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.

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Analysis of an antimicrobial extract prepared from culture broth of the marine-derived actinomycete Nocardiopsis sp. (strain G057) led to the isolation of twelve compounds, 1-12. Compound 1 (2-[(2R-hydroxypropanoyl)amino]benzamide) was found to be a new enantiomeric isomer while compounds 2 (3-acetyl-4-hydroxycinnoline) and 3 (3,3'-bis-indole) were isolated from a natural source for the first time. The structures of 1-12 were determined by analyses of MS and 2D NMR data. All compounds were evaluated for their antimicrobial activity against a panel of clinically significant microorganisms. Compound 1 selectively inhibited Escherichia coli (MIC: 16 µg/mL). Compounds 2 and 3 exhibited antimicrobial activity against several strains of both Gram-positive and Gram-negative bacteria, and the yeast Candida albicans. Cytotoxic evaluation of compounds 1-3 against four cancer cell lines (KB, LU-1, HepG-2 and MCF-7) indicated that compound 3 produced a weak inhibition against KB and LU cell lines. Two remaining compounds, 1 and 2 were not cytotoxic, even at the concentration of 128 μg/mL.

Two new compounds, a quinoline alkaloid (1) and a 1,4-dioxane derivative (2), were isolated from culture broth of the marine-derived actinomycete Micromonospora sp. (strain G019) by bioassay-guided fractionation. This actinomycete strain was isolated from sediment, collected at Cát Bà Peninsula, Vietnam. The taxonomic identification was achieved by analysis of 16S rRNA gene sequences. On the basis of morphological and phylogenetic evidence, strain G019 was assigned to the genus Micromonospora. The structures of 1 and 2 were established by spectroscopic data analysis, including one-and two-dimensional NMR, and MS. Compound 1 was found to have antibacterial activity against Escherichia coli (MIC: 48 µg/mL), Salmonella enterica (MIC: 96 µg/mL) and Enterococcus faecalis (MIC: 128 µg/mL), while compound 2 showed inhibitory activity against Enterococcus faecalis (MIC: 32 µg/mL) and Candida albicans (MIC: 64 µg/mL).

Analysis of an antimicrobial extract from the culture broth of the marine-derived actinomycete Streptomyces sp. G261 led to the isolation of a new 1,3-benzodioxole derivative (1), together with 10 known compounds 2-11. The actinomycete strain G261 was isolated from sediment, collected at Cu Lao Cham, Quang Nam in Vietnam. The taxonomic identification of the strain G261 was achieved by analysis of 16SrRNA gene sequences. On the basis of morphological and phylogenetic evidence, the actinomycete strain G261 was assigned to the genus Streptomyces. The structures of the isolated compounds were established by their spectral data analysis, including mass spectrometry, 1-dimensional nuclear magnetic resonance (1D-NMR), and 2D-NMR. The structure of 1 was confirmed by comparison of the calculated with experimental 13C NMR data. Compound 1 exhibited antimicrobial activity against Enterococcus faecalis and Staphylococcus aureus with minimum inhibitory concentration values of 128 and 256 µg/mL, respectively. Whereas, compound 1 had a weak inhibition when tested against 4 cancer cell lines, KB, LU-1, HepG-2, and MCF-7.