Phytochemical investigation, in vitro antioxidant, antibacterial activities of the leaf and fruit extracts of Hypericum revolutum Vahl (Amija), and essential oil composition of the leaf extract

Hypericum revolutum Vahl, a flowering plant in the Hypericaceae family, is traditionally used in Ethiopia to treat febrile illnesses in humans and combat diarrhea in livestock. It is known for its significant analgesic and anti-inflammatory activities. This study aims to investigate the phytochemical composition, antioxidant activity, and antibacterial efficacy of the leaf and fruit extracts, as well as the essential oil obtained from the leaves. Essential oil was extracted by hydrodistillation, while crude extracts were obtained through successive maceration using petroleum ether, chloroform, and methanol solvents. Gas chromatography-mass spectrometry (GC-MS) analysis identified major compounds, including 1R-alpha-Pinene (59.21%) and D-Limonene (7.979%). Phytochemical screening of methanol extracts revealed the presence of flavonoids, phenols, tannins, saponins, and alkaloids. Quantitative analysis revealed high total phenolic (162.04 ± 0.77 mg gallic acid equivalents (GAE)/g) and total flavonoid content (181.96 ± 8.35 mg of quercetin equivalents (QE)/g) in fruit and leaf extracts, respectively. Antioxidant activity, assessed by the DPPH assay, showed IC₅₀ values of 110.07 ± 1.60 μg/mL (fruit) and 154.97 ± 4.34 μg/mL (leaf) in methanol extracts, compared to ascorbic acid (IC₅₀: 27.54 ± 0.80 μg/mL). The FRAP assay revealed higher absorbance in extracts compared to ascorbic acid, indicating potent antioxidant potential. Antibacterial activity, assessed using the agar-well diffusion method, revealed significant inhibition against gram-negative (E. coli, P. aeruginosa, K. pneumoniae) and gram-positive bacteria (S. aureus, S. pneumoniae), with leaf extracts showing superior activity. The essential oil exhibited lower antibacterial efficacy. These findings support the traditional medicinal uses of H. revolutum and suggest its potential as a natural source of antioxidant and antibacterial agents. Further studies, including MIC/MBC determinations and advanced phytochemical analyses such as LC-MS/MS or HPLC-MS, are warranted to fully explore its therapeutic potential.