Antioxidant activity of some selected medicinal plants of family Rubiaceae and Acanthaceae using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay

Abstract

Antioxidants play an important role in reducing oxidative damage to tissues, thus associate in preventing many diseases. The present study was carried out to determine antioxidant activity of the aqueous extracts of some selected plants belonging to the family of 𝘙𝘶𝘣𝘪𝘢𝘤𝘦𝘢𝘦 and 𝘈𝘤𝘢𝘯𝘵𝘩𝘢𝘤𝘦𝘢𝘦, which are used to treat various diseases in traditional and ayurvedic medicine. Different parts of 𝘖𝘱𝘩𝘪𝘰𝘳𝘳𝘩𝘪𝘻𝘢 𝘳𝘶𝘨𝘰𝘴𝘢 (leaves, stems, roots and flowers), 𝘕𝘢𝘶𝘤𝘭𝘦𝘢 𝘰𝘳𝘪𝘦𝘯𝘵𝘢𝘭𝘪𝘴 (leaves, stems, roots, mature and immature fruits), 𝘗𝘢𝘷𝘦𝘵𝘵𝘢 𝘪𝘯𝘥𝘪𝘤𝘢, 𝘔𝘰𝘳𝘪𝘯𝘥𝘢 𝘵𝘪𝘯𝘤𝘵𝘰𝘳𝘪𝘢 and 𝘑𝘶𝘴𝘵𝘢𝘤𝘪𝘢 𝘢𝘥𝘢𝘵𝘩𝘰𝘥𝘢 (leaves, stems and roots) were collected and used from various locations of Sri Lanka in the months of May and June, 2012. Plant material was freeze dried and the powder was suspended in distilled water, subjected to microwave radiation and sonicated to prepare the aqueous extract. Antioxidant activity was determined by 1, 1Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Highest (lowest EC₅₀ value) and lowest antioxidant activities (highest EC₅₀ value) were observed in 𝘖𝘱𝘩𝘪𝘰𝘳𝘳𝘩𝘪𝘻𝘢 𝘳𝘶𝘨𝘰𝘴𝘢 leaves (38.6 ± 1.4μg/ml) and 𝘔𝘰𝘳𝘪𝘯𝘥𝘢 𝘵𝘪𝘯𝘤𝘵𝘰𝘳𝘪𝘢 stems (5.9 ± 1.5 mg/ml), respectively. The EC₅₀ value (reverse order of anti-oxidant activity), which is the concentration of compound which induces a response half way between the minimum and maximum concentration after an exposure time, for different parts of the plants showed a value less than 150 μg/ml. The values in descending order of Antioxidant activity was; 𝘖𝘱𝘩𝘪𝘰𝘳𝘳𝘩𝘪𝘻𝘢 𝘳𝘶𝘨𝘰𝘴𝘢 leaves >𝘖𝘱𝘩𝘪𝘰𝘳𝘳𝘩𝘪𝘻𝘢 𝘳𝘶𝘨𝘰𝘴𝘢 roots > Mature fruits of 𝘕𝘢𝘶𝘤𝘭𝘦𝘢 𝘰𝘳𝘪𝘦𝘯𝘵𝘢𝘭𝘪𝘴 > 𝘖𝘱𝘩𝘪𝘰𝘳𝘳𝘩𝘪𝘻𝘢 𝘳𝘶𝘨𝘰𝘴𝘢 flowers > 𝘗𝘢𝘷𝘦𝘵𝘵𝘢 𝘪𝘯𝘥𝘪𝘤𝘢 leaves > 𝘕𝘢𝘶𝘤𝘭𝘦𝘢 𝘰𝘳𝘪𝘦𝘯𝘵𝘢𝘭𝘪𝘴 leaves. 𝘕𝘢𝘶𝘤𝘭𝘦𝘢 𝘰𝘳𝘪𝘦𝘯𝘵𝘢𝘭𝘪𝘴 could also be considered to be possessing good anti oxidant activity. The differences in the antioxidant activities might be due to different compounds present in different parts of the plant, species variation, environmental temperature, amount of rainfall, availability of water and nature of soil. Among the plants studied, leaves and roots of 𝘖𝘱𝘩𝘪𝘰𝘳𝘳𝘩𝘪𝘻𝘢 𝘳𝘶𝘨𝘰𝘴𝘢 showed the highest antioxidant activity compared to the other plants used in this study.