Isolation of the major compounds and determination of biological activities in the underground parts of trachystemon orientalis d.Don

Abstract

Objectives: Trachystemon orientalis D.Don, an edible plant, is widely used in folk medicine. This study aimed to investigate the antioxidant and lipase inhibitory activities of the extracts and isolated compounds from the underground parts of T. orientalis (TOU). Materials and Methods: Isolation studies were carried out on the subextracts (the chloroform, ethyl acetate and remaining aqueous) prepared from the methanol extract of TOU using various chromatographic methods, and the structures of the purified compounds were determined by 1D-NMR, 2D-NMR, and mass spectroscopy techniques. To determine antioxidant activity, ferric-reducing antioxidant power (FRAP) and Cu(II) ion-reducing antioxidant capacity (CUPRAC) assays were performed. Lipase inhibitory activity was determined using an in vitro spectrophotometric method. Results: In the isolation studies, rosmarinic acid (1) was isolated from the ethyl acetate subextract and danshensu (2), globoidnan B (3), and rabdosiin (4) were isolated from the remaining aqueous subextract. These compounds were isolated from TOU for the first time. The ethyl acetate subextract had higher activity than the other extracts in the FRAP and CUPRAC assays (794.818 ± 8.999, 583.06 ± 5.882 µM Trolox equivalents (TE)/g), respectively] and rosmarinic acid exhibited the highest activity [1260.273 ± 4.499, 608.250 ± 1.195 µM TE/g, respectively). Lipase enzyme inhibitory studies showed that the remaining aqueous and ethyl acetate subextracts had significant inhibitory activity [half maximal inhibitory concentration (IC)50 = 38.131 ± 0.720, 38.841 ± 1.359 µg/mL respectively). All isolated compounds inhibited lipase, and rosmarinic acid was the most effective (IC50 = 49.421 ± 1.448 µg/mL). Conclusion: According to the results of this study, T. orientalis and its isolated compounds may be a promising natural therapeutic agent for the treatment of obesity via its high antioxidant capacity and lipase inhibitory activity.