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The Red Sea is the home of a rich diversity of sponge species with unique ecological adaptations that thrive in its saline, warm, and nutrient-poor waters. Red Sea sponges offer potential as sources of bioactive compounds and novel drugs. The organic extract of the Red Sea sponge Agelas sp. aff. marmarica was investigated for its antimicrobial constituents. Through bioassay-guided fractionation of the antimicrobial fraction of the extract on SiO2 and Sephadex LH-20, as well as HPLC purification, three bioactive compounds, marmaricines A-C (1–3), were isolated. Structural elucidation of the compounds was performed using 1D (1H and 13C) and 2D (COSY, HSQC, HMBC, and NOESY) NMR, as well as (+)-HRESIMS, leading to the identification of the compounds. The antimicrobial activities of the compounds were assessed through evaluation of their inhibition zones, MIC, MBC, and MFC, against Methicillin-Resistant Staphylococcus aureus (MRSA), Escherichia coli, and Candida albicans. Marmaricines A and B exhibited the strongest antibacterial effects against MRSA, with inhibition zones ranging from 14.00 to 15.00 mm, MIC values of 8 µg/mL, and MBC values of 16 µg/mL. In comparison, marmaracine C showed slightly weaker activity (inhibition zone: 12 mm, MIC: 16 µg/mL, MBC: 32 µg/mL). In terms of antifungal activity, marmaricines B and C demonstrated the greatest effect against C. albicans, with inhibition zones of 14–15 mm, MIC values of 8 µg/mL, and MFCs of 16 µg/mL. Interestingly, none of the compounds showed any inhibitory effect against E. coli. The results indicate that marmaricines A-C are selectively active against MRSA, and marmaricines B and C demonstrate potential against C. albicans, making them promising candidates for the development of novel antimicrobial agents targeting resistant pathogens.

Pyrrole–imidazole alkaloids (PIAs) are a class of marine sponge derived natural products which have complex carbon frameworks and broad bioactivities. In this study, four new alkaloids, stylimassalins A–B (1–2), 3, and 5, together with two known compounds (4 and 6), were isolated from Stylissa massa. Compounds 2, 4, and 6 are the C-2 brominated analogues of 1, 3, and 5, respectively. Their structures display three different scaffolds, of which scaffold 1 (compounds 1,2) is new. A new biosynthetic pathway from oroidin, through spongiacidin, to latonduine and scaffold 1 was proposed by our group, in which the C12-N13-cleavaged compounds of spongiacidin (scaffold 2), dubbed seco-spongiacidins (3 and 4), are recognized as a key bridged scaffold, to afford PIA analogues (1,2 and 5,6). An anti-inflammatory evaluation in a zebrafish inflammation model induced by copper sulphate (CuSO4) demonstrated that stylimassalins A and B (1 and 2) could serve as a promising lead scaffold for treating inflammation.

Five new sulfated arylpyrrole and arylpyrrolone alkaloids, denigrins H–L (1–5), along with two known compounds, dictyodendrin B and denigrin G, were isolated from an extract of a New Zealand Dictyodendrilla c.f. dendyi marine sponge. Denigrins H–L represent the first examples of sulfated denigrins, with denigrins H and I (1–2), as derivatives of denigrin D, containing a pyrrolone core, and denigrins J–L (3–5), as derivatives of denigrin E (6), containing a pyrrole core. Their structures were elucidated by interpretation of 1D and 2D NMR spectroscopic data, ESI, and HR-ESI-MS spectrometric data, as well as comparison with literature data. Compounds 1–5, along with six known compounds previously isolated from the same extract, showed minimal cytotoxicity against the HeLa cervical cancer cell line.

Marine bacterium, strain MB30 isolated from the deep sea sediment of Bay of Bengal, India, exhibited antimicrobial activity against human pathogenic bacteria. Based on the 16S rRNA sequence homology and subsequent phylogenetic tree analysis, the strain MB30 was identified as Staphylococcus sp. The bioactive metabolite produced by the strain MB30 was purified through silica gel column chromatography and preparative HPLC. Purified metabolite was further characterized by FT-IR, LC–MS and NMR analyses. On the basis of spectroscopic data, the metabolite was identified as pyrrole (1, 2, a) pyrazine 1, 4, dione, hexahydro 3-(2-methyl propyl) (PPDHMP). The PPDHMP exhibited in vitro anticancer potential against lung (A549) and cervical (HeLa) cancer cells in a dose-dependent manner with the IC 50 concentration of 19.94 ± 1.23 and 16.73 ± 1.78 μg ml −1 respectively. The acridine orange (AO)/ethidium bromide (EB) and 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining of the IC 50 concentration of PPDHMP-treated cancer cells exhibited an array of morphological changes such as nuclear condensation, cell shrinkage and formation of apoptotic bodies. The PPDHMP-treated cancer cells induced the progressive accumulation of fragmented DNA in a time-dependent manner. Based on the flow cytometric analysis, it has become evident that the compound was also effective in arresting the cell cycle at G1 phase. Further, the Western blotting analysis confirmed the down-regulation of cyclin-D1, cyclin dependent kinase (CDK-2), anti-apoptotic Bcl-2 family proteins (Bcl-2 and Bcl-xL), activation of caspase-9 and 3 with the cleavage of PARP. The PPDHMP-treated cancer cells also showed the inhibition of migration and invasive capacity of cancer cells. In the present investigation, for the first time, we have reported the extraction, purification and characterization of an anticancer metabolite, PPDHMP from a new marine bacterium, Staphylococcus sp. strain MB30.

Tuberculosis remains a significant global health pandemic. There is an urgent need for new anti-tubercular agents to combat the rising incidence of drug resistance and to offer effective and additive therapeutic options. High-throughput screening of a subset of the NatureBank marine fraction library (n = 2000) identified a sample derived from an Australian marine sponge belonging to the order Haplosclerida that displayed promising anti-mycobacterial activity. Bioassay-guided fractionation of the organic extract from this Haplosclerida sponge led to the purification of previously identified antimicrobial pyrrole alkaloids, axinellamines A (1) and B (2). The axinellamine compounds were found to have a 90% minimum inhibitory concentration (MIC90) of 18 µM and 15 µM, respectively. The removal of protein and complex carbon sources reduced the MIC90 of 1 and 2 to 0.6 and 0.8 µM, respectively. The axinellamines were not toxic to mammalian cells at 25 µM and significantly reduced the intracellular bacterial load by >5-fold. These data demonstrate that axinellamines A and B are effective anti-tubercular agents and promising targets for future medicinal chemistry efforts.

Three new pyrrole alkaloids, streptopyrroles D–F (1–3), along with four known analogs (4–7) were isolated from Sea Anemone-Associated Streptomyces sp. S1502 via an OSMAC (One Strain Many Compounds)-based strategy. Their structures were elucidated through comprehensive spectroscopic analyses, including HRESIMS and 1D/2D NMR experiments (COSY, HSQC, and HMBC), and further confirmed by X-ray crystallography. Biological evaluation identified streptopyrrole (4) as an anti-MRSA (methicillin-resistant Staphylococcus aureus) agent, while 4 and 6 displayed broad-spectrum cytotoxicity and good selectivity against a panel of human cancer cell lines. Notably, 4 and 6 showed particularly potent activity against the lung cancer cell lines H1299, SW1573, and A549, with IC50 values ranging from 5.43 to 16.24 μM. Further mechanistic investigation revealed that both compounds suppress the proliferation of lung cancer cells by inducing cell cycle arrest at the G0/G1 phase and impair metastatic potential by inhibiting migration and invasion. These findings not only expand the structural diversity of marine-derived pyrrole alkaloids but also reveal the anticancer mechanisms of 4 and 6, highlighting their promise as active candidates for further antitumor drug development, particularly in lung cancer.

Stonikacidin A (1), the first representative of a new class of 4-bromopyrrole alkaloids containing an aldonic acid core, was isolated from the marine sponge Lissodendoryx papillosa. The compound is named in honor of Prof. Valentin A. Stonik, who is one of the outstanding investigators in the field of marine natural chemistry. The structure of 1 was determined using NMR, MS analysis, and chemical correlations. The L-idonic acid core was established by the comparison of GC, NMR, MS, and optical rotation data of methyl-pentaacetyl-aldonates obtained from the hydrolysis products of 1 and standard hexoses. The L-form of the idonic acid residue in 1 was confirmed by GC analysis of pentaacetate of (S)-2-butyl ester of the hydrolysis product from 1 and compared with corresponding derivatives of L- and D-idonic acids. The biosynthetic pathway for stonikacidin A (1) was proposed. The alkaloid 1 inhibited the growth of Staphylococcus aureus and Escherichia coli test strains, as well as affected the formation of S. aureus and E. coli biofilms. Compound 1 inhibited the activity of sortase A. Molecular docking data showed that stonikacidin A (1) can bind with sortase A due to the interactions between its bromine atoms and some amino acid residues of the enzyme.

Two new cyclized thiolopyrrolone derivatives, namely, thiolopyrrolone A (1) and 2,2-dioxidothiolutin (2), together with the kn own compound, thiolutin (3) were identified from a marine-derived Streptomyces sp. BTBU20218885, which was isolated from a mud sample collected from the coastal region of Xiamen, China. Their chemical structures were determined using spectroscopic data, including HRESIMS, 1D and 2D NMR techniques. 1 possessed a unique unsymmetrical sulfur-containing thiolopyrrolone structure. All the compounds were tested for bioactivities against Staphylococcus aureus, Escherichia coli, Bacille Calmette–Guérin (BCG), Mycobacterium tuberculosis, and Candida albicans. 1 displayed antibacterial activities against BCG, M. tuberculosis, and S. aureus with minimum inhibitory concentration (MIC) values of 10, 10, and 100 μg/mL, respectively. Thiolutin (3) showed antibacterial activities against E. coli, BCG, M. tuberculosis, and S. aureus with MIC values of 6.25, 0.3125, 0.625, and 3.125 μg/mL, respectively.

Three pyrrole alkaloid derivatives were isolated from the edible mushroom Basidiomycetes-X (Echigoshirayukidake) by water extraction followed by ethyl acetate fractionation. The chemical structures determined by MS and NMR were 4-[2-formyl-5-(hydroxymethyl)-1H-pyrrol-1-yl] butanoic acid (compound I), 4-[2-formyl-5-(hydroxymethyl)-1H-pyrrol-1-yl] butanamide (compound II), and 5-(hydroxymethyl)-1H-pyrrole-2-carboxaldehyde (compound III). Compound I was found to be the major component, followed by compound II, and compound III was the minor component. The dry powder of Basidiomycetes-X contained approximately 825 μg g−1 compound I and 484 μg g−1 compound II. Compound II was found to be a novel pyrrole aldehyde homologue not previously reported and thus is a specific component of this mushroom.

Annona muricata Linn or usually identified as soursop is a potential anticancer plant that has been widely reported to contain valuable chemopreventive agents known as annonaceous acetogenins. The antiproliferative and anticancer activities of this tropical and subtropical plant have been demonstrated in cell culture and animal studies. A. muricata L. exerts inhibition against numerous types of cancer cells, involving multiple mechanism of actions such as apoptosis, a programmed cell death that are mainly regulated by Bcl-2 family of proteins. Nonetheless, the binding mode and the molecular interactions of the plant’s bioactive constituents have not yet been unveiled for most of these mechanisms. In the current study, we aim to elucidate the binding interaction of ten bioactive phytochemicals of A. muricata L. to three Bcl-2 family of antiapoptotic proteins viz. Bcl-2, Bcl-w and Mcl-1 using an in silico molecular docking analysis software, Autodock 4.2. The stability of the complex with highest affinity was evaluated using MD simulation. We compared the docking analysis of these substances with pre-clinical Bcl-2 inhibitor namely obatoclax. The study identified the potential chemopreventive agent among the bioactive compounds. We also characterized the important interacting residues of protein targets which involve in the binding interaction. Results displayed that anonaine, a benzylisoquinoline alkaloid, showed a high affinity towards the Bcl-2, thus indicating that this compound is a potent inhibitor of the Bcl-2 antiapoptotic family of proteins.