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Many of the African antimalarial ethno medicinal plants are good sources of promising antimalarial compounds. The stem bark of Plumeria alba Linn, was evaluated for in vivo chemosuppressive antimalarial activities in order to identify the most active solvent  fraction from which antimalarial constituents can be isolated. The stem-bark of Plumeria alba Linn, family Apocynaceae was   collected, air-dried, powdered, macerated in methanol and the extract concentrated in vacuo. The acute toxicity study was   performed on the extract using Lorke’s method. The extract was thereafter tested for chemosuppressive antiplasmodial activities against Plasmodium berghei berghei NK65- infected mice using Peter’s four-day test at doses 100-800 mg /kg with normal saline (0.2 ml) and chloroquine (10 mg/kg) as negative and positive control drugs respectively. The average percentage parasitaemia, percentage chemosuppression and effective doses (ED50 and ED90), the survival times and percentage survivors elicited in all the  mice were  determined as indices of antimalarial activity. The active extract was  subsequently partitioned successively into n-hexane, dichloromethane, ethyl acetate and butanol. The respective partitioned fractions with the aqueous phase were also tested as above at doses 0-80 mg/kg. All results were  subjected to statistical analysis using ANOVA with Student Newman Keul’s post hoc test. Crude extracts of P. alba gave considerable reduction of percentage parasitaemia up to 200 mg/kg. The percentage  chemosuppression at all doses, were significantly higher (p<0.05) than the negative but lower than the positive control with 200 mg/kg dose showing the highest activity of 65.88 %. The effective doses, ED50 and ED90 were  305.82±9.99 and 389.74± 9.60, respectively. The most active n-hexane partitioned fraction elicited a percentage chemosuppression of 67.75 and a significantly lower (p<0.05) ED50 and ED90 of 31.27±0.85 and 54.80±1.75 mg/kg. The butanol and ethyl acetate partitioned fractions gave significantly higher (p<0.05) survival time value than those of the crude extract, other partition fractions and the positive control, while the n-hexane, dichloromethane and the aqueous, just like chloroquine, gave high percentage survivors. The study concluded that Plumeria alba stem-bark extract was active as an antimalarial drug with its antiplasmodial and the survival time–enhancing activity concentrated in the n-hexane and ethyl acetate with butanol partitioned fractions respectively, thus confirming and justifying its ethnomedical application in malaria.

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Malaria is a deadly disease that continues to pose a threat to children and maternal well-being. This study was designed to identify the chemical constituents in the ethanolic fruit extract of Azadirachta indica, elucidate the pharmacological potentials of identified phytochemicals through the density functional theory method and carry out the antimalarial activity of extract using chemosuppression and curative models. The liquid chromatography-mass spectrometry (LC-MS) analysis of the ethanolic extract was carried out, followed by the density functional theory studies of the identified phytochemicals using B3LYP and 6-31G (d, p) basis set. The antimalarial assays were performed using the chemosuppression (4 days) and curative models. The LC-MS fingerprint of the extract led to the identification of desacetylnimbinolide, nimbidiol, O-methylazadironolide, nimbidic acid, and desfurano-6α-hydroxyazadiradione. Also, the frontier molecular orbital properties, molecular electrostatic potential, and dipole moment studies revealed the identified phytochemicals as possible antimalarial agents. The ethanolic extract of A indica fruit gave 83% suppression at 800 mg/kg, while 84% parasitaemia clearance was obtained in the curative study. The study provided information about the phytochemicals and background pharmacological evidences of the antimalarial ethnomedicinal claim of A indica fruit. Thus, isolation and structure elucidation of the identified phytochemicals from the active ethanolic extract and extensive antimalarial studies towards the discovery of new therapeutic agents is recommended for further studies.

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