Anti-inflammatory alkaloids from lotus (Nelumbo nucifera Gaertn.) leaves

Lotus (Nelumbo nucifera Gaertn.) is an aquatic perennial; and lotus leaves were used for food and functional herbal tea in Asia, while alkaloids are regarded as important components. Total alkaloids (TAs), phenolic alkaloids (PAs), and non-PAs from lotus leaves revealed inhibitory effects on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging effects and nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Five alkaloids were isolated and identified as asimilobine (1), roemerine (2), lysicamine (3), nuciferine (4), and N-methylcoclaurine (5). Of them, compounds 1 and 2 exhibited potency as direct NO scavengers while 5 exerted the highest DPPH radical-scavenging effect. Compound 5 also inhibited NO production with an IC₅₀ value of 6 μM through suppressing inducible NO synthase (iNOS) expression in LPS-induced RAW 264.7 macrophages. Compounds 2 and 3 inhibited NO production (IC₅₀ values of 21 and 25 μM, respectively) as well as iNOS and cyclooxygenase (COX)-2 expressions. Further, compound 5 occupied 27.5% of TAs by high-performance liquid chromatography (HPLC) analysis, which was mainly responsible for the activities. Besides, no obvious cytotoxicity was observed under treated concentrations. The present study suggests that alkaloid extracts and individual components can be valuable functional ingredients from lotus leaves.