Çeşitli ekstraksiyon ve fermentasyon işlemlerinin bal, propolis ve polen örneklerinin antioksidan kapasitesi üzerine etkileri

Various honeybee products attract great attention of food, pharmaceutical and cosmetics industries due to their nutritive properties and healthful effects such as antioxidant, antimicrobial, anticancer etc. activities. The aim of current study is to determine the effects of different extraction processes utilizing different solvents and ambient temperatures onto the antioxidant capacity of honey, propolis and bee pollen samples, and to evaluate whether fermentation process, which is known to enhance beneficial effects of some food products by increasing and/or transforming the active constituents both in quality and quantity, changes the antioxidant capacity of the most active sample. Oak honey sample, two (autumn and spring) propolis samples and pollen sample were obtained from a local beekeeper in Kırklareli province (Turkey). The samples were extracted individually with different solvents [100% (v/v) methanol, 70% (v/v) ethanol and distilled water] at three different temperature conditions (room temperature for 24 hour, 45oC for 24 hour and 45oC for 24 hour + boiling for 2 hour). DPPH, Folin-Ciocalteu and aluminum chloride methods were performed to assess the radical scavenging activity, total phenolic content (TPC) and total flavonoid content (TFC) of the samples, respectively. Since the highest radical scavenging activity was detected in the extract of autumn propolis obtained by the extraction method utilizing ethanol as a solvent and 45oC for 24 hour + boiling for 2 hour as temperature condition, this sample was fermented using Lactobacillus brevis, and antioxidant capacity of fermented propolis was measured. The results obtained for the same type of product as well as for different groups of products were compared and discussed. Among honey samples, the highest TPC was found in the aqueous extract prepared by boiling, as 0.90 ± 0.09 mg gallic acid equivalent (GAE)/g dry weight of extract (DWE) while the highest TFC was detected in methanol extract prepared in room temperature as 0.055 ± 0.002 mg quercetin equivalent (QUE)/g of DWE. This extract also showed the highest radical scavenging activity with the lowest IC50 (157.0 ± 9.8 mg/mL). Among propolis samples, the best TPC, TFC and IC50 values were found in the extract obtained by extraction of autumn propolis with ethanol at 45 oC for 24 hour + boiling for 2 hour, as 340.4 ± 34.5 mg GAE/g DWE, 103.5 ± 5.2 mg QUE/g DWE and 0.011 ± 0.001 mg/mL, respectively. In fact, this extract was also the most active one among all samples of three honeybee products, and hence the fermented one in this study. Among pollen samples, the best TPC, TFC and IC50 values were found in ethanol extract prepared at room temperature, as 22.8 ± 1.2 mg GAE/g DWE, 4.68 ± 0.30 mg QUE/g DWE and 5.8 ± 0.8 mg/mL, respectively. Fermentation of propolis was acheived in 6 days, and TPC, TFC and antioxidant capacity tests were carried out in various samples of second, fourth and sixth days of fermentation, before and after centrifugation. The best values for TPC, TFC and IC50 were determined in unfermented (no bacteria were added in assay conditions) pasteurized propolis sample, quite close each other at the second and sixth days, as a mean 268.15 mg GAE/g DWE, 23.9 mg QUE/g DWE, 0.047 mg/mL, respectively. The highest TPC, TFC and the lowest IC50 values in fermented propolis after centrifugation were found for the second day of fermentation as 46.7 ± 1.1 mg GAE/g DWE, 9.65 ± 1.5 mg QUE/g DWE and 0.220 ± 0.005 mg/mL, respectively. The data related to fermentation indicated that antioxidant capacity and principal active phenolic substances of propolis significantly decreased during the fermentation process day by day. Overall findings reveal that solvent type and temperature in extraction as well as fermentation may affect the antoxidant capacity and the chemical composition of honeybee products. Besides, particularly autumn propolis seems to be one of the the best bee products as a natural antioxidant, or as a source of new antioxidants, since its decoction in ethanol exhibits an effective radical scavenging activity because of its high phenolic and flavonoid content. This study is expected to be a guide for further studies targeting to exhibit or produce new honeybee products and related substances beneficial for human health and welfare, and to contribute to the attempts for increasing the industrial value of these products.