Strategy of experimental design for intensification of solvent extraction of natural antioxidant flavonoids and phenols from buckthorn textured leaves

Prior to solvent extraction of plant-based active molecules, adequate texturing by Detente Instantanee Controlee (DIC; French for "Instant controlled pressure drop") results in overcoming the slow diffusion of the solvent/solute through the solid matrix. This work aimed at determining the impact of DIC pretreatments on buckthorn (Rhamnus alaternus L.) morphology. DIC-operating parameters were selected as the saturated steam pressure, the thermal treatment time, and the number of cycles. A three-parameter five-level response surface method was used to optimize DIC processing parameters. Response factors were the overall and individual yields of flavonol aglycone extraction, and antioxidant activity of both expanded dried material (swell dried leaves) and extracts. The yield of flavonol aglycones was 18.23 mg Kaemp eq/g dry basis (mg Kaemp eq/g db) in 3 min for DIC-treated buckthorn, against 12.24 mg Kaemp eq/g db in 150 min for untreated natural buckthorn raw material. Furthermore, the antioxidant activity of DIC-treated material was exceptionally higher and the effectiveness of reducing power of DPPH radical was 68 times more than the untreated plant material.