A new method for the production of enriched polyphenolic extracts from propolis using adsorption resins

Abstract

In previous works we have presented several applications for the production of enriched polyphenolic extracts from raw materials (olive mill waste water [1], winery byproducts, sesame [2]) using adsorption resins. Herein we describe the development of a new method for the production of enriched extracts from propolis. More specifically, two raw propolis samples (from geographically distinct regions of Greece: North Aegen and Crete) were first submitted to hydrodistillation in order to obtain the contained essential oil (0.14% and 0.12%) and the aqueous residue was filtered to remove the insoluble material (mainly non volatile terpenes and hydrocarbons: 61.2% and 60.5%). The filtrate was allowed to cool and the solidified wax (34.2% and 34.0%) was removed. The obtained clear solution was passed through a column containing adsorption resin XAD-4. The adsorbed polyphenols were desorbed using methanol and the obtained extract (1.8% and 1.5%) was analyzed by HPLC-UV. The contained phenolic acids (e.g. caffeic, p-coumaric, ferulic) and flavonoids (e.g. pinobanksin) showed 50–100 fold increased concentration in comparison with the raw propolis. In parallel, the essential oil obtained during the first step was analysed by GCMS showing α-pinene as the major component (40.3%, 46.6%) followed by at least 25 common constituents. Chiral GCMS analysis showed significant differences in the (+)/(–) α-pinene ratio between the two samples suggesting that this factor could be very useful in the discrimination of propolis samples