Seven new 14-membered macrolides, pestalotioprolides C (2), D-H (4-8), and 7-O-methylnigrosporolide (3), together with four known analogues, pestalotioprolide B (1), seiricuprolide (9), nigrosporolide (10), and 4,7-dihydroxy-13-tetradeca-2,5,8-trienolide (11), were isolated from the mangrove-derived endophytic fungus Pestalotiopsis microspora. Their structures were elucidated by analysis of NMR and MS data and by comparison with literature data. Single-crystal X-ray diffraction analysis was used to confirm the absolute configurations of 1, 2, and 10, while Mosher's method and the TDDFT-ECD approach were applied to determine the absolute configurations of 5 and 6. Compounds 3-6 showed significant cytotoxicity against the murine lymphoma cell line L5178Y with IC50 values of 0.7, 5.6, 3.4, and 3.9 μM, respectively, while compound 5 showed potent activity against the human ovarian cancer cell line A2780 with an IC50 value of 1.2 μM. Structure-activity relationships are discussed. Coculture of P. microspora with Streptomyces lividans caused a roughly 10-fold enhanced accumulation of compounds 5 and 6 compared to axenic fungal control.

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The cyclic depsipeptide FR900359 (FR), isolated from the traditional Chinese medicine plant Ardisia crenata, is a potent Gq protein inhibitor and thus a valuable tool to study Gq-mediated signaling of G protein-coupled receptors. Two new FR analogues (3 and 4) were isolated from A. crenata together with the known analogues 1 and 2. The structures of compounds 3 and 4 were established by NMR spectroscopic data and MS-based molecular networking followed by in-depth LCMS analysis. The latter approach led to the annotation of further FR analogues 5-9. Comparative bioactivity tests of compounds 1-4 along with the parent molecule FR showed high-affinity binding to Gq proteins in the low nanomolar range (IC = 2.3-16.8 nM) for all analogues as well as equipotent inhibition of Gq signaling, which gives important SAR insights into this valuable natural product. Additionally, FR was detected from leaves of five other Ardisia species, among them the non-nodulated leaves of Ardisia lucida, implying a much broader distribution of FR than originally anticipated.

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A new pregnanone, named calotropone (1), was isolated from the EtOH extract of the roots of Calotropis gigantea L. together with a known cardiac glycoside. The structures were elucidated by a study of their physical and spectral data. Compounds 1 and 2 displayed inhibitory effects towards chronic myelogenous leukemia K562 and human gastric cancer SGC-7901 cell lines.

Along with five known 30-norlanostane-type saponins, sarasinosides A(1) (5A), A3 (6A), I1 (7), I2 (8), and H2 (9), four new triterpenoidal saponin congeners, sarasinosides J (1), K (2), L (3), and M (4), were isolated from the Indonesian sponge Melophlus sarassinorum. Sarasinosides J (1) and K (2) are the 24,25-hydrogenated congeners of the previously described sarasinosides A1 and H2, respectively. The carbon skeleton of sarasinoside M (4) possesses a rearranged 8alpha,9alpha-epoxy-8,9-seconorlanosta-8(14),9(11),24-triene system, which is novel and unprecedented in nature. The structures of the new compounds were confirmed by spectral analyses, chemical derivatization, and GC analyses. Compounds 1 and 5A exhibited antimicrobial activity toward Bacillus subtilis and Saccharomyces cerevisiae.

Chemical investigation of the ethyl acetate extract of Corynespora cassiicola, isolated from leaf tissues of the Chinese mangrove medicinal plant Laguncularia racemosa, yielded four new secondary metabolites, including three decalactones, xestodecalactones D–F (1–3) as well as corynesidone C (4), in addition to four known compounds. The structures of the new compounds were determined on the basis of one‐ and two‐dimensional NMR spectroscopy as well as by high‐resolution mass spectrometry. Absolute configurations of the optically active compounds 1–3 were determined by TDDFT ECD calculations of their solution conformers, proving that they belong to the (11S) series of xestodecalactones, opposite to the (11R) configuration of the known xestodecalactones A–C. All compounds were tested against a panel of human protein kinases. Among the isolated compounds, two inhibited several kinases such as IGF1‐R and VEGF‐R2 with IC50 values mostly in the low micromolar range.

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