New sesquiterpene and flavone arabinofuranoside derivative from the leaves of Fissistigma bicolor.

A new muurolane-type sesquiterpene, a new flavone arabinofuranoside derivative, and other five known flavone arabinofuranoside derivatives were isolated from the leaves of Fissistigma bicolor (Annonaceae family). Their chemical structures were determined to be (1S,6R,7S)-muurola-4,10(14)-diene-15-ol (1), quercetin 3-O-ß-D-apiofuranosyl-(1→2)-α-L-arabinofuranoside (2), quercetin 3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinofuranoside (3), quercetin 3-O-α-L-arabinofuranoside (4), kaempferol 3-O-ß-D-apiofuranosyl-(1→2)-α-L-arabinofuranoside (5), kaempferol 3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinofuranoside (6), and kaempferol 3-O-α-L-arabinofuranoside (7) by analyses of HR-ESI-MS and NMR spectral data. Compounds 4 and 7 containing monosaccharide, arabinofuranoside, potentially inhibited NO productions in LPS activated RAW264.7 cells (IC50 13.4 ± 0.5 and 12.6 ± 0.4 µM) in compared to disaccharide derivatives (IC50 ranging from 58.9 ± 3.3 to 65.6 ± 3.8 µM).

Garcicowanones C-E, three new hydrated-geranylated xanthones from the roots of Garcinia cowa Roxb. ex Choisy, and their α-glucosidase inhibition activities.

Three new xanthones, garcicowanones C-E (1 - 3), and six known xanthones (4 - 9) were isolated from the roots of Garcinia cowa Roxb. ex Choisy. Their chemical structures were determined using spectroscopic technics, including HR-ESI-MS and 2 D NMR. All isolated compounds were evaluated for in vitro α-glucosidase inhibition. Cowanol (6) and norcowanin (8) had the most potent α-glucosidase inhibitory activity, with respective IC50 values of 33.5 ± 0.8 and 17.2 ± 0.3 µM, compared with the positive control, acarbose (IC50 257.3 ± 4.8 µM).

Wedtrilosides A and B, two new diterpenoid glycosides from the leaves of Wedelia trilobata (L.) Hitchc. with α-amylase and α-glucosidase inhibitory activities.

In the ongoing research to find new diabetes constituents from the genus Wedelia, the chemical constituent of Wedelia trilobata leaves, a Vietnamese medicinal plant species used to treat type 2 diabetes mellitus, was selected for detailed investigation. From a methanolic extract, two new ent-kaurane diterpenoids, wedtrilosides A and B (1 and 2), along with five known metabolites (3-7), were isolated from W. trilobata. The chemical structures of (1-7) were assigned via spectroscopic techniques (IR, 1D, 2D NMR and HR-QTOF-MS data) and chemical methods. The isolates were evaluated for α-amylase and α-glucosidase inhibitory activities compared to the clinical drug acarbose. Among them, compounds 4, 6, and 7 showed the most potent against α-glucosidase enzyme with IC50 values of 27.54 ±â€¯1.12, 173.78 ±â€¯2.37, and 190.40 ±â€¯2.01 µg/mL. While moderate inhibitory effect against α-amylase was observed with compounds 6 and 7 (with IC50 = 181.97 ±â€¯2.62 and 52.08 ±â€¯0.56 µg/mL, respectively). The results suggested that the antidiabetic properties from the leaves of W. trilobata are not simply a result of each isolated compound, but are due to other factors such as the accessibility of polyphenolic groups to α-amylase and α-glucosidase activities.