The Antioxidant and Anti-Inflammatory Properties of Merremia umbellata Extract

Merremia umbellata Hallier f. (MU) has been used as an anti-inflammatory agent to treat burns and scales. However, the potential anti-inflammatory mechanisms of action of this plant have not been elucidated. This study aimed to assess the antioxidant and anti-inflammatory effects of the leaf and shoot of MU grown in Bangladesh. The MU extract exhibited antioxidant activities as demonstrated by DPPH and ABTS free-radical-scavenging activities and the total polyphenol and total flavonoid contents. MU extract significantly reduced the lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production in RAW264.7 macrophage. Accordingly, the gene levels of inducible NO synthase and cyclooxygenase-2 were suppressed. The MU extract alleviated the LPS-induced expression of TLR4, NF-kappa B, and inflammatory cytokines (TNF-alpha, IL-6, and IL-1 beta). The constituents of a MU extract were tentatively identified using UHPLC-PDA-QTOF/MS techniques. The main compounds were identified as 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, quercitrin, and 4,5-dicaffeoylquinic acid. Molecular docking analysis revealed that these compounds interact with TLR4 protein, with quercitrin showing the highest binding affinity among them. Overall, our findings demonstrate the antioxidant and in vitro anti-inflammatory activities of MU and its potential compounds to target the TLR4-NF-kappa B signaling pathway. These findings are potentially used to further explore promising natural food ingredients that are effective in regulating inflammation.