POSITIVE EFFECTS OF DROUGHT ON THE QUALITY OF AROMATIC PLANTS: IMPROVEMENT OF TOTAL PHENOLIC AND FLAVONOID CONTENTS AND TOTAL ANTIOXIDANT CAPACITY

Abstract

This study aimed to evaluate the effects of drought on the antioxidant properties and some growth parameters of mint (Mentha x piperita L.), basil (Ocimum basilicum L.), hyssop (Hyssopus officinalis L.), and oregano plants (Origanum vulgare L.). This study was carried out at the Faculty of Agriculture and Food Sciences experimental station in Sarajevo in 2024. Four water-holding capacities (WHC), namely 90% WHC, 80% WHC, 60% WHC, and 40% WFC were used as drought stress levels in this study. An experiment had a completely randomized design with three replicates and was carried out in pots in the greenhouse under controlled conditions. The total phenolic and flavonoid contents and total antioxidant capacity in the leaf extracts of the tested plants were evaluated by the Folin-Ciocalteu assay, AlCl₃ assay, and ferric reducing/antioxidant power (FRAP) assay, respectively. Drought at 60% and 40% WHC caused a decline in plant height, leaf area, and fresh and dry weight. In contrast, it increased total phenolic and flavonoid contents and total antioxidant capacity compared to plants exposed to 80% and 90% of WHC, regardless of plant species. The highest total phenolic contents (392.9 mg 100 g^-1), total flavonoid contents (219.9 mg 100 g^-1), and total antioxidant capacity through FRAP assay (3.35 mmol Fe²⁺ 100 g^-1), were observed in mint plants exposed to drought at 60% WHC. The results of this study point to the conclusion that the antioxidant properties and, thus, the quality of the studied aromatic plant species can be enhanced significantly by deliberately applying drought stress during their cultivation. However, this enhancement is usually accompanied by a decrease in plant growth. In this regard, for each particular aromatic plant species, it is necessary to carefully assess the advantages and disadvantages of the deliberate application of each drought level during cultivation.