THE APPRAISAL OF ANTIOXIDANT PROPERTIES OF Citrus hystrix LEAF EXTRACT AND ITS ANTIBACTERIAL ACTIVITY AGAINST TWO PLANT PATHOGEN BACTERIA

Abstract

The Citrus hystrix tree, known as the kaffir lime, is a small tropical evergreen plant with a strong citrus scent and a wide range of bioactivities.  This study aimed to determine the antioxidant properties of C. hystrix leaf extracts and their antibacterial activity against two plant pathogenic bacteria, namely Erwinia chrysanthemi and Erwinia carotovora. The antioxidant activity was evaluated through a DPPH dot blot assay and DPPH radical scavenging activity with 2,2-diphenyl-1-picrylhydrazyl (DPPH) serving as the radical. The Kirby-Bauer disc diffusion method was selected to evaluate antibacterial properties. The leaves of C. hystrix were consecutively soaked in hexane, ethyl acetate, and methanol to obtain crude extracts. Based on the DPPH dot blot assay, the lowest concentration of the extract that started to scavenge the DPPH radical was at 0.012 mg/mL. According to the DPPH radical scavenging method, all extracts showed promising antioxidant activity in a concentration-dependent manner. The ethyl acetate extract exhibited the highest percentage activity at 83%. The IC50 value of 125.732 μg/mL was recorded for the ethyl acetate extract of C. hystrix leaves, which led to promising antioxidant activity to scavenge 50% DPPH radicals. In antibacterial activity, E. carotovora was more susceptible towards all extracts compared to E. chrysanthemi. The ethyl acetate extract was found to be the most active antibacterial agent with an inhibition zone of 20.67 mm. Therefore, C. hystrix can be regarded as a prospective source of both antioxidants and antibacterial agents, which is crucial as the foundation for scientific data used in the pharmaceutical industry, as well as a plant-based antibacterial agent in the agricultural industrial sector.