Investigation on the antimalarial properties of Plumeria alba Linn (apocynaceae) cultivated in Nigeria

Abstract

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.