Rhoifolin loaded in PLGA nanoparticles alleviates oxidative stress and inflammation in vitro and in vivo

Rhoifolin (ROF) is a bioactive plant flavonoid with potent antioxidant and anti-inflammatory activity. However, no delivery system has yet been developed for ROF to overcome its biopharmaceutical limitations. The purpose of this study was to design a ROF-loaded polymeric nanocarrier as a potential anti-inflammatory nanomedicine. ROF was isolated from Jordanian Teucrium polium L. and entrapped into poly(lactide-co-glycolide) nanoparticles (PLGA NPs), followed by tannic acid-mediated surface modification with poly(ethylene glycol) (PEG). The optimal ROF NPs were highly monodisperse with an average diameter of 204 nm, a zeta potential of -28 mV, an entrapment efficiency of 45%, and drug loading of 9% w/w. The NPs exhibited excellent colloidal stability during storage and in the presence of serum and achieved sustained drug release for up to 96 h at physiologic (7.4) and acidic pH (5.0). In vitro cell-free antioxidant assays confirmed the potent radical scavenging activity of free ROF and ROF NPs. Moreover, ROF NPs were superior to free ROF in relieving oxidative stress in stimulated RAW 264.7 murine macrophages, which was attributed to enhanced cellular uptake of the NPs as confirmed by confocal microscopy and fluorimetry. In vivo anti-inflammatory activity was evaluated in a formalin-induced rat paw edema model. The results showed that ROF NPs were superior to free ROF in mitigating the histopathological changes in the inflamed paw tissues. Moreover, the NPs were equally potent to free ROF and the nonsteroidal anti-inflammatory drug diclofenac in terms of inhibiting the increase in paw thickness, normalizing nitric oxide levels, and modulating the gene expression of pro-inflammatory cytokines in the inflamed paw tissues. Our findings present a promising nanocarrier platform that can enhance the solubility and control the release of ROF, which will facilitate its administration in the treatment of inflammatory diseases.