Antioxidant, analgesic, anti-inflammatory and antipyretic properties, and toxicity studies of the aerial parts of Imperata cylindrica (L.) Beauv

Imperata cylindrica (L.) Beauv. (Poaceae family) is a perennial weed growing in tropical and subtropical areas and it is used in several herbal preparations to treat specific pathologic factors inducing pain. This work aimed to determine the in vitro antioxidant and in vivo anti-inflammatory, analgesic and antipyretic activities of the aerial parts of this plant. The methanol extract (MEIC) was used for (i) phytochemical fingerprint by High-Performance Liquid Chromatography (HPLC), (ii) total phenolic content (TPC) evaluation by the Folin-Ciocalteu colourimetric method, (iii) 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenger spectrophotometric assay, (iv) antioxidant capacity by Ferric Reducing Antioxidant Power (FRAP) assay, (v) analgesic activity evaluated with the acetic acid-induced writhing test, (vi) anti-inflammatory activity evaluation by carrageenan-induced paw oedema, (vii) antipyretic effect on lipopolysaccharide (LPS)-induced fever in rats, and (viii) acute and sub-chronic toxicity in mice. The MEIC presented an average rate of TPC (1920.63 ± 360.62 mgGAE/100 g of dry weight (DW)), which is mostly represented by tannins (37.30%), organic acids (32.84%) and flavonols (10.88%). The DPPH free radical scavenger spectrometric assay showed the antioxidant capacity of the MEIC (IC50 = 192.07 ± 0.78 µg/mL) confirmed by the FRAP assay results (29.60 ± 0.55 mmol Fe2+/Kg of DW). The MEIC decreased significantly the number of writhing in a dose-dependent manner (p < 0.01) showing its analgesic activity; the extract inhibited the inflammation in a dose-dependent manner at the first stage (1st h, p < 0.01) and the second stage (3rd h, p < 0.001) post carrageenan induction and it demonstrated an antipyretic activity by lowering the body temperature (Tb) dose-dependently post LPS induction (i.p. route) and time-dependently at the dose of 200 mg/kg (p < 0.001) in mice. Moreover, the acute and sub-chronic toxicity in mice did not reveal any signs of toxicity and any changes in targeted biochemical and haematological parameters. The quantified phytocompounds could be at the origin of these pharmacological activities. These findings support the beneficial use of this plant to alleviate pains and fever in inflammatory or other diseases. Further studies on the isolation of the bioactive compounds and their action mechanisms should be carried out to confirm these results.