Coculture is a productive technique to trigger microbes’ biosynthetic capacity by mimicking the natural habitats’ features principally by competition for food and space and interspecies cross-talks. Mixed cultivation of two Red Sea-derived actinobacteria, Actinokineospora spheciospongiae strain EG49 and Rhodococcus sp. UR59, resulted in the induction of several non-traced metabolites in their axenic cultures, which were detected using LC–HRMS metabolomics analysis. Antimalarial guided isolation of the cocultured fermentation led to the isolation of the angucyclines actinosporins E (1), H (2), G (3), tetragulol (5) and the anthraquinone capillasterquinone B (6), which were not reported under axenic conditions. Interestingly, actinosporins were previously induced when the axenic culture of the Actinokineospora spheciospongiae strain EG49 was treated with signalling molecule N-acetyl-d-glucosamine (GluNAc); this finding confirmed the effectiveness of coculture in the discovery of microbial metabolites yet to be discovered in the axenic fermentation with the potential that could be comparable to adding chemical signalling molecules in the fermentation flask. The isolated angucycline and anthraquinone compounds exhibited in vitro antimalarial activity and good biding affinity against lysyl-tRNA synthetase (PfKRS1), highlighting their potential developability as new antimalarial structural motif.
A new collection of several Red Sea sponges was investigated for the discovery of potential breast cancer migration inhibitors. Extracts of the Verongid sponges Pseudoceratina arabica and Suberea mollis were selected. Bioassay-directed fractionation of both sponges, using the wound-healing assay, resulted into the isolation of several new and known brominated alkaloids. Active fractions of the sponge Pseudoceratina arabica afforded five new alkaloids, ceratinines A–E (2–6), together with the known alkaloids moloka’iamine (1), hydroxymoloka’iamine (7) and moloka’iakitamide (8). The active fraction of the sponge Suberea mollis afforded the three known alkaloids subereamolline A (9), aerothionin (10) and homoaerothionin (11). Ceratinine B (3) possesses an unprecedented 5,7-dibrominated dihydroindole moiety with an epoxy ring on the side chain of a fully substituted aromatic moiety. Ceratinines D (5) and E (6) possess a terminal formamide moiety at the ethylamine side chain. Subereamolline A (9) potently inhibited the migration and invasion of the highly metastatic human breast cancer cells MDA-MB-231 at the nanomolar doses. Subereamolline A and related brominated alkaloids are novel scaffolds appropriate for further future use for the control of metastatic breast cancer.
A novel phenanthrenoid symmetrical dimer 8,8'-bidehydrojuncusol [1,1',6,6'-tetramethyl-5,5'-divinyl-8,8'-biphenanthrene-2,2',7,7'-tetraol], a related phenanthrenoid monomer, a phenolic chromone, and five flavonoids derivatives have been isolated from the halophyte Juncus acutus L., Juncaceae. The structure of the dimeric phenanthrenoid was determined on the basis of spectroscopic analyses, including 2D NMR spectroscopy, and by spectral correlations. The new dimer and the other isolated compounds bearing four phenolic hydroxy groups showed the significant in vitro antioxidant activity comparable with that of ascorbic acid using 2,2'-azino-bis[3-ethylbenzothiazoline-6-sulphonate] (ABTS) radical cation decolourisation assay. On the basis of the results from an in vitro anti-inflammatory assay using lipopolysaccharide-stimulated RAW264.7 macrophage cells linked with immunoblot analysis, it was found that dimerisation of dehydrojuncusol [1,6-dimethyl-5-vinyl-8-phenanthrene-2,7-diol] molecule nearly nullified its inhibitory effect on the expression of the pro-inflammatory inducible nitric oxide synthase (iNOS) protein.
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