Inhibitory Potential of Pulutan (Urena lobata) Leaf Extract on Inducible Nitric Oxide Synthase as Anti-inflammatory Agent: In Vitro and In Silico Approaches

Urena lobata is an herbal remedy traditionally used to cure certain ailments. Its flavonoid and phenol-rich content has been shown to have free radical scavenging activity. Nitric oxide (NO) is an active gaseous substance that is released by cells and plays a role in inflammation. This study examined the ability of U. lobata leaf extract to induce NO production and suppress inducible NO synthase (iNOS). The leaves of U. lobata were extracted with ethanol. The phytoconstituents of the extract were identified, their physicochemical and pharmacokinetic properties were predicted, and their anti-inflammatory activity was evaluated. The structures of the phytoconstituents were determined using the molecular docking approach. Griess technique was used to evaluate NO generation in IL-1β-treated hepatocyte culture media containing the extract. An in silico approach was employed to investigate the suppression of iNOS by phytoconstituents from U. lobata. The results showed that stigmasterol and gossypetin were identified in the extract and had a strong inhibitory effect on iNOS based on the inhibition constant. However, it has lower potency than β-sitosterol. The ethanol extract of U. lobata (IC50 = 163.03 µg/mL) had a lower potency than gossypin (IC50 = 100.31 µg/mL) but was comparable to gossypetin (IC50 = 164.18 µg/mL) for inhibiting NO generation. The ethanol extract of U. lobata demonstrated anti-inflammatory action by lowering NO level, but at a lower concentration than gossypin and gossypetin. The study revealed that U. lobata ethanol extract inhibited NO production through active substances, like gossypetin, mangiferin, β-sitosterol, and stigmasterol, thereby suppressing iNOS activity.