Psychoserpens A and B: Two New Iridoids From the Leaves of <i>Psychotria serpens</i> L. That Inhibit Nitric Oxide Production

Psychotria serpens, a significant traditional Vietnamese plant, exhibits anti-inflammatory properties and is clinically used to treat rheumatism and sciatica. However, its bioactive components remain poorly understood. In this study, phytochemical investigation of P. serpens leaves led to the isolation and structural elucidation of eight iridoid glucosides (1-8), including two previously undescribed compounds, psychoserpen A (1) and B (2). Their structures were elucidated by a combination of IR, HRESIMS, and 1D- and 2D-nuclear magnetic resonance (NMR) analyses. This is the first report of compounds 4, 7, and 8 from the genus Psychotria and compounds 3, 5, and 6 from P. serpens species. All the isolated compounds significantly inhibited nitric oxide (NO) production on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage with IC₅₀ values ranging from 27.2 to 61.4 µM.