COMPARATIVE EVALUATION OF ANTIOXIDANT ACTIVITY AND PHENOLIC CONTENT IN LAMIACEAE SPECIES DEPENDING ON THE ECOLOGICAL CONDITIONS OF EAST KAZAKHSTAN

Abstract

This study investigates the antioxidant activity and phenolic content of Lamiaceae species cultivated under the ecological conditions of East Kazakhstan. Three species traditionally used in folk medicine and the food industry were selected as objects of study: Mentha longifolia, Melissa officinalis, and Ocimum basilicum. For the first time, a comprehensive comparative evaluation of their biological activity was conducted with consideration of the region’s ecological factors, including high solar radiation, continental climate, and daily temperature fluctuations, which may significantly influence the phytochemical composition of plants.

The research methods included spectrophotometric determination of antioxidant activity using the DPPH radical and colorimetric quantification of phenolic compounds by the Folin–Ciocalteu method. Both fresh and dried plant samples were analyzed to determine the effect of processing on the preservation of bioactive components. The results demonstrated that fresh leaves exhibited higher antioxidant activity compared to dried samples. The most pronounced effect was observed in Ocimum basilicum, where IC₅₀ decreased from 30.1 to 21.1 μg/ml. The highest activity was recorded in Mentha longifolia (IC₅₀ 16.3–17.1 μg/ml). A strong negative correlation between phenolic content and antioxidant activity (r = –0.96…–0.98) confirmed the leading role of phenolic compounds in antioxidant mechanisms.

The findings highlight the considerable potential of Lamiaceae species grown in East Kazakhstan as a source of raw material for pharmaceutical and food industries. The novelty of this research lies in revealing the regional specificity of phenolic accumulation and demonstrating the importance of fresh plant material for maintaining maximum biological activity. These results provide a basis for further studies focused on optimizing extraction methods and identifying the individual composition of bioactive compounds.

Keywords: Lamiaceae; antioxidant activity; phenolic compounds; fresh and dried samples; East Kazakhstan.