Antioxidant and Antimicrobial Activity of Oak (Quercus spp.) Acorn Collected in Lithuania

Acorns, also called as oak nuts, are fruits of oak tree (Quercus spp.). Acorn coffee is the most popular form of usage of acorns in Lithuania. However, studies show wider applications of acorns as functional food or food ingredient [1-3]. The antiproliferative and apoptosis-inducing activities [4], antioxidant and antibacterial activities [3] of acorn extracts are also studied and described. The studies reveal that all activities of plants strongly depend on their species, geographic origin and growing conditions. The method of sample preparation also has a high impact on the various activities of the plants. The aim of this study was to compare antioxidant and antimicrobial activities of acorn extracts prepared using different approach. Acorns were collected in three places in Lithuania. The grinded fresh acorns were extracted with methanol using different conditions, i.e. in room temperature, using exposure to ultrasound, applying ultrasound with heating, using only heating. Antimicrobial activity of prepared extracts was tested against some bacteria (Micrococcus luteus, Enterococcus faecalis, and Bacillus cereus) and fungi (Alternaria alternate and Penicillium funiculosum) using well diffusion assay. Not all extracts inhibited growth of all tested bacteria, the inhibition level was strain and extract preparation method depended. Similarly not all extracts showed antifungal activity. Spectrophotometric tests were used to evaluate the antioxidant activity and total flavonoid content in the extracts. Both antioxidant activity and flavonoid content varied between differently prepared extracts. Antioxidant and antibacterial activity in the tested samples also were depended on the acorn collection place, what might be related with oak tree genotype or phenotype. To our knowledge such study of acorns collected in Lithuania had not been performed beforeGamtos mokslų fakultetasInstrumentinės analizės APCVytauto Didžiojo universiteta