Purification of polyphenolic compounds from crude olive leaf extract

Abstract

Study was carried out to investigate the adsorption characteristics of olive leaf extract on the macroporous adsorption resins and the efficiency of the adsorption column for the separation and purification of oleuropein and rutin from the crude plant extract. Both static and dynamic experiments were performed. In static studies, the performances of three macroporous Amberlite resins namely XAD4, XAD 16 and XAD7HP for the adsorption of polyphenols were evaluated. XAD7HP was chosen as an adsorbent for further adsorption study. XAD7HP was selected for the studies of isotherms, kinetics of adsorption. In conventional alcohol extraction, crude feedstock is mixed with solvent which is alcohol for most cases, and then extract is distilled to remove ethanol. This process ends with a certain amount of residual ethanol because of complication in separation process for ethanol and water makes an azeotropic binary system. The results showed that adsorption capacity of an alcoholic solution with 10 % ethanol content is better than aqueous solution which contained no ethanol. In dynamic studies, the adsorption and desorption experiments were carried out on a glass column packed with XAD7HP resin. The flow velocity 122 cm/h operated as a fixed bed while operation was in an expanded bed mode at 367 cm/h and 611 cm/h, respectively. The effectiveness of the packed bed adsorption and the fluidized bed adsorption were compared. The results show the breakthrough occurred earlier when the feed flow velocity increased. In the elution step, elution program with 2,000 ml for 0 %, 4,000 ml for 40 % and 3,000 ml for 90 % aqueous ethanol was used to achieve an efficient separation. Total phenol content and antioxidant capacity of olive leaf crude extract and effluent fractions were analyzed in order to find the difference between before and after separation. Consequently, fluidized bed adsorption is a promising alternative for the packed bed adsorption in order to isolate oleuropein and rutin from the olive leaf extract.