Chemical constituents from the leaves of Sindora siamensis var. maritima and their antimicrobial and α-glucosidase inhibitory activities.

Two new glycosides, sindosides A-B (1-2), along with 11 previously identified metabolites (3-13), were isolated from an ethanolic extract of the leaves of Sindora siamensis var. maritima. The structures of the purified phytochemicals were elucidated by interpreting their spectroscopic data (IR, NMR, and HRMS). The absolute configuration of compound 1 was established by experimental and calculated ECD spectra. The antimicrobial results revealed that compound 8 selectively inhibited C. albicans fungal with a MIC value of 64 µg/mL, whereas 11 presented a weak inhibition toward E. faecalis, S. aureus, and B. cereus bacterial strains with the same MIC value of 128 µg/mL. Interestingly, compounds 1, 2, 8, 9, and 11 showed α-glucosidase inhibitory activity with IC50 values ranging from 14.42 ± 0.21 to 30.62 ± 0.18 µM, which were more active than the positive control (acarbose, with an IC50 value of 46.78 ± 1.37 µM). Enzyme kinetic analysis revealed that compounds 1, 2, and 11 behaved as uncompetitive inhibitors with Ki values of 8.60 ± 1.04, 5.16 ± 0.73, and 7.17 ± 0.98 µM, respectively.

Antimicrobial constituents from the leaves of Hibiscus tiliaceus L.

Repeated column chromatography resulted in the isolation of two new megastigmane derivatives, methyl-tiliaceates A and B (1 and 2), along with four known metabolites (3-6) from the leaves of Hibiscus tiliaceus L. The structures of the purified phytochemicals were elucidated by interpreting their NMR, HRESIMS, and CD spectroscopic data, as well as comparison with the previous literature. The compounds isolated were subjected to in vitro antimicrobial assays against a panel of pathogenic microorganisms (Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans). Compound 1 showed obvious selective inhibition against the B. cereus strain, whereas 3 - 5 showed weak inhibitory activities against E. faecalis and S. aureus bacterial, and C. albicans fungal strains (with MIC values ranging from 128 to 256 µg/mL).

Glycoside constituents from Miliusa sinensis leaves and their anti-inflammatory and acetylcholine protective effects.

Repeated column chromatography resulted in the isolation of two new glycosides, miliusides A-B (1 and 7), along with six known metabolites (2-6, and 8) from the leaves of Miliusa sinensis Finet and Gagnep. The structures of the purified phytochemicals were elucidated by interpreting their spectroscopic data (NMR, HRMS), as well as comparison with the previous literature. The biological evaluation of acetylcholinesterase (AChE) inhibitory effects and anti-inflammatory activity by measuring nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 mouse macrophage cells, were also conducted. Among them, compounds 5 and 7 exhibited significant AChE inhibitory activities (IC50 = 53.36 ± 4.20 and 88.50 ± 8.79 µM, respectively), compared with the positive control (Galanthamine, IC50 = 1.65 ± 0.15 µM). Only the MeOH extract showed suppression effects on NO production in LPS-induced RAW264.7 cells (IC50 = 38.18 ± 3.25 µg/mL) comparable to that of the positive control, l-NMMA (IC50 = 2.21 ± 0.56 µg/mL).