Evaluation of Antimalarial Potential of Extracts from Alstonia boonei and Carica papaya in Plasmodium berghei-Infected Mice

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.

In vitro and in vivo antimalarial activity and chemical profiling of sugarcane leaves

“…Each mouse used in the experiment was inoculated intraperitoneally with 0.2 mL of infected blood containing about 1 × 10 7 P. berghei parasitized erythrocytes collected from an infected mouse with 20–30% parasitaemia. The inoculum consisted of 5 × 10 7 P. berghei infected erythrocytes per milliliter prepared by determining both the percentage parasitemia and the erythrocyte count of the donor mouse and diluting the blood with isotonic saline in proportions indicated by both determinations 8 , 26 , 27 . Parasitemia was monitored by standard methods; thin blood smears were made on glass slides, fixed using methanol, and stained using 10% Giemsa stain.…”

“…The suppressive activities of the leaf extract, fractions and chloroquine against P. berghei infection in mice were tested using methods previously described 26 , 27 , 29 . The study involved fifty-four mice which were inoculated with the parasite on the first day (D 0 ) and thereafter divided into nine groups each consisting of six mice.…”

“…The mean survival time (MST) of the mice in each treatment group was measured as reported previously 26 , 27 .…”

“…The mice were treated with the extract and fractions for three consecutive days (D 0 –D 2 ), while thin films were prepared from blood collected from the tail of each mouse on the fourth day (D 3 ) of the study to assess the parasitaemia level of the mice in each group. The animals were observed for a period of 29 days and mortality in each group was recorded with the date which was used to calculate the MST of the animal 26 .…”

“…Rectal temperature of individual mouse was monitored and recorded daily throughout the treatment period 32 . The animals were observed for a period of 29 days (D 0 –D 28 ) and mortality in each group was recorded with the date which was used to calculate the mean survival time of the animal 8 , 26 , 27 .…”