Antifungal, antibacterial, and AChE inhibitory activity of the alkaloid mixture of Holarrhena mitis (Vahl) R.Br. ex Roem. & Schult (Kirimawara)

Abstract

The scarcity of novel drugs has prompted scientific research to re-evaluate natural products as drug lead compounds with high chemical and biological potential. Among the many phytochemicals, alkaloids are an important group of natural products consisting of an extensive list of bioactivities such as antitumor, anti-inflammatory, antiviral, antihypertensive, antiulcer, diuretic and analgesic. The alkaloid mixture from the bark of Holarrhena mitis, which is an endemic plant to Sri Lanka, consists of 11 known compounds. This alkaloid mixture was assessed for its antibacterial, antifungal, antioxidant and acetylcholinesterase (AChE) inhibitory activities and brine shrimp lethality. Significant antifungal activity against standard strains of five Candida sp. mainly against C. krusei and C. glabrata, with inhibition diameter of 21 mm was identified. In addition, it showed moderate antibacterial activity (MIC 6.7±0.1 mg mL-1) against both Escherichia coli and Staphylococcus aureus, and AChE inhibitory activity (IC50 value of 58±0.5 μg mL-1) and non-toxicity to brine shrimp lethality assay (LC50 value of 1410.11±2.05 mg L-1). However, the alkaloid mixture did not exhibit potential antioxidant activity (IC50 399±1.3 mg L-1). These empirical results suggest that alkaloids isolated from this plant could be good potential candidates for further development of new antifungal and antibacterial lead compounds, and AChE inhibitors.