RESUMEN
Phytochemical investigation of the methanol extracts from the leaves and bark of Senna siamea resulted in the isolation of one new flavone C-glycoside: apigenin-8-C-[6''-(E)-feruloyl]-ß-D-glucopyranoside] (1), together with sixteen known compounds including quercetin-3-O-α-L-rhamnoside (2), vitexin (3), isovitexin (4), quercetin-3-O-ß-D-glucopyranoside (5), quercetin-3-O-ß-D-arabinopyranoside (6), quercetin (7), kaempferol (8), methyl inositol (9), sucrose (10), betulinic acid (11), vanillic acid (12), stigmastane-3ß,6α-diol (13), aurantiamide acetate (14), robinetinidol (15), catechin (16) and epicatechin (17). The structures of these compounds were established on the basis of their spectroscopic (1 D and 2 D NMR) and mass spectrometric (ESI-TOF-MS) data. The methanol extracts, fractions and some of the isolated compounds were screened for their antimicrobial properties against five microbial strains. The methanol extract and the ethyl acetate fraction from the bark showed very weak antifungal activity against C. glabrata with the same MIC value of 128 µg/mL. Compound 7 was weakly active against C. albicans with MIC of 32 µg/mL.
RESUMEN
This paper describes eight new triterpenoid saponins, including afzeliioside A (1), four acetylated afzeliiosides as pairs of inseparable regioisomers, called afzeliiosides B/C (2/3) and D/E (4/5), afzeliiosides F-H (6-8), and a known impatiprin C (9), which were isolated from the n-BuOH fraction of the liana of Microglossa afzelii. Their structures were established mainly by extensive spectroscopic analysis, including 1D and 2D NMR, HRFAB-MS, tandem ESI-MS/MS, and chemical methods, as well as a comparison of their spectral data with those of related compounds. All the isolates were screened for their cytotoxic activity against the CAL-27 oral squamous carcinoma cell line. Only compounds 4/5 (EC50 = 36.0 µg/mL (32.7 µM)) exhibited moderate cytotoxic activity. This work presents the first chemical and biological investigation of Microglossa afzelii and reports, for the first time, on the isolation of saponins in the genus Microglossa.