Alphonsea elliptica (Hook.f. and Thomson) methanol leaves extract obliterates inflammatory processes in LPS-induced human plasma

Abstract

In our previous findings, the methanol extract of A. elliptica (MEL) exhibited platelet-activating factor inhibition, indicating possible anti-inflammatory properties. Despite its ethnopharmacological significance, no studies have thoroughly investigated its anti-inflammatory potential. Based on our preliminary findings, we hypothesised that MEL might exert anti-inflammatory effects by modulating key inflammatory mediators, such as prostaglandin E2 (PGE2), cyclooxygenase-2 (COX-2), and pro-inflammatory cytokines (IL-1β and IL-6). The cytotoxicity of MEL was assessed on peripheral blood mononuclear cells (PBMCs) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In vitro, anti-inflammatory activity was investigated in lipopolysaccharide (LPS)-induced human plasma through an enzyme-linked immunosorbent assay (ELISA) and a radioimmunoassay. In addition, the phytochemical profile of MEL was characterised using LC-ESI-MS/MS spectrometry. The extract demonstrated no cytotoxic effects at 20 μg/mL concentrations. MEL exhibited significant anti-inflammatory activity, with notable inhibition of PGE2 (76.18%) and COX-2 (80.12%), as well as pronounced reductions in IL-1β and IL-6 levels, corresponding to 11.6-fold and ninefold decreases at 10 μg/mL, respectively. Concentration-dependent effects were observed, with IC₅₀ values of 4.09, 5.81, 2.12, and 1.97 μg/mL for PGE2, COX-2, IL-1β, and IL-6, respectively. LC-ESI-MS/MS analysis revealed the presence of 30 bioactive compounds, including Gramine, Eruberin B, and Grossamide, which likely contributed to the extract's anti-inflammatory effects. In conclusion, MEL abrogated LPS-induced inflammatory responses in human plasma at non-cytotoxic concentrations, demonstrating its potential as a natural anti-inflammatory agent. Furthermore, this study is the first to report the phytochemical composition of A. elliptica leaves, providing insights into its bioactive constituents and therapeutic potential.

Keywords: Alphonsea elliptica; Annonaceae; Cyclooxygenase-2; Inflammation; Inflammatory cytokines; Prostaglandin E2.