This study was aimed at investigating the anti-plasmodial and antioxidant activities of the extract of the leaf of Lophira lanceolata, a traditional medicine recipe. The methanol extract (ME) obtained by 72 h cold maceration was evaluated for acute toxicity test (LD50) and phytochemical constituents. The suppressive and curative anti-plasmodial activities of the extract were investigated using rodent malaria model. Mice (20 to 34 g) infected with 1 × 107 Plasmodium berghei parasitized red blood cell were used to test for suppressive and curative anti-plasmodial activities after oral administration of ME (100, 200 and 400 mg/kg) for four and seven days, respectively. The preliminary antioxidant activity of the extract (25, 50, 100, 200 and 400 μg/ml) was evaluated using in vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging, hydrogen peroxide scavenging and reducing (power) ability assays. The methanol leaf extract of L. lanceolata exhibited a dose-dependent suppression of parasitaemia up to 100% suppression at 400 mg/kg. The suppression produced by the extract was significantly (P< 0.05) higher than the chemo suppression produced by 20 mg/kg chloroquine (50.90%). Similarly, the extract at the same doses (100, 200 and 400 mg/kg) exhibited significant (P<0.05) but non-dose-related decreases in parasitaemia in the curative model (60.90, 54.69 and 79.69%) which was comparable to the 82.80% decrease caused by chloroquine (20 mg/kg). Phytochemical studies revealed the presence of flavonoids, alkaloids, oils, saponins, glycosides, carbohydrates, acidic compounds, terpenoids and reducing sugar. The LD50 test caused no deaths in the treated mice up to 5,000 mg/kg body weight. The DPPH assay, for free radical scavenging effect of the methanol extract was significant (P<0.001) as the concentration increases. Hydrogen peroxide scavenging and reducing power assays showed concentration-dependent and significant (P<0.05) results. These findings suggest that methanolic extract of the leaf of L. lanceolata is safe up to a dose of 5,000 mg/kg body weight and possesses anti-plasmodial and anti-oxidant activities.
Key words: Lophira lanceolata, anti-plasmodial, anti-oxidant, plasmodium berghei, DPPH, hydrogen peroxide, albino mice.
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