Phytochemical Screening, antimicrobial and antioxidant efficacy of some plant extracts and their mixtures

Abstract

Various phytochemicals and bioactive compounds are sourced from medicinal plants. This study focused on finding the most potent plant extracts whose combination could exhibit better antioxidant and antimicrobial activities compared to the efficacy of the individual extracts. The combined plant extracts were O. stamineus, E. longifolia, A. bilimbi, P. granatum, and M. nigra. Ultrasound extraction technique was used for the extraction of the plant material before screening the extracts for the presence of several phytochemical groups. After the screening for the presence of phytochemicals, the extracts were evaluated for antimicrobial activity against five microorganisms (S. aureus, B. subtilis, P. vulgaris, E. coli, and C. albicans) at 3 different concentrations (600, 400 and 200 mg/mL) using disc diffusion method. The aim of this antimicrobial screening was to identify and select the most potent extracts for the combination study. From the screening result, P. ganatum and M. nigra had the highest antimicrobial activity against all the tested organisms, as well as the highest DPPH radical scavenging activity of 95.40 % (IC50 = 120.2 μg/mL) and 90.20 % (IC50 = 330.0 μg/mL), respectively. Hence, both extracts were combined and screened for antimicrobial and antioxidant activities at the same concentration range but at different combination ratios of 1:1, 1:2 and 2:1 (v/v). The results showed the extract mixtures at different combination ratios of 1:1, 1:2 and 2:1 (v/v) to exhibit good antioxidant and antimicrobial activities. However, the combination ratio of 1:1 gave the best antioxidant activity as it achieved an IC50 value of 82.0 μg/mL. Therefore, it is concluded that the mixture of the selected extracts exhibited strong antioxidant and antimicrobial activities, coupled with a significant level of antifungal activity.