engleski

Honey: Effect of extraction type on phenolic content and antioxidant capacity results

Methodological approach for determination of phenolic compounds and antioxidant capacity of honey differs between research papers. Extraction process is an important step in the evaluation of total phenolics and antioxidant capacity, but most of the available data on phenolic composition of honey originate from spectrophotometric methods performed without extraction, directly on fresh honey samples, often with different solvents. In this study we screened for the possible differences in total phenolics and antioxidant capacity results depending on the extraction type to which the honey was subjected. Experiments were performed using honey of Castanea sativa, Tillia spp. and Robinia pseudoacacia species, in triplicates for each honey sample - (a) fresh honey dissolved in water, (b) fresh honey dissolved in ethanol and (c) ethanol extract prepared using column chromatography. In most cases, the results acquired with ethanol extract obtained by column chromatography had significantly higher readings (for example C. sativa: ABTS (42.1±2.1%), DPPH (48.6±0.7%), FRAP (91.9±0.4, total phenolics (160.1±12.9 mg galic acid equivalents/100 g of honey)) then the results acquired with both dilutions of fresh honey samples (C. sativa: dissolved in water - ABTS (24.2±0.4%), DPPH (24.6±1.5%), FRAP (81.3±0.2%), total phenolics (67.1±5.0 mg galic acid equivalents/100 g of honey) ; C. sativa dissolved in ethanol - ABTS (16.2±4.8%), DPPH (3.0±0.2%), FRAP (78.5±0.7%), total phenolics (44.1±9.2 mg galic acid equivalents/100 g of honey). Among the fresh honey samples, no strict tendency could be observed, in some cases water was better solvent, but in another ethanol was better (for example total phenolics in R. pseudoacacia were 14.9±4.2% for water dissolved honey, and 49.7±17.6% for ethanol dissolved honey, while FRAP was 44.7±0.1% for water dissolved honey, and 30.2±1.8% for ethanol dissolved honey). Furthermore, total phenolic content and antioxidant capacity results do not completely match between fresh honey samples and those extracted using column chromatography. These results imply that omission of extraction step using column chromatography reduces the sensitivity and specificity of spectrophotometric methods for assessment of total phenolics and antioxidant capacity of honey.

antioxidants ; column chromatography ; methodology ; polyphenols ; spectrophotometry

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