Rhus Coriaria L. (Sumac) Leaves as an Antibacterial Agent

Abstract

Background Rhus coriaria L. has various medicinal effects, exhibiting antidiabetic, anti-inflammatory, anticancer, antioxidant, antiviral, anti-ischemic, hypolipidemic and antibacterial activity. Its antibacterial activity has been extensively studied, revealing terpenoids, flavonoids and hydrolysable tannins as the main active compounds. Most of these studies have been performed on fruit, and a few on leaves and seeds. Methods Extract of R. coriaria leaves was fractionated into six fractions by high-performance liquid chromatography (HPLC). Two active fractions (Rc1 and Rc2) were subfractionated into fractions Rs1–3 and Rs4–6, respectively. The active subfraction Rs5 was subjected to LCMS analysis. Antibacterial activity of the extracts was assessed by well and disk-diffusion methods, and minimal inhibitory concentration (MIC) by tetrazolium (TTC) test and minimal bactericidal concentration (MBC) by drop test were determined. Subfraction Rs5 was further incorporated into an eye drop formulation and tested for antibacterial activity, and leaf extract was also tested against the fungus Botrytis cinerea. Results Crude leaf extract, fractions Rc1 and Rc2 and subfractions Rs1–6 showed antibacterial activity, with MIC values ranging from 0.2–3.1 mg/mL and MBC values from 0.3–6.2 mg/mL, depending on the fraction and the bacteria. Subfraction Rs5 had the strongest antibacterial activity with a MIC of 0.4 mg/mL and MBC of 0.6–2 mg/mL, depending on the bacterium being tested. Rs5 incorporated into an eye drop formulation also showed antibacterial activity. The leaf extract further showed antifungal activity against the agricultural pest Botrytis cinerea. Conclusions The crude leaf extract and its fractions exhibited antibacterial and antifungal activity. The antibacterial activity increased in the fractions and subfractions of the leaf extract compared to the crude extract, suggesting enrichment of the active antibacterial compounds during purification. Leaves, which are much more readily available, and in greater quantities than fruit, throughout the year, may therefore serve as an inexpensive and effective source for an antibacterial product that can be used in the food and agricultural industries.