Abstract
Four new polyphenols, loddigesiinols G–J (compounds 1–4) and a known compound, crepidatuol B (5), were isolated from the stems of Dendrobium loddigesii that have long been used in Traditional Chinese Medicine and have recently been used to treat type 2 diabetes. Compounds 1–5 structures were elucidated based on spectroscopic analysis. The absolute configurations of compounds 1–4 were determined using theoretical calculations of electronic circular dichroism (ECD), and the absolute configuration of compound 5 was determined by a comparison of the experimental ECD spectra and the literature data. Compounds 1–5 are strong inhibitors of α-glucosidase, with IC50 values of 16.7, 10.9, 2.7, 3.2, and 18.9 μM, respectively. Their activities were significantly stronger than trans-resveratrol as a positive control (IC50 values of 27.9 μM).
Highlights
80 Dendrobium species (Orchidaceae), called “Shi Hu” in Chinese, are distributed across China; 50 of these species have long been used in Traditional Chinese Medicine [1,2]
Chemical studies of D. loddigesii have yielded bibenzyls, phenanthrenes, alkaloids, and lignans [7,8,9], but the chemical constituents of D. loddigesii that are responsible for lowering blood glucose levels have not been reported
The chemical study of the stems of D. loddigesii resulted in the isolation of four new polyphenols, and a known compound based on the previous research [10]
Summary
80 Dendrobium species (Orchidaceae), called “Shi Hu” in Chinese, are distributed across China; 50 of these species have long been used in Traditional Chinese Medicine [1,2]. D. loddigesii, which are the most important “Shi Hu” crude drug, have been used for the treatment of gastrosis, fever, and dizziness [3]. This herb has recently been used to treat type 2 diabetes. Animal and human studies have shown anti-diabetic effects of D. loddigesii stem extract (the traditional Chinese medicine apozem) [4,5,6]. We have initiated a program of phytochemical and biological studies of the stems of D. loddigesii; many known compounds were isolated, seven of which had been reported [10]. 27.9 μM) [11,12]
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