Densitometric TLC analysis for the control of tropane and steroidal alkaloids in Lycium barbarum

Thin layer chromatographic methods for quantitative determination of nightshade-specific tropane (l-hyoscyamine, scopolamine) and steroidal alkaloids (α-solanine, α-chaconine) in goji berries (L. barbarum L., Solanaceae) were developed. The analysis of tropane derivatives included separation on silica gel-coated HPTLC plates using mobile phase consisted of chloroform:methanol:acetone:25% ammonium hydroxide (75:15:10:1.6 v/v/v/v), derivatization with Dragendorff reagent and scanning densitometry at λ - 520nm in reflectance/absorption mode. Steroidal alkaloid analysis employed silica gel-coated TLC plates, mobile phase composed of chloroform:methanol:water:25% ammonium hydroxide (70:30:4:2 v/v/v/v), derivatization with Carr-Price reagent and video densitometry under white light in the reflectance mode. Both methods were validated with respect to linearity, precision, accuracy and sensitivity, enabling reliable detection of tropane derivatives and α-solanine at 1.20 and 7.84mgper100g fresh material, respectively. None of the analyzed compounds were detected in fruits, leaves, stems and roots of three L. barbarum varieties ('No. 1', 'New Big' and 'Amber Sweet Goji').