Effects of IPassovia ovata/I Mistletoe on Pro-Inflammatory Markers In Vitro and In Vivo

New agents that can suppress inflammatory responses are being sought, since chronic inflammation is associated with several pathologies. This work aims to elucidate phytochemicals from the hydroethanolic extract of mistletoe Passovia ovata (POH) and its anti-inflammatory potential. POH is submitted to HPLC-UV, qualitative analysis of chemical constituents, and flavonoid quantification. Cytotoxicity is evaluated in RAW 264.7 macrophages by MTT. LPS-stimulated RAW 264.7 cells are treated with POH and, after 48 h, the nitrite and cytokine levels are quantified. BALB/c mice are treated by gavage with POH and stimulated with λ-carrageenan to induce paw oedema or peritonitis. POH yield is 25% with anthraquinones, tannins, anthocyanins, anthocyanidins, flavonols, catechins and flavanones present and flavonoid content of 4.44 ± 0.157 mg QE/g dry weight. POH exhibits low cytotoxicity and significantly reduced (p < 0.01) nitrite, IL-1β, IL-6, and TNF-α quantification at 500 μg/mL. POH at 500 mg/kg prevents paw edema increase and also reduces inflammatory infiltrate and mast cells in the footpad. In the peritonitis model, POH does not influence cytokines levels or cell counts. Overall, POH demonstrates a high concentration of flavonoids and prominent effects in the reduction in pro-inflammatory markers in vitro and in the inhibition of paw oedema.