Propolis extracts obtained by low pressure methods and supercritical fluid extraction

Propolis is a natural product used for centuries by human kind, due to several evidenced biological activities: antioxidant, antimicrobial, anti-inflammatory, antitumor and anti-HIV. Extracts from propolis, used in food, pharmaceutical and cosmetic industries, present quality and composition related to the extraction method applied. Natural compounds with biological activity can be obtained by conventional techniques, such as Soxhlet and Maceration, or by alternative methods such as supercritical fluid extraction (SFE). Thus, the aim of this work was to compare propolis extraction yields obtained by different procedures, for instance, SFE in one stage, with CO₂ and CO₂ plus co-solvent, and SFE in two stages, as well as Soxhlet and Maceration as low pressure extraction methods using ethanol, ethyl acetate, chloroform, n-hexane, water and mixtures of water/ethanol. The operational conditions for SFE in one stage with pure CO₂ were: 30, 40 and 50 °C and from 100 to 250 bar. The SFE with co-solvent was performed at 150 bar and 40 °C and ethanol concentrations of 2, 5 and 7% (w/w). The highest yield was obtained by chloroform Soxhlet extraction (73 ± 2%, w/w) whereas for SFE the maximum yield was 24.8 ± 0.9%, using 5% ethanol as co-solvent. For SFE in two stages, 100 and 150 bar were used in the first stage while 250 and 300 bar were applied in the second stage, at 40 °C. The yields were 8.4 ± 0.7 (150 bar) and 5.1 ± 0.7 (250 bar), for stages 1 and 2, respectively. The chemical composition of the propolis material was determined by HPLC analysis. The experimental data were correlated using four models based on differential mass balance equations: (1) the Sovová’s model; (2) the logistic model (3) the diffusion model and (4) the simple single plate model (SSP). The logistic model provided the best adjustment for propolis SFE curves.