Natural Antioxidant Constituents from Selected Aromatic Plants and Their Antimicrobial Activity Against Selected Pathogenic Microorganisms

Aromatic plants contain natural antioxidant constituents such as phenolic compounds, which have attracted a great deal of public and scientific interest because of their health-promoting effects as antioxidants. Five plants, Filipendula ulmaria (meadow sweet), Crataegus monogyna (hawthorn), Polygonum aviculare (polygonum), Potentilla anserina (silverweed), and Pelargonium purpureum (little robin), have been examined in order to determine their phenolic composition. Reversed-phase high performance liquid chromatography (RP-HPLC) was employed for the identification and quantification of phenolic compounds of the aforementioned plants. Gas chromatography–mass spectrometry method (GC-MS) was also used for identification of phenolic compounds after silylation. Analysis of the non-volatile and thermolabile phenolic compounds by GC-MS presupposes their conversion into volatile and thermotolerant derivatives. The derivatization process was optimized against reagents, temperature and reaction time. 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 and it ranged from 7.2 to 28.2 gallic acid equivalents (GAE)/(mg/mL). Antimicrobial activity of the extracts against selected microorganisms was performed using the disk diffusion method. Gram-(+) bacteria were more sensitive to the plant extracts than Gram-(–) bacteria.