Termitomenins F and G, Two New Lignan Glucosides from Terminalia chebula var. tomentella (Kurz) C. B. Clarke

Abstract

The extensive chemical investigation on the branches and leaves of Terminalia chebula var. tomentella (Combretaceae) led to the isolation of two new lignan glucosides with a furofuran skeleton, termitomenins F (1) and G (2). In addition, 19 known compounds including five lignan glucosides (3–7), six hydrolyzable tannins (8–13) and eight simple phenolics (14–21) were also identified. Their structures were determined by comprehensive spectroscopic analyses. It is noted that 8 and 9 were C-glycosidic hydrolyzable tannins with one hexahydroxydiphenoyl and one gallagyl group linked to an open-chain glucosyl C-1/O-2/O-3 and O-4/O-6, respectively, which were rarely found in plants. Nine known compounds, 6–9, 13, and 18–21, were procured from the titled plant for the first time, while 3–5, 10–12 and 14–17 were also found in the fruits. Notably, the known hydrolyzable tannins 8–13 exhibited stronger α-glucosidase inhibitory activities with IC₅₀ values ranging from 0.10 to 3.12 μM, than the positive control, quercetin (IC₅₀ = 9.38 ± 0.33 μM).

Graphic abstract