Abstract
Extracts of Alstonia boonei and Carica papaya are used in herbal medicine for the treatment of malaria. This work investigated the phytochemical, antioxidant, and antimalarial effects of hydromethanolic extracts of Alstonia boonei and Carica papaya. A four-day chemosuppressive test was conducted to assess the ability of the extracts to prevent establishment of infection. Three doses of the extracts were administered—100, 200, and 400 mg/kg bw—prior to Plasmodium berghei challenge. Change in body weight, parasitemia, packed cell volume (PCV), and mean survival time was determined. A three-day curative test was also carried out on Plasmodium berghei-infected mice to determine the effects of the plant extracts (200 mg/kg bw) on parasitemia and biochemical indices of liver and kidney functions, lipid metabolism, and oxidative stress. The study revealed that the extracts possessed phenolic compounds (34.13 ± 1.90 mg GAE/g for Alstonia boonei and 27.99 ± 1.46 mg GAE/g for Carica papaya) and flavonoids (19.47 ± 1.89 mg QE/g for Alstonia boonei and 18.24 ± 1.36 mg QE/g for Carica papaya). In vitro antioxidant activity measured as total antioxidant power, total reducing power, and DPPH radical scavenging activity showed that the extracts possessed higher antioxidant activity than the reference compounds. The outcome of the chemosuppressive test revealed that whereas Plasmodium berghei-infected mice had high parasitemia, decreased mean survival time, exhibited loss of weight, and had low PCV, treatment with the extracts reversed the effects in a concentration-dependent manner. Similarly, the curative test revealed that the extracts significantly suppressed parasitemia compared with the malaria negative control group. This was mirrored by reversal of indices of hepatic toxicity (AST, ALT, and ALP levels), nephropathy (urea and creatinine levels), oxidative stress (SOD, CAT, GPx, GSH, and lipid peroxides), and dyslipidemia (TC, HDL, and TG levels and HMG-CoA reductase activity) in infected but treated mice compared with negative control. Put together, the results of this study demonstrate that the extracts of Alstonia boonei and Carica papaya possess antimalarial properties and are able to ameliorate metabolic dysregulations that characterize Plasmodium berghei infection. The phytoconstituents in these extracts are believed to be responsible for the pharmacological activity reported in this study.
Highlights
Malaria still remains a threat to life especially in children below the age of 5 in sub-Saharan Africa
Medicinal plants have been used for decades in the treatment of diseases, and they continue to be a pool for the discovery of drug leads [2]. e present study reports the antimalarial activity of Alstonia boonei and Carica papaya in P. bergheiinfected mice. is study showed that the hydroethanolic extracts of Alstonia boonei and Carica papaya contain alkaloids, flavonoids, phenolics, tannins, saponins, anthraquinones, and terpenoids (Table 1)
Flavonoids, and tannins are known for their antioxidant, antimalarial, antimicrobial, anticancer, and anti-inflammatory activities [27, 28]. e extracts had total phenolics (34.13 ± 1.90 mg gallic acid equivalent (GAE)/g for Alstonia boonei and 27.99 ± 1.46 mg GAE/g for Carica papaya) and total flavonoid (19.47 ± 1.89 mg QE/g for Alstonia boonei and 18.24 ± 1.36 mg QE/g for Carica papaya)
Summary
Malaria still remains a threat to life especially in children below the age of 5 in sub-Saharan Africa. In Nigeria, folklore use of medicinal plants is a common practice due to accessibility, cultural acceptability, and relative affordability This is usually at the risk of safety as most of the traditional remedies are without scientifically proven efficacy. Extracts of Alstonia boonei have been reported to be rich in phytochemicals, which could target a plethora of plasmodium metabolic pathways One of such reports showed that a compound isolated from A. boonei inhibits the activity of both lactate dehydrogenase and plasmepsin II in malaria parasites [9]. Despite the above reports, there are no available data on the antiplasmodial effect of aqueous and ethanolic extracts of the leaf of these plants to justify their use in traditional medicine for the treatment of malaria. Compounds identified from the phytochemical screen can be investigated further for the discovery of potent drug leads against malaria
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