Bioactivity assessment of methanolic extract of Rhododendron cowanianum: An endemic species of Nepal

A BSTRACT Rhododendron cowanianum is an endemic shrub of Nepal. This study investigated the phytochemical profile along with the antioxidant, antimicrobial, and cytotoxic properties of its methanolic extract. Qualitative phytochemical screening showed the presence of alkaloids, phenols, flavonoids, tannins, terpenoids, steroids, and carbohydrates. Quantitatively, the extract contained 105.4 ± 3.42 mg gallic acid equivalent/g of phenolics and 881.2 ± 5.70 mg quercetin equivalent/g of flavonoids. The extract showed the antioxidant IC 50 values of 97.77 μg/mL and 39.63 μg/mL by 2,2-diphenyl-1-picrylhydrazyl and 2,2’- azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) methods. It showed the zones of inhibition of 19.0 mm, 19.33 mm, 14.83 mm, and 10.67 mm and minimum inhibitory concentrations of 156.25 μg/mL, 312.5 μg/mL, 156.25 μg/mL, and 312.5 μg/mL against Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus , and Salmonella enterica , respectively. The minimum bactericidal concentration for S. enterica was 1.25 mg/mL and 0.625 mg/mL for the other three strains. The high-resolution liquid chromatography-mass spectrometry profiling of crude extract identified diverse classes of bioactive compounds, including lucidenic acid A, isopimaric acid, euphorin, and ganoderic acid F, which are linked with different pharmacological properties. This study profiles the phytochemicals of R. cowanianum and integrates them with bioactivity, highlighting its potential as a medicinal plant.