Terpenoids with α-glucosidase inhibitory activity from Rhododendron minutiflorum Hu

• DOI: 10.1016/j.phytochem.2021.113083
• Publication Date: 2022-01-06T18:56:28Z
• Authors: Xian-Zhe Fan; Yang-Li Zhu; Rong-Wen Yuan; Li Deng; Cheng Hou; Wei Li; Ting Liu; Xiang-Qian Kong; Li-Jun Zhang; Hai-Bing Liao
• Keywords: Acarbose; IC50; Terpene

Five undescribed triterpenoids, two unusual omphalane-type sesquiterpenoids together with twenty-five known compounds were isolated from the leaves and stems of Rhododendron minutiflorum Hu. The absolute configurations of 1-3 and 6 were established by single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD). Compounds 6-7 feature the rare omphalane-type sesquiterpene skeleton and are verified by single-crystal X-ray diffraction analysis for the first time. In the biological activity assay, most of the triterpenoids have different degrees of inhibitory effects on α-glucosidase, with IC50 values ranging from 6.97 to 229.3 μM (the positive control drug acarbose has an IC50 value of 3.07 × 10-3 μM). Structure and activity relationship (SAR) study reveals that the oxidation degrees of C-3, C-8, or C-11 to C-13 of the ursane-type triterpenoid influence the inhibitory activity dramatically.