Isolation of the major compounds and determination of biological activities of the underground parts of Trachystemon orientalis

INTRODUCTION: Trachystemon orientalis (L.) G. Don, an edible plant is widely used in folk medicine. This study aimed to investigate antioxidant and lipase inhibitory activities of the extracts and isolated compounds of the underground parts of T. orientalis (TOU).
METHODS: The 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 MS spectral methods. To determine the antioxidant activity, ferric reducing antioxidant power (FRAP) and Cu(II) ion reducing antioxidant capacity (CUPRAC) assays were applied. Lipase inhibitory activity was determined by in vitro spectrophotometric method.
RESULTS: By the isolation studies, rosmarinic acid (1) was isolated from the ethyl acetate subextract, and danshensu (2), globoidnan B (3), and rabdosiin (4) from the remaining aqueous subextract. These compounds were isolated from TOU for the first time. The ethyl acetate subextract had higher activity compared to 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 the ethyl acetate subextracts had significant inhibitory activity (IC50 = 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).
DISCUSSION AND CONCLUSION: According to the results of this study, T. orientalis and its isolated compounds may be a promising natural therapeutic for the treatment of obesity via its high antioxidant capacity and lipase inhibitory activity.