Background/Objectives: Hypericum perforatum L. (St. John’s Wort) is extensively utilized in ethnopharmacology due to its anti-inflammatory and immunomodulatory properties. However, its effects on the interaction between innate immunity and oxidative homeostasis remain incompletely characterized, particularly in alternative invertebrate models. This study aimed to evaluate the effects of H. perforatum extract on oxidative homeostasis and protein metabolism using the Galleria mellonella model, a 3R-compliant and ethically sustainable platform for preliminary immunological and redox-related screening. Methods: Last instar G. mellonella larvae were administered increasing concentrations of H. perforatum extract (0.001–20 mg mL−1) by intrahemocoelic injection. After 24 h, hemolymph samples were analyzed for total protein (TP), total hemocyte count (THC), encapsulation and melanization responses, superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) levels. The phytochemical profile of the extract was additionally evaluated using GC–MS analysis. Results: Significant group-dependent alterations were observed in TP levels and THC values, with the HP-2 group demonstrating the highest hemocyte counts and enhanced strong encapsulation responses. Higher extract concentrations, particularly HP-4, were associated with increased weak encapsulation profiles, suggesting altered cellular immune organization. Melanization responses became significantly elevated at 24 h following treatment. In contrast, SOD activity, CAT activity, and MDA levels did not differ significantly among groups, indicating preservation of oxidative homeostasis under the tested conditions. Conclusions: H. perforatum extract induced dose-dependent modulation of cellular and humoral immune responses in G. mellonella without evidence of detectable oxidative disruption during acute exposure. These findings support the utility of the G. mellonella model for preliminary evaluation of botanical immunomodulators and suggest that H. perforatum may influence immunophysiological pathways independently of overt oxidative toxicity.
Battal et al. (Sun,) studied this question.