Structurally diverse biflavonoids from the fruits of Citrus medica L. var. sarcodactylis Swingle and their hypolipidemic and immunosuppressive activities

The fruit of Citrus medica L. var. sarcodactylis Swingle is not only used as a traditional medicinal plant, but also served as a delicious food. Six new (3'→7″)-biflavonoids (1-6), and twelve known biflavonoid derivatives (7-18) were isolated and characterized from the fruits of C. medica L. var. sarcodactylis Swingle for the first time. Their structures were determined by extensive and comprehensive analyzing NMR, HR-ESI-MS, UV, and IR spectral data coupled with the data described in the literature. Compounds (1-18) were evaluated for their hypolipidemic activities with Orlistat as the positive control, and assayed for their immunosuppressive activities with Dexamethasone as the positive control, respectively. Among them, compounds (1-3) exhibited moderate inhibition of pancreatic lipase activity by inhibiting 68.56 ± 1.40%, 56.18 ± 1.57%, 53.51 ± 1.59% of pancreatic lipase activities at the concentration of 100 μM, respectively. Compounds (4-6) and 8 showed potent immunosuppressive activities with the IC50 values from 16.83 ± 1.32 to 50.90 ± 1.79 μM. The plausible biogenetic pathway and preliminary structure activity relationship of the selected compounds were scientifically summarized and discussed in this study.