Steroidal Saponins from the Seeds of Chinese Trigonella foenum-graecum L

Trigonella foenum-graecum L. (fenugreek, leguminosae), which is an annual herb, has been widely cultivated in China, and the seeds of this plant have long been known as a traditional medicine used for tonic and stomachic purpose [1]. Previous pharmacological research on fenugreek seeds revealed their potential bioactivities of anti-diabetes and anti-lipemia. The steroidal saponins, which are the principle constituents of fenugreek seeds, could significantly induce hypoglycaemia and hypocholesterolemia [2]. According to our studies, fenugreek seeds abound in furostanol saponins, but few spirostanol saponins exsit in these seeds. Due to our structure-activity relationship research, the spirostanol saponins are more active than the corresponding furostanol saponins on antifungal activity and platelet aggregation [3, 4]. Thus, we converted the furostanol saponins of fenugreek seeds to the spirostanol saponins by enzymatic hydrolysis with β-gucosidase. The obtained total spirostanol saponins presented significant antifungal property.

We carried out the phytochemical investigation on the native steroidal saponins and their biotransform products from Chinese fenugreek seeds by column chromatography on macroporous resin SP825, silica-gel, and ODS silica-gel, and semi-preparative RP-HPLC, leading to the isolation of 46 compounds (23 furostanol saponins, 15 spirostanol saponins and 8 flavonoid-C-glycosides). Their structures were evaluated by HR ESI-MS, 1D-NMR (¹H-NMR, ¹³C-NMR) and 2D-NMR (¹H-¹H COSY, HSQC, and HMBC) spectroscopic techniques and chemical evidences. 17 steroidal saponins (8 furostanol saponins, 9 spirostanol saponins) are new compounds and 2 furostanol saponins were isolated from the seeds for the first time.

References: [1] Pharmacopoeia of People's Republic of China (2010) [2] Petit PR, Sauvaire YD, et al. (1996) Steroids, 60: 674–680. [3] Fu YL, Yu ZY et al. (2008)J Thromb Haemost, 6; 524–33. [4] Guo L, Su J, et al. (2008) Hum Reprod, 23(4): 964–71.