A chemical investigation of the endophyte Penicillium sp. (strain ZO-R1-1), isolated from roots of the medicinal plant Zingiber officinale, yielded nine new indole diterpenoids (1–9), together with 13 known congeners (10–22). The structures of the new compounds were elucidated by 1D and 2D NMR analysis in combination with HRESIMS data. The absolute configuration of the new natural products 1, 3, and 7 was determined using the TDDFT-ECD approach and confirmed for 1 by single-crystal X-ray determination through anomalous dispersion. The isolated compounds were tested for cytotoxicity against L5178Y, A2780, J82, and HEK-293 cell lines. Compound 1 was the most active metabolite toward L5178Y cells, with an IC50 value of 3.6 μM, and an IC50 against A2780 cells of 8.7 μM. Interestingly, 1 features a new type of indole diterpenoid scaffold with a rare 6/5/6/6/6/6/5 heterocyclic system bearing an aromatic ring C, which is suggested to be important for the cytotoxic activity of this natural product against L5278Y and A2780 cells.
Investigation of the sponge Clathria basilana collected in Indonesia afforded five new peptides, including microcionamides C (1) and D (2), gombamides B (4), C (5), and D (6), and an unusual amide, (E)-2-amino-3-methyl-N-styrylbutanamide (7), along with 11 known compounds, among them microcionamide A (3). The structures of the new compounds were elucidated by one- and two-dimensional NMR spectroscopy as well as by high-resolution mass spectrometry. The absolute configurations of the constituent amino acid residues in 1-7 were determined by Marfey's analysis. Microcionamides A, C, and D (1-3) showed in vitro cytotoxicity against lymphoma (Ramos) and leukemia cell lines (HL-60, Nomo-1, Jurkat J16), as well as against a human ovarian carcinoma cell line (A2780) with IC values ranging from 0.45 to 28 μM. Mechanistic studies showed that compounds 1-3 rapidly induce apoptotic cell death in Jurkat J16 and Ramos cells and that 1 and 2 potently block autophagy upon starvation conditions, thereby impairing pro-survival signaling of cancer cells. In addition, microcionamides C and A (1 and 3) inhibited bacterial growth of Staphylococcus aureus and Enterococcus faecium with minimal inhibitory concentrations between 6.2 and 12 μM. Mechanistic studies indicate dissipation of the bacterial membrane potential.
Marine organisms play an important role in natural product-based drug research due to accumulation of structurally unique and bioactive metabolites. The exploration of marine-derived compounds may significantly extend the scientific knowledge of potential scaffolds for antibiotic drug discovery. Development of novel antitubercular agents is especially significant as the emergence of drug-resistant Mycobacterium tuberculosis strains remains threateningly high. Marine invertebrates (i.e., sponges, corals, gorgonians) as a source of new chemical entities are the center of research for several scientific groups, and the wide spectrum of biological activities of marine-derived compounds encourages scientists to carry out investigations in the field of antibiotic research, including tuberculosis treatment. The present review covers published data on antitubercular natural products from marine invertebrates grouped according to their biogenetic origin. Studies on the structure-activity relationships of these important leads are highlighted as well.
Three new 2-methoxy acetylenic acids (1–3) and a known derivative (4), in addition to three new natural pyrazole alkaloids (5–7) were isolated from an Indonesian marine sponge of the genus Cinachyrella. Compounds 5 and 6 have previously been reported as synthetic compounds. The structures of the new compounds were established on the basis of one- and two-dimensional NMR spectroscopy as well as by mass spectrometric data. The absolute configuration of the new acetylenic acid derivatives (1–3) was established by ECD spectroscopy. All isolated compounds were evaluated for their cytotoxicity against L5178Y mouse lymphoma cells. Compounds 1–4 exhibited strong activity with an IC50 value of 0.3 µM. A plausible biosynthetic pathway for the pyrazole metabolites 5–7 is proposed.
The antibiotic resistance of phatogenic bacteria has become a serious health concern and encouragement to search for novel and efficient antimicrobial metabolites. On the other hand, endophytic fungi have great potential as a natural source for antimicrobial agents. The objective of this study was to isolate antibacterial compound from endophytic fungi A.elegans SweF9. The fungus was stationarily cultured at 30°C for 12 days in potato malt peptone (PMP) medium, then the filtrate was extracted with ethyl acetate. The antibacterial activities of the extract were evaluated by agar diffusion method against Gram-poitive (Bacillus subtilis and Staphylococcus aureus) and Gramnegative (Escherichia coli) bacterial strains. The broth extract at a concentration of 1% was able to inhibit the growth of E. coli, S. aureus and B. subtilis with an index of antibacterial activity 84.6%, 91.6%, and 90% compared to streptomycin sulfate at the same concentration. The active compound (1) was purified to yield amorphous white and identified using FTIR, NMR, and EI-MS analyses, revealed identified as (+)-epi-Epoformin. The compound showed an antibacterial activity index of against E. coli, S. aureus and B. subtilis bacterial were 48%, 45%, and 47%, respectively, at concentration 1%.
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