Phytochemical Profile, Antioxidants, Bioactive Compounds, and Antibacterial Activity of a Bangladeshi Commercial Green Tea (Camellia sinensis L.) Extract: A Correlative Investigation Using in vitro and in silico Approaches

Tea (Camellia sinensis), a widely consumed beverage, reduces oxidative stress and has antimicrobial properties due to its phytochemicals. Ethanolic extracts from Bangladeshi green tea were analyzed for phytochemicals, antioxidants, bioactive compounds, and antibacterial activity using in vitro and in silico methods. Qualitative screening detected alkaloids, phenolics, flavonoids, and tannins, with total phenolic content (TPC) at 35.95 ± 0.24 mg GAE/g and total flavonoid content (TFC) at 34.61 ± 1.53 mg QE/g. Antioxidant tests showed strong total antioxidant capacity (301.01 ± 14.32 mg AAE/g) and DPPH radical scavenging (IC50 2.70 μg/mL vs. ascorbic acid’s 3.75 μg/mL). HPLC identified gallic acid and vanillic acid as key compounds. Agar well diffusion assays revealed dose-dependent zones of inhibition against Staphylococcus aureus (12–22 mm) and Escherichia coli (10–20 mm) at concentrations of 25–200 mg/mL. In silico docking showed gallic and vanillic acids binding to S. aureus (PBP2a, SrtA) and E. coli (AmpC β-lactamase, GyrB) targets with affinities of -4.9 to -6.0 kcal/mol, stabilized by hydrogen bonds and π-interactions. ADME profiles indicated high gastrointestinal absorption, Lipinski compliance, and bioavailability (0.56–0.85). Toxicity predictions suggested minimal risks, mainly nephrotoxicity. PASS analysis predicted antibacterial, β-lactamase, and DNA gyrase inhibition activities. These findings underscore Bangladeshi green tea as a promising source of antioxidants and antibacterials for oxidative stress and infections.