Three new lavandulylated flavonoids, (2S,2″S)-6-lavandulyl-7,4′-dimethoxy-5,2′-dihydroxylflavanone (1), (2S,2″S)-6-lavandulyl-5,7,2′,4′-tetrahydroxylflavanone (2), and (2″S)-5′-lavandulyl-2′-methoxy-2,4,4′,6′-tetrahydroxylchalcone (3), along with seven known compounds 4–10 were isolated from culture broth of Streptomyces sp. G248. Their structures were established by spectroscopic data analysis, including 1D and 2D nuclear magnetic resonance (NMR), and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The absolute configurations of 1–3 were resolved by comparison of their experimental and calculated electronic circular dichroism spectra. Compounds 1–3 exhibited remarkable antimicrobial activity. Whereas, two known compounds 4 and 5 exhibited inhibitory activity against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) values of 6.0 µg/mL and 11.1 µg/mL, respectively.

Marine microorganisms are an invaluable source of novel active secondary metabolites possessing various biological activities. In this study, the extraction and isolation of the marine sediment Penicillium species collected in Vietnam yielded ten secondary metabolites, including sporogen AO-1 (1), 3-indolecarbaldehyde (2), 2-[(5-methyl-1,4-dioxan-2-yl)methoxy]ethanol (3), 2-[(2R-hydroxypropanoyl)amino]benzamide (4), 4-hydroxybenzandehyde (5), chrysogine (6), 3-acetyl-4-hydroxycinnoline (7), acid 1H-indole-3-acetic (8), cyclo (Tyr-Trp) (9), and 2’,3’-dihydrosorbicillin (10). Their structures were identified by the analysis of 1D and 2D NMR data. Among the isolated compounds, 2-[(5-methyl-1,4-dioxan-2-yl)methoxy]ethanol (3) showed a strong inhibitory effect against Enterococcus faecalis with a minimum inhibitory concentration value of 32 µg/mL. Both 2-[(2R-hydroxypropanoyl)amino]benzamide (4) and 4-hydroxybenzandehyde (5) selectively inhibited E. coli with minimum inhibitory concentration values of 16 and 8 µg/mL, respectively. 2’,3’-Dihydrosorbicillin (10) potentially inhibited α-glucosidase activity at a concentration of 2.0 mM (66.31%).

Analysis of an antimicrobial extract prepared from culture broth of the marine-derived actinomycete Streptomyces sp. G278 led to the isolation of ten compounds, 1-10. Two compounds, 2,5-Bis(5-tert-butyl-2-benzoxazolyl)thiophene (1), and 3-hydroxyl-2-methylpyridine (2) were isolated from a natural source for the first time. The structures of the isolated compounds were established by their spectral data analysis, including mass spectrometry, 1D-NMR, 2D-NMR, and X-ray crystallographic analysis in case of compound 3. All isolated compounds were evaluated for their antimicrobial activity against a panel of clinically significant microorganisms. Compounds 1 and 3 selectively inhibited Enterococcus faecalis (MIC: 256 μg/mL). Compound 2 was found to have antibacterial and antifungal activity against Escherichia coli (MIC: 64 μg/mL), Salmonella enterica (MIC: 256 μg/mL), Staphylococcus aureus (MIC: 256 μg/mL), Enterococcus faecalis (MIC: 256 μg/mL), and Candida albicans (MIC: 64 μg/mL). Except for compounds 9 and 10, the other known metabolites (4-8) also exhibited antimicrobial activity.

Two new prenylated flavonoids, 4´-methyl-8-prenyltaxifolin (1) and 6,8-diprenyl-4´-methyl-naringenin (2) and a new geranylated stilbene, 4′-deprenyl-4-methoxymappain (3) together with eight known flavonoids (4–11) were isolated from the fruits of Macaranga balansae Gagnep. Their chemical structures were determined by means of spectroscopic methods including 1D, 2D NMR, and MS data. Compound 2 showed the highest cytotoxic activity against PanC1, A549, KB and LU-1 cell lines with IC₅₀ values range from 7.89 to 22.81 µM.

Four new prenylated flavonoids, macarindicins I-IV (1-4) together with ten known compounds, broussoflavonol F (5), vedelianin (6), schweinfurthin E (7), vitexin (8), 2″-rhamnosyl vitexin (9), isovitexin (10), (6R,7E,9R)-9-hydroxy-megastigman-4,7-dien-3-one-9-O-β-D-glucopyranoside (11), 6S,9R)-roseoside (12), (6S,9S)-roseoside (13), and bridelionoside B (14) were isolated from the leaves of Macaranga indica. Their structures were determined on the basis of extensive spectroscopic methods, including 1D-, 2D-NMR, and MS data. All the isolated compounds were evaluated for their cytotoxic activities against four human cancer cell lines including KB, MCF-7, HepG-2, and LU. As a result, compound 6 significantly exhibited cytotoxic activity against all tested human cancer cell lines with IC₅₀ values ranging from 4.7 to 11.0 μM. Compounds 2, 5, and 7 showed moderate cytotoxic activity with IC₅₀ values ranging from 7.0 to 38.7 μM.