Phytochemical, Antioxidant and Antimicrobial Evaluation of Terminalia arjuna Bark Extracts

Abstract

The present study evaluated the phytochemical composition, antioxidant potential, antimicrobial activity, and GC–MS profile of bark extracts of Terminalia arjuna prepared using solvents of different polaritiesBark samples were collected from J.S. Murarka Multiple Campus, Lahan, Nepal, and extracted using methanol, ethanol, hexane, and dichloromethane (DCM) by the maceration method. Preliminary phytochemical screening was performed using standard qualitative tests, while total phenolic content (TPC) and total flavonoid content (TFC) were quantified using the Folin–Ciocalteu and aluminium chloride methods, respectively. Antioxidant activity was determined using the DPPH radical scavenging assay, and antimicrobial activity was evaluated against Staphylococcus aureus, Shigella sonnei, Klebsiella pneumoniae, and Escherichia coli using the agar well diffusion method. All experiments were conducted in triplicate and analyzed using one-way ANOVA (p < 0.05). Qualitative screening revealed the presence of phenols, flavonoids, alkaloids, terpenoids, and glycosides, particularly in polar solvent extracts. Quantitative analysis showed that the ethanolic extract contained the highest total phenolic content (329 mg GAE/g) and total flavonoid content (129 mg QE/g). In the DPPH assay, strong antioxidant activity was observed for the methanol extract (IC₅₀ = 6.34 µg/mL) followed by ethanol extract (IC₅₀ = 7.76 µg/mL), whereas hexane (IC₅₀ = 25.63 µg/mL) and dichloromethane (IC₅₀ = 15 µg/mL) showed comparatively weaker antioxidant activity. Antimicrobial testing showed that the ethanolic extract produced the highest inhibition zones (10–12 mm) against the tested bacterial strains. GC–MS analysis of the ethanol extract identified several bioactive compounds, including α-pinene, limonene, 1,8-cineole, terpinen-4-ol, caryophyllene, hexadecanoic acid, phytol, linoleic acid, and oleic acid. The results demonstrate that Terminalia arjuna bark is a rich source of bioactive phytochemicals with significant antioxidant and antibacterial activities, particularly when extracted with ethanol. These findings support the traditional medicinal use of the plant and highlight its potential for further bioactive compound isolation and pharmacological applications.