Flavonoid-enriched fraction from Echinodorus macrophyllus aqueous extract exhibits high in-vitro and in-vivo anti-inflammatory activity.

Objectives: Echinodorus macrophyllus (Kunth) Micheli (Alismataceae) is popularly used as an infusion to treat inflammatory diseases. This work fractionated the aqueous extract of E. macrophyllus (AEEm) to improve its anti-inflammatory effects.

Methods: Aqueous extract of E. macrophyllus was fractionated by Sephadex LH-20 and analysed by HPLC-DAD. Anti-inflammatory action was evaluated, in vivo, by air pouch model (total leucocyte, protein and leukotriene B (LTB )), and, in vitro, by neutrophil migration (transwell assay) and its Mac1 expression (flow cytometry), and RAW 264.7 nitric oxide (NO) production (Griess reaction).

Key Findings: Fr20 reduced total leucocyte at 2.5 mg/kg (29.7%) while ethanolic extract of E. macrophyllus (EAEm) increased it (94.0%). Fr20 showed higher (P < 0.05) inhibition (89.8%) of LTB in exudate than EAEm (75.0%). Fr20 and EAEm decreased exudate protein and inflammatory infiltrate in pouch tissues, in-vitro neutrophil migration, and NO production. Otherwise, Fr40 did not reduce leucocytes and exudate protein (until 50 mg/kg) nor tissue inflammation, and increased in-vitro NO production. The inhibition of neutrophil migration by EAEm, but not Fr20, was dependent on reduced Mac-1 expression.

Conclusions: The fractionation of AEEm provided a more potent anti-inflammatory fraction containing flavonoids (Fr20) that reduces the migration of neutrophils and LTB4 release, probably contributing to its mechanism of action.