Bioactive Constituents Obtained from the Seeds of Lepidium apetalum Willd

Three new compounds, apetalumosides C1 (1), D (2), and 1-thio-β-d-glucopyranosyl(1→1)-1-thio-α-d-glucopyranoside (3), together with twenty-two known ones (4–25) were obtained from the seeds of Lepidium apetalum Willd. Among the known isolates, 5–8, 10–13, 16–20, and 25 were obtained from the genus for the first time; 4, 14, 15, and 21–24 were isolated from the species for the first time. Meanwhile, the NMR data of 16 was first reported here. Their structures were determined by means of chemical and spectroscopic methods. On the other hand, their inhibitory effects on sodium oleate-induced triglyceride (TG) overloading in HepG2 cells were evaluated. As a result, two new compounds (1 and 2), together with known isolates 7–11, 13, 14, 16–18, 20, 21, and 25 possessed significant inhibitory effects in the cells.


Results and Discussion
The 50% EtOH extract of L. apetalum seeds was treated with the same experimental process as reported in reference [1,2] to obtain 95% EtOH eluate, which was separated by silica gel, octadecylsilica (ODS), Sephadex LH-20 CC, and finally preparative HPLC to yield compounds 1-25. Their structures are shown in Figures 1 and 2. Molecules 2017, 22, 540 2 of 10 one lignan (20), together with two new compounds (1 and 2), as well as two other isolates (21 and 25) exhibited significant triglyceride (TG)-lowering effects in HepG2 cells.

Results and Discussion
The 50% EtOH extract of L. apetalum seeds was treated with the same experimental process as reported in reference [1,2] to obtain 95% EtOH eluate, which was separated by silica gel, octadecylsilica (ODS), Sephadex LH-20 CC, and finally preparative HPLC to yield compounds 1-25. Their structures are shown in Figures 1 and 2.   one lignan (20), together with two new compounds (1 and 2), as well as two other isolates (21 and 25) exhibited significant triglyceride (TG)-lowering effects in HepG2 cells.
As for structure-activity relationships, quercetin glycosides (7 and 8) and isorhamnetin glycosides (9)(10)(11) in the current study showed significant TG-lowering effects, while kaempferol glycosides (4-6) exhibited no obvious activity, which indicated that the 3′-position substitution of hydroxyl or methoxy might play critical roles on the TG-lowering activity of flavone glycosides. For apetalumoside C1 (1), a previous study has reported that the substitution of 7-position by O-glycosides would reduce According to the results shown in Figure 5 Tables 4 and 5).
As for structure-activity relationships, quercetin glycosides (7 and 8) and isorhamnetin glycosides (9)(10)(11) in the current study showed significant TG-lowering effects, while kaempferol glycosides (4)(5)(6) exhibited no obvious activity, which indicated that the 3 -position substitution of hydroxyl or methoxy might play critical roles on the TG-lowering activity of flavone glycosides. For apetalumoside C1 (1), a previous study has reported that the substitution of 7-position by O-glycosides would reduce the inhibitory activities of flavonoid glycosides [2], while in the current study, 1 still exhibited a strong effect with the glycosylation of 7-hydroxyl; this is speculated to be due to the presence of the sinapoyl group in the structure. Meanwhile, five of the six sinapic acid homologues in our study, including 13, 14, and 16-18, showed significant TG-lowering activities. By comparing the TG clearance rate of 17 (12.39% ± 0.95%) with that of 18 (5.49% ± 3.17%), at the concentration of 30 µmol/L, as well as the difference of their structures, we speculated that the one additional glycosyl might be the reason for the reduced activity. However, it is noteworthy that sinapoylglucose (15) showed lower activity than that of sinapoyl-9-sucrosecoside (16), which made it complicated to illustrate the influence of the substituted position and amount of glycosyl on the activity of sinapic acid groups.
Molecules 2017, 22, 540 6 of 10 the inhibitory activities of flavonoid glycosides [2], while in the current study, 1 still exhibited a strong effect with the glycosylation of 7-hydroxyl; this is speculated to be due to the presence of the sinapoyl group in the structure. Meanwhile, five of the six sinapic acid homologues in our study, including 13, 14, and 16-18, showed significant TG-lowering activities. By comparing the TG clearance rate of 17 (12.39 ± 0.95%) with that of 18 (5.49 ± 3.17%), at the concentration of 30 µmol/L, as well as the difference of their structures, we speculated that the one additional glycosyl might be the reason for the reduced activity. However, it is noteworthy that sinapoylglucose (15) showed lower activity than that of sinapoyl-9-sucrosecoside (16), which made it complicated to illustrate the influence of the substituted position and amount of glycosyl on the activity of sinapic acid groups.

Plant Material
The seeds of L. apetalum were collected from Anguo city, China, and identified by Dr. Li Tianxiang

Extraction and Isolation
The seeds of L. apetalum (10 kg) were treated with the same experimental process as reported in reference [1,2], as a result, the 95% EtOH (Fraction 1) and H 2 O (Fraction 2) eluates were obtained.