In vitro anti-inflammatory, in silico molecular docking and molecular dynamics simulation of oleanane-type triterpenes from aerial parts of Mussaenda recurvata

Bioactive-guided investigation of the aerial parts of Mussaenda recurvata Naiki, Tagane, and Yahara (Rubiaceae) led to the isolation of four triterpenes, including two new triterpenes recurvatanes A and B (1 and 2), along with two known compounds 3β,6β,23-trihydroxyolean-12-en-28-oic acid (3) and 3β,6β,19α,23-tetrahydroxyolean-12-en-28-oic acid (4). The chemical structures of the compounds were identified from spectroscopic data and by comparison with the literature. A comprehensive review of NMR data of the oleanane-type triterpenes bearing 3-hydroxy and 4-hydroxymethylene groups indicated the characteristic spectroscopic features in this series. Compounds 1–4 were evaluated for the inhibitory NO production in LPS-stimulated RAW264.7 cells. Compounds 2 and 3 showed a moderate reduction of nitrite accumulation with IC(50) values of 55.63 ± 2.52 and 60.08 ± 3.17 μM, respectively. Molecular docking model dedicated to compound 3 or pose 420, which is the best candidate among docking poses of compounds 1–4 interacted well with the crystal structure of enzyme 4WCU: PDB. The best ligand molecule, pose 420 in terms of binding energy obtained from docking studies on molecular dynamics (MD) simulations for 100 ns exhibited non-bonding interactions with the protein and remained stable inside the active site.