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Antibacterial resistance is a serious threat against humankind and the search for new therapeutics is needed. This study aims to investigate the antibacterial activity of extracts and compounds from Echinops gracilis O. Hoffm. Standard chromatographic and spectroscopic methods were used to isolate and characterize compounds ( 1-15 ) from the methanol extract. The extract, chromatographic fractions and compounds 1-3 , 8 , 11 , 13 and 14 were subjected to in vitro antibacterial assays against Staphylococcus aureus ATCC25923 , Salmonella Typhi ATCC6539, Klebsiella pneumoniae 22, and Salmonella Typhi 68, using broth micro-dilution method. As results, a new nor-triterpenoid ( 1 ) and fourteen known compounds ( 2-15 ) were characterized. The extract and fractions displayed moderate (128 ≤ MIC ≤ 512 μg/mL) and significant (MIC 64 μg/mL) antibacterial activities. Compounds 1 and 14 showed the best anti-staphylococcal and anti-salmonella activity (MIC 16 µg/mL), respectively. These results partially justified the antimicrobial uses of E. gracilis in traditional medicine.

Two new stigmastane steroids ( 1 and 2 ) were isolated from the methanol extract of the leaves of Vernonia glabra , together with seventeen known compounds ( 3-19 ) including one fatty acid, four triterpenoids, four steroids, one trinitropropanoyl glucoside, and seven flavonoids. The structures of compounds 1 and 2 were assigned based on their IR, NMR and MS data, and by comparison with literature values. The MeOH extract, its fractions and isolated compounds were subjected to in vitro antibacterial assay against two Gram-positive ( Staphylococcus aureus ATCC25923 and Streptococcus pneumoniae ATCC49619) and two Gram-negative ( Escherichia coli ATCC8739 and Klebsiella pneumoniae ATCC10031) bacteria, using broth microdilution method. The extract and fractions exhibited (16 ≤ MIC ≤ 512 μg/mL) antibacterial activities. The isolated and tested compounds were also active (16 ≤ MIC ≤ 128 μg/mL) against the four pathogenic bacteria, with compound 2 being the most active and E. coli , the most sensitive microorganism.

A phytochemical study of the methanol extract of the fruit of Maesa lanceolata resulted in the isolation of a new alkenylbenzoquinone ( 1 ), alongside the known compounds ( Z )-2,5-dihydroxy-6-methyl-3-(pentadec-10'-enyl)-1,4-benzoquinone ( 2 ), 2,5-dihydroxy-6-methyl-3-(nonadec-14'-enyl)-1,4-benzoquinone ( 3 ), 2,5-dihydroxy-6-methyl-3-(tridecyl)-1,4-benzoquinone ( 4 ), (2 S ,3 S ,4 R ,2' R ,9E)-[2'-hydroxytetraeicosanoyl]-2-aminooctadec-9-ene-1,3,4-triol ( 5 ), monopalmitin (glyceryl palmitate) ( 6 ), lupeol ( 7 ), and 3- O -( β -D-glucopyranoside)- β -sitosterol ( 8 ). The structures of the compounds were established by the means of spectroscopic (1 D- and 2 D-NMR) and spectrometric techniques (MS). The isolated compounds were assessed for their antibacterial, cytotoxic, and antiradical activities. Compound 2 showed moderate activity against Staphylococcus warneri (DSMZ 20036), while the other compounds were inactive. The two quinones 1 and 2 were significantly cytotoxic, with IC 50 values of 0.005  µ M and 12.5  µ M respectively, and were weakly active towards DPPH radical (IC 50 >250  µ g/mL).