Analysis of flavonoids and phenolic acids in Greek aromatic plants: Investigation of their antioxidant capacity and antimicrobial activity

The phenolic fraction of plant extracts has been linked to their antioxidant capacity and antimicrobial activity. In the present paper, RP-HPLC with UV detection was employed to distinguish phenolic compounds from the other constituents of the plants examined. The phenolic substances were identified and quantified after comparison with reference standards. A GC–MS method is also presented for characterization of different phenolics as trimethylsilyl derivatives. The antioxidant capacity was determined, in dried plants and in their methanol extracts, with the Rancimat test using sunflower oil as substrate. Both pulverized plants and extracts showed antioxidant capacity. Total phenolic content in the extracts was determined spectrometrically applying the Folin-Ciocalteu assay. It ranged from 2.9 to 28.2 mg gallic acid/100 g dry sample. Antimicrobial activity of the extracts against selected microorganisms was also investigated.