Dynamics of squalene content in different tissues of Ashwagandha (Withania somnifera L. Dunal) during its growth phases

• The changes of dynamics of squalene content at four different growth phases were analyzed via HPLC in four tissues of Withania somnifera.
• Maximal increase of squalene content was observed in GP III, the end of the vegetative phase.
• Our results suggested that leaves were the richest in squalene content among analyzed tissues of Withania followed by stems, roots and berries.
• The regulatory role of squalene content in the biosynthesis of withanolides was inferred.

The changes of dynamics of squalene content in different tissues (leaves, stems, roots and berries) of Ashwagandha (Withania somnifera L. Dunal) was analyzed at different growth phases via high-performance liquid chromatography (HPLC). The concentration of squalene was evaluated in growth phase I (GP I, early vegetative), phase II (vegetative with the initiation of flowers), phase III (full blossom with the initiation of berries) and phase IV (matured with profuse berries). In all growth phases (GP), the highest concentration of squalene ranged in leaves from 8.33 to 9.96 μg/g. Maximal increase of squalene was observed in GP III (4.38, 5.61 & 3.41 times) than GP I and GP IV (76.38, 3.08 & 1.34 times) in leaves, stems and roots, respectively. The trend of squalene content in Withania followed: leaves > stems > roots > berries. In leaves, an average of squalene was 9.66 times higher than berries at growth phase III. The highest turnover rate of squalene epoxidase (EC 1.14.99.7) enzyme based on HPLC separation coupled with UV/visible detector was up to 10 min and then declined with depletion of squalene over a period of time. The regulatory role of squalene content in the biosynthesis of withanolides in the case of leaves has also been inferred. From the standpoint of the content of squalene in different tissues, the leaves are the richest part and the end of the vegetative period (GP III) is the optimum growth phase for squalene extraction in W. somnifera.