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

- Mangiferin and isomangiferin were equally effective as α-glucosidase inhibitors.
- Xanthone and benzophenone extraction was simultaneously optimised.
- Optimised extraction was obtained using 40% ethanol at 70 °C.
- Genotypes were differentiated mainly based on iriflophenone diglucoside content.
- A high leaf-to-stem ratio could be used to select superior genotypes.

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; 30 min) applied to different batches of plant material (n = 10), delivered mean extract, xanthone and benzophenone yields of 37.8, 4.12 and 1.99 g/100 g plant material, respectively, with a mean α-glucosidase inhibitory activity of 39.5% at 100 μg/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.