Analysis of antioxidant properties of extracts of medicinal plants and their mixtures

Abstract

Many science publications about various medicinal plants usually characterize one or a few plants separately, but none of them evaluate how these popular and widely used plants affect each other. The purpose of this research was to determine the total amounts of secondary metabolites in separate medicinal plants and their mixtures by spectrophotometric methods. In addition, elemental analysis of these separate plants was carried out. Seven medicinal plants were analysed: leaves of peppermint (Mentha piperita L.), lemon balm (Melissa officinalis L.) and raspberry (Rubus idaeus L.), thyme (Thymus vulgaris L.) herb, blossoms of chamomile (Matricaria recutita L.), seeds of caraway (Carum carvi L.) and rose hips (Rosa L.). All these plants were grown in the Kaunas Botanical Garden of Vytautas Magnus University. The three mixtures of plants were made parallel to the three Lithuanian commercial ETNO teas (JSC Švenčionių Vaistažolės). Spectrophotometric assays (evaluating total phenolic compounds content, total flavonoid content and antiradical activity) with separate medicinal plants showed that the highest total amount of phenolic compounds was found in peppermint leaves (242.36 mg rutin equivalents (RE)/g of dry plant material), the lowest – in the seeds of caraway (22.85 mg RE/g of dry plant material). The highest and lowest total flavonoid contents were detected in peppermint and in rose hips, i.e. 97.49 and 0.78 mg RE/g of dry plant material, respectively. The highest radical scavenging activity was in the leaves of peppermint and lemon balm (291.30 and 289.71 mg RE/g of dry plant material, respectively), while caraway seeds showed the lowest activity (18.54 mg RE/g of dry plant material). All of the herbal mixtures showed the synergistic effect of phenolic compounds, while the interaction of flavonoids was rather more antagonistic.[...]