Screening of selected Nigerian ethnomedicines for inhibition of β- haematin formation

Malaria chemotherapy as recommended by the World Health Organisation (WHO) is based on combination of drugs such as the Artemisinin-based Combination Therapy (ACT) (WHO, 2008). This regimen though widely used and effective has drawback of incompatibility in pharmacokinetics (Fidock et al, 2004), pre-existent parasite resistance and high cost (Onwujekwe, 2004). This makes the discovery of new compounds (Kurosawa et al, 2000) that inhibit formation of β- haematin, the most frequently used drugs in combination with the artemisinins, important.

Selected components (25) of recipes used traditionally to treat malaria in South-western Nigeria have been screened for inhibition of β-haematin formation after the modified methods of Ncokazi and Egan (2005) and Vargas et al (2011). Active methanol extracts were identified and selected by visual examination (net formation of bright pink colouration) and absorbance measurement on a SoftMax Pro 5.4 plate reader. Most active extracts identified were Newbouldia laevis Seem leaf, (Inhibitory value, I _value 0.88 ± 0.39), Rhaphiostylis beninensis, (Hook. f.) Planch leaf (I_value 0.23 ± 0.15). (Chloroquine phosphate, I_value 0.72 ± 0.19. The I _value measures the inhibition of β-haematin formation; positive values are selected and highest magnitude equals the absorbance of the initial concentration of haematin used in assay). The bioactivity guided fractionation and isolation of selected active extracts using standard chromatographic methods is on-going and will be presented.

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