Antioxidant and immunomodulatory activities of the ethanolic extract of <i>Eugenia jambolana</i> Lam. root bark assessed using <i>in vitro </i>and<i> in vivo</i> methods

Introduction: Natural products are a rich source of antioxidants, effective on immunological disorders. The present study was planned to evaluate the antioxidant activity of ethanolic extract of root bark of an Indian medicinal plant, Eugenia jambolana, by in vitro methods and immunomodulatory activity by in vivo methods. Methods: The ethanolic extract of the collected root bark of E. jambolana (EJE) was prepared and tested in vitro for antioxidant activity using concentrations 10-50 µg/mL through 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and superoxide anion scavenging assays. Further, the immunomodulatory effects of EJE were assessed in animal studies against the experimental antigen, sheep RBC, through oral administration at doses of 100, 200, and 400 mg/kg, measuring its impact on antibody titer values in the antigen-antibody reaction and on paw thickness in mice (delayed-type hypersensitivity [DTH] study) to evaluate humoral and cell-mediated immune responses, respectively. Results: EJE exhibited scavenging properties against DPPH free radicals and superoxide anion with IC50 values of 43.79 ± 0.24 µg/mL and 47.64 ± 0.18 µg/mL in the respective studies. EJE at 400 mg/kg oral dose demonstrated a significant (P&lt;0.05) antibody titer value and DTH response in the in vivo immunomodulatory activity studies. These studies showed that the 400 mg/kg oral dose of EJE produced 29.36% and 39.06% immunomodulatory effects in humoral and cell-mediated immunity studies, respectively. Conclusion: The experiments of this study demonstrated the antioxidant and immunomodulatory potential of the ethanolic extract of E. jambolana root bark.