Characterization of Citrus aurantifolia Swingle (Fam. Rutaceae) Fruit Extracts with Antibacterial Activity

Abstract

Background: In the Philippines, the use of herbal medicines as remedy for diseases is still common; among these is Citrus aurantifolia Swingle (Fam. Rutaceae), which was proven to have antibacterial property in another study. Since antimicrobial resistance is currently one of the major health issues globally, this study provided an opportunity in the discovery of new antimicrobials.

Objectives: This study aimed to isolate and characterize the fractions responsible for the antibacterial activity of C. aurantifolia extracts.

Methods: The manually expressed juice was lyophilized, while a small portion was phytochemically screened. The extract was subjected to Kupchan partitioning using water, ethyl acetate (EtAc), and dichloromethane (DCM) as solvents. The fractions were tested against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Proteus vulgaris for antibacterial properties. Thin layer chromatography (TLC) and bioautography were then conducted on the active fraction.

Results: The crude extract tested positive for plant acids, glycosides, and flavonoids. Among the three fractions, the EtAc fraction exhibited the largest zones of inhibition (mm) at 18.67±0.58, 17.33±1.15, 10.00±1.00, and 15.33±1.53 for S.a., B.s., E.c., and P.v., respectively. The appropriate solvent system was found to be ethyl acetate:hexane:acetic acid (5:4:1) for the TLC of both crude extract and EtAc fraction. Zones of inhibition were observed in the B.s. culture around the upper spots in the chromatogram.

Conclusion: Ethyl acetate can be used to extract the antibacterial components of C. aurantifolia fruit. A midpolar compound with a possible flavonoid character is responsible for its activity. Other chromatographic and spectroscopic techniques are recommended to isolate and identify the active compound.