Saponins from the Leaves of Panax vietnamensis Ha et Grushv. (Vietnamese ginseng) and Their Inhibitory Activities on α-Glucosidase

Vietnam boasts a rich and diverse flora, with many endemic species. Among them, Ngoc Linh ginseng (Vietnamese ginseng; scientific name: Panax vietnamensis Ha et Grushv.), a high-value endemic ginseng species, has been recognized as a national treasure. While numerous studies have been conducted on its rhizomes and roots, research on its leaves remains limited. In this study, six compounds (1–6) were isolated from the methanol extract of the leaves of P. vietnamensis. Their structures were elucidated using ESI-MS, 1D and 2D NMR spectroscopic methods, and comparisons with known literature data. The identified compounds are: 12β,20(R),25-β trihydroxydammara-3-O-β-D-glucopyranoside (1); 12β,20(R),25-trihydroxydammara-3-O-β-D-glucopyranosyl- (1→2)-β-D-glucopyranoside (2); notoginsenoside SFt1 (3); ginsenoside Rh2 (4); ginsenoside Rg3 (5) and notoginsenoside L1 (6). Except for compound 3, which was isolated from the leaves for the first time, the other five compounds are reported from this species for the first time. The α-glucosidase inhibition assay of the pure isolated compounds revealed that compounds 1, 4, and 6 exhibited significant activities, with IC₅₀ values of 133.5, 105.5, and 14.9, respectively. For comparison, the positive control, acarbose, had an IC₅₀ value of 138.2 µM.