The impact of spontaneous fermentation on phenolic and antioxidant profiles of selected aromatic plant extracts

Abstract This study compares the effect of spontaneous fermentation of plant material as a sample pretreatment on the phenolic and antioxidant profiles in extracts by analyzing their high-performance thin-layer chromatography fingerprints. Ethyl acetate extracts from fermented and nonfermented fig leaves, lemon myrtle leaves, olive leaves and olive flowers, rosemary leaves, common sage and white sage leaves were prepared. The chromatographic fingerprints of phenolic compounds were examined in ferric chloride chelating assay and antioxidants in a 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical assay. The most distinctive changes in fingerprints between fermented and nonfermented extracts are observed in the middle part of the chromatograms from R F = 0.2‒0.5, corresponding to the R F values of phenolic acids such as rosmarinic, caffeic, coumaric, and maslinic acids. Antioxidant activity was increased in all extracts except in lemon myrtle leaf extract. Lemon myrtle leaves contain the highest amount of citral (> 90%) of any plant known in the world. Citral, the primary compound responsible for lemon myrtle’s antioxidant activity, degrades in acidic environments during fermentation. The highest increase in the antioxidant activity was measured in rosemary leaf extract (by 3.5 times), fig leaf extract (by 3 times), and in the olive flower extract (by 2.5 times).