Antioxidant and Antibacterial Properties of Castanea sativa Mill. Catkins Extracts

Recently the role of phenolic compounds as protective dietary constituents has become an increasingly important area of human nutrition research. So far the application of extract of sweet chesnut in diet and therapy was poorly studied. Samples of catkins of sweet chestnut and grafted Italian marrone cultivar have been collected in Bosnia and Herzegovina. The samples were milled for further analysis. After the addition of 250 ml of 50% ethanol to 50 g of each sample, extraction of the ethanol dissolving compounds was performed by ultrasound (30 min). The samples were filtrated and dried by evaporation under vacuum at 313 K. The extracts were kept at 193 K. With intention to simulate metabolism of tannins in human intestine and to simplify the analysis, chestnut extracts were submitted to methanolysis. The identification of the constituents of the extracts after methanolysis was performed by LC/MS and HPLC/DAD. The antioxidative properties of extracts was invetigated by application of electron paramagnetic resonance (EPR) technique. In the other hand, the disc-diffusion method was used as a test for antimicrobial activity. The identified compounds in examinated extracts could be classified as ellagic acid or its derivatives, gallic acid derivates, flavonoids (quercetin, kaempferol, isorhamnetin) and coumaric acid methyl ester. The highest content of gallic acid derivates was obtained in extract of grafted Italian marrone cultivar 136.8 mg/g, experessed as gallic acid per g of dry extract. Condensed and hydrolysable tannins are potentially more potent antioxidants than simple monomeric phenolics. The most prominent antioxidant activity against superoxide radical was detected for the extract of catkins of grafted Italian marrone (RI=85%). Total level of derivatives of ellagitannins showed statistically significant positive correlation with antioxidative activity of extracts against superoxide. The test extracts demonstrated significant antimicrobial activity, especially against both Gram-negative (Salmonella typhimurium) and Gram-positive (Micrococcus pyogenes var. albus and Staphylococcus aureus) bacteria. The growing interest in the substitution of synthetic food antioxidants by natural ones has fostered research on vegetable sources and the screening of raw materials for identifying new antioxidants. We found that Castanea sativa Mill. catkins extracts could be one with promising characteristics. Also, analysing extracts possesses great antimicrobial activity.