Enhancement of diosgenin extraction from Fenugreek (Trigonella foenum-graecum) with a new ionic liquid-based assisted method

Diosgenin is a steroidal sapogenin which is used extensively by both pharmaceutical and nutraceutical industries as a raw precursor for the production of steroidal drugs and hormones such as testosterone, glucocorticoids and progesterone [1]. One of the main sources of diosgenin is Fenugreek (Trigonella foenum-graecum L.) which is an annual crop and dicotyledonous plant belonging to the subfamily Papilionaceae, family Fabaceae. Fenugreek is most widely known as an aromatic and spice crop with a number of medicinal properties all over the world [2]. Diosgenin is the aglycone form of saponin dioscin, which commonly extracted by hydrolysis with inorganic acid, such as sulfuric and hydrochloric acid [3]. In addition, ionic liquids (ILs) are mentioned as the green solvents and have negligible vapor pressure, good thermal stability and considerable extraction capacity [4]. Although ILs cost more than the other usual solvents but they can be recycle and reuse for several times. These advantages are highly attractive to the present academic and industrial circles related to the natural functional resources [5]. In this study, 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM] HSO₄) as a catalytic amount has been used to extract the diosgenin from fenugreek leaves [5]. The efficiency of extraction has been monitored with high performance liquid chromatography (HPLC). The concentration of diosgenin in the IL assisted method under reflux condition has been compared with the conventional heat-reflux extraction and regular ultrasonic extraction and IL assisted ultrasonic extraction method. The concentration of the [BMIM] HSO₄ and time of reflux for diosgenin extraction along with the mass of the plant material have been optimized in this procedure. The optimized approach gained the highest extraction efficiency (from 4.9 to 11.85 mg diosgenin/g dw plant) within the shorter extraction time (from 120 min to 60 min). Considering the obtained result, the IL is a promising alternative for conventional inorganic acid catalysts during the diosgenin extraction.

Acknowledgements: The author wish to thank Tarbiat Modares University Research and Technology Council for the financial support and Institute of chemistry and chemical engineering of Iran for their technical supports.

Keywords: Fenugreek, diosgenin, ionic liquid, [BMIM] HSO₄, HPLC, steroidal saponins.

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