fused tricyclic ring system. Sinudenoids B-D (2-4, respectively) share the same tetracyclic 5/5/6/6 ring system but represent two kinds of new skeletons. Sinudenoid E (5) is the second compound with the rare 8/8 bicyclic carbon core. A plausible biosynthesis pathway for compounds 1-6 is proposed. Compound 5 exhibits strong anti-inflammatory activity in the zebrafish model.