Absolute configuration of polypropionate derivatives: Decempyrones A-J and their MptpA inhibition and anti-inflammatory activities

Four new diterpenoids from the aerial parts of Leucas zeylanica (L.) R. Br

Four new undescribed halimane- and labdane-type diterpenoids, named zeylleucapenoids E-H (1-4), along with four known analogues (5-8), were isolated from the aerial parts of Leucas zeylanica (L.) R. Br. Their structures were determined by comprehensive spectroscopic analysis and computational calculations. Compounds 1 and 2 are the highly modified halimane diterpenoids featuring a 6/6/6-fused tricyclic system with an unusual six-membered 6,11-ether ring. Compound 8 exhibits nontoxic effects for zebrafish embryo, while it displays efficient reduction against NO production in a dose-dependent manner and strongly suppresses the secretion of LPS-induced TNF-α and IL-6 cytokines in RAW264.7 macrophages. In addition, marked reductions of iNOS and COX-2 expression were observed. Molecular docking analysis indicated that 8 has high affinities with the target amino acid residues on protein-binding sites, which may be a possible mechanism contributing to the anti-inflammatory potential of this molecule.

Plumeriapropionics A-E, Carboxyl-Substituted Phenylpropionic Acid Derivatives with Anti-Inflammatory Activity from Plumeria rubra L

Five rare carboxyl-substituted phenylpropionic acid derivatives, plumeriapropionics A-E (1-5), together with one known analog, cerberic acid B (6), were isolated from flowers of Plumeria rubra L. Their structures were elucidated using comprehensive spectroscopic methods. To date, only one compound of this structural type has been reported. The inhibitory activities of compounds 1-6 against nitric oxide (NO) production induced by lipopolysaccharide (LPS) were evaluated in vitro using mouse macrophage RAW264.7 cells. Compounds 1-6 showed remarkable inhibitory activities on NO production, with IC50 values in the range of 6.52 ± 0.23 to 35.68 ± 0.17 µM. These results indicate that the discovery of carboxyl-substituted phenylpropionic acid derivatives from the flowers of P. rubra, which show significant anti-inflammatory properties, could be of great importance for the research and development of novel natural anti-inflammatory agents.

Cyclohexenoneterpenes A-J: Cytotoxic meroterpenoids from mangrove-associated fungus Penicillium sp. N-5

Ten previously undescribed meroterpenoids, cyclohexenoneterpenes A-J (1-7, 18-20), together with 10 known analogues (8-17) were isolated from the mangrove-associated fungus Penicillium sp. N-5. Their structures were elucidated on the basis of extensive spectroscopic and mass spectrometric data. The absolute configurations of the undescribed compounds were assigned by electronic circular dichroism calculations, the modified Mosher's method, NMR calculations and DP4+ analysis. In the bioassay, compounds 10, 11, 15, and 20 exhibited cytotoxicities against SNB-19, MDA-MB-231, MDA-MB-435 and HCT-116 cell lines with IC50 values ranging from 1.4 to 19.1 μM.

Anti-inflammatory acetylenic meroterpenoids from the ascidian-derived fungus Amphichorda felina SYSU-MS7908

A combination strategy of 13C NMR and bioinformatics was established to expedite the discovery of acetylenic meroterpenoids from the ascidian-derived fungus Amphichorda felina SYSU-MS7908. This approach led to the identification of 13 acetylenic meroterpenoids (1-13) and four biogenic analogs (14-17), including five new ones named felinoids A-E (1-4 and 15). Their structures and absolute configurations were elucidated using extensive spectroscopy, ECD quantum chemical calculations, and single-crystal X-ray diffraction analysis. Compound 1 possessed a rare cyclic carbonate in natural acetylenic meroterpenoids. The plausible shikimate-terpenoid biosynthetic pathways of 1-4 were also postulated. Five of these isolates exhibited anti-inflammatory activity by inhibiting NO production in LPS-induced RAW264.7 cells (IC50 = 11.6-19.5 μM). Moreover, oxirapentyn E diacetate showed a dose-dependent inhibition of pro-inflammatory cytokines IL-6 and TNF-α. Structural modification of oxirapentyn B yielded 29 new derivatives, among which seven showed improved activity (IC50 < 3 μM) and higher selectivity index (SI > 22). The structure-activity relationship study indicated that 7, 8-epoxy, and 6-acylation were crucial for the activity. These findings may provide a powerful tool to accelerate the discovery of new fungal acetylenic meroterpenoids for future anti-inflammatory drug development.

Zeylleucapenoids A-D, Highly Oxygenated Diterpenoids with Anti-Inflammatory Activity from Leucas zeylanica (L.) R. Br

Four previously undescribed highly oxygenated diterpenoids (1-4), zeylleucapenoids A-D, characterized by halimane and labdane skeletons, were isolated from the aerial parts of Leucas zeylanica. Their structures were elucidated primarily via NMR experiments. The absolute configuration of 1 was established using theoretical ECD calculations and X-ray crystallographic analysis, whereas those for 2-4 were assigned using theoretical ORD calculations. Zeylleucapenoids A-D were tested for anti-inflammatory activity against nitric oxide (NO) production in RAW264.7 macrophages, of which only 4 showed significant efficacy with an IC₅₀ value of 38.45 μM. Further, active compound 4 was also evaluated for the inhibition of the release of pro-inflammatory cytokines TNF-α and IL-6 and was found to have a dose-dependent inhibitory effect, while it showed nontoxic activity for zebrafish embryos. A subsequent Western blotting experiment revealed that 4 inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, molecular docking analysis indicated that the possible mechanism of action for 4 may be bind to targets via hydrogen and hydrophobic bond interactions.

Absolute configuration of cyclopropanes and the structural revision of pyrones from Marine-derived fungus Stagonospora sp. SYSU-MS7888

Two new cyclopropane derivatives (1-2) and seven undescribed α-pyrone derivatives (3-9), along with one known congener (10) were obtained from the marine fungus Stagonospora sp. SYSU-MS7888, which was isolated from the South China Sea. Their planar structures were established through extensive spectroscopic analyses including 1D and 2D NMR and HR-ESIMS. The absolute configurations were identified on basis of the quantum chemical calculations of ECD and NMR, as well as the modified Mosher's method. It's particularly noteworthy that the tetrasubstituted furopyrans, chenopodolans A-F, possessing phytotoxicity and zootoxicity, were structural misassignments. The structures of chenopodolans featuring with furopyran skeleton were revised as common trisubstituted α-pyrones by computational chemistry, NMR spectroscopic method, and empirical rule. Compounds 1, 2, 7, and 9 showed significant anti-inflammatory activity with IC₅₀ values ranging from 3.6 to 22.8 μM, which is better than the positive control indomethacin (IC₅₀ = 26.5 ± 1.13 μM). This discovery holds potential for the development of new anti-inflammatory agents.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) 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 (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

Secondary metabolites from the Endophytic fungi Fusarium decemcellulare F25 and their antifungal activities

Seven new compounds, including three isocoumarins (1-3), three pyrrolidinone derivatives (8-10), and one pentaene diacid (15), together with 13 known compounds, were isolated from the rice culture of the endophytic fungus Fusarium decemcellulare F25. Their structures and stereochemistry were established using HRESIMS, NMR, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction. The possible biosynthetic pathways for compounds 1-3 and 8-10 were proposed. The antifungal efficacies of compounds 1 - 20 were evaluated against Colletotrichum musae, and compounds 13, 14, and 17 exhibited inhibitory activities against C. musae with MIC values of 256, 64 and 128 μg/mL, respectively.

Targeted Discovery of Sorbicillinoid Pigments with Anti-Inflammatory Activity from the Sponge-Derived Fungus Stagonospora sp. SYSU-MS7888 Using the PMG Strategy

An effective identification and discovery of fungal pigments is very important to illustrate the role of fungal pigments in the life process and conduce to the discovery of new bioactive and edible pigments. The phenotype combined with metabolomic and genomic (PMG) strategy led to the discovery and characterization of three new sorbicillinoid pigments, stasorbicillinoids A-C (1-3), and five known analogues (4-8) from the sponge-derived fungus Stagonospora sp. SYSU-MS7888. Their structures were elucidated by the application of spectroscopic methods (NMR, MS, UV, IR, and ECD) and modified Mosher's method. Compounds 1 and 2 featured novel naphthone nuclei linked by two alkyl side chains possibly undergoing inter- and intramolecular Michael reactions. Compounds 1-8 exhibited potent anti-inflammatory activity with IC₅₀ values in the range of 3.56-22.8 μM. Furthermore, compound 2 inhibited the production of IL-1β, IL-6, and TNF-α in a dose-dependent manner. This study provides an effective strategy to accelerate the discovery of new fungal pigments and further exploration of their potential applications in different fields such as medicine and food industries.

Bioactive Monoterpenes and Polyketides from the Ascidian-Derived Fungus Diaporthe sp. SYSU-MS4722

There has been a tremendous increase in the rate of new terpenoids from marine-derived fungi being discovered, while new monoterpenes were rarely isolated from marine-derived fungi in the past two decades. Three new monoterpenes, diaporterpenes A–C (1–3), and one new α-pyrones, diaporpyrone A (6), along with nine known polyketides 4, 5, and 7–13 were isolated from the ascidian-derived fungus Diaporthe sp. SYSU-MS4722. Their planar structures were elucidated based on extensive spectroscopic analyses (1D and 2D NMR and HR-ESIMS). The absolute configurations of 1 and 3 were identified by an X-ray crystallographic diffraction experiment using Cu-Ka radiation, and those of compound 2 were assigned by calculating NMR chemical shifts and ECD spectra. It afforded an example of natural epimers with different physical properties, especially crystallization, due to the difference in intermolecular hydrogen bonding. Compounds 9, 10, and 13 showed moderate total antioxidant capacity (0.82 of 9; 0.70 of 10; 0.48 of 13) with Trolox (total antioxidant capacity: 1.0) as a positive control, and compounds 5 and 7 showed anti-inflammatory activity with IC₅₀ values of 35.4 and 40.8 µM, respectively (positive control indomethacin: IC₅₀ = 35.8 µM).