Simultaneous optimisation of extraction of xanthone and benzophenone α-glucosidase inhibitors from Cyclopia genistoides and identification of superior genotypes for propagation

Abstract

Extraction of xanthones and benzophenones from Cyclopia genistoides was optimised in terms of solvent composition (ethanol concentration) and extraction temperature, using a central composite design, response surface methodology and multi-response desirability profiling. Compounds of interest were the xanthones, mangiferin and isomangiferin, and the benzophenones, 3-β-d-glucopyranosyl-4-β-d-glucopyranosyloxyiriflophenone and 3-β-d-glucopyranosyliriflophenone, present in high levels in C. genistoides. Optimum extraction conditions (40% ethanol; 70°C; 10:1 solvent:solid ratio; 30min) applied to different batches of plant material (n=10), delivered mean extract, xanthone and benzophenone yields of 37.8, 4.12 and 1.99g/100g plant material, respectively, with a mean α-glucosidase inhibitory activity of 39.5% at 100μg/mL. Similar α-glucosidase inhibitory activity was demonstrated for mangiferin and isomangiferin, indicating that the position of the sugar moiety on the dibenzo-γ-pirone structure did not affect activity. Superior C. genistoides genotypes in terms of xanthone and benzophenone content were identified.