Chemotherapeutic activity of Azadirachta indica leaf extract and its cyclodextrin complex on Plasmodium berghei infected mice

Abstract

This study investigated the antimalarial activity of Azadirachta indica leaf extract complexed with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) alone and a combination of HP-β-CD and polyvinylpyrrolidone (PVP) with a view to improving the antimalarial activity of the complex. Hot aqueous extract (HAE), hot hydroalcoholic extract (HEE) and cold hydroalcoholic extract (CEE) of A. indica were assessed for suppressive and curative in vivo antimalarial activity following established procedures. HAE was selected for complexation because aqueous extraction is the most commonly used preparation in ethnomedicine; CEE and HEE did not show superior efficacy in the antimalarial tests. HAE-HP-β-CD complexes (at each of 50, 100, 200 and 400 mg/kg) were prepared by freeze-drying at a weight ratio 1:1. HAE (400 mg/kg) - HP-β-CD-PVP complexes were also prepared with each of 5%, 10%, and 20% w/w PVP. The complexes were subjected to curative tests and data were analyzed. In the suppressive tests, CEE, HAE and HEE produced chemosuppression of 75.0%, 78.2% and 77.7% at 400 mg/kg, respectively. HAE at 400 mg/kg produced the lowest percentage parasitemia on day 5 in the curative tests. In the curative test, HAE (400 mg/kg) - HP-β-CD complex showed superior efficacy, (F_{[5, 22]} = 5.06, P < 0.05), when compared to complexes of lower doses. HAE (400 mg/kg) alone attained 57.9% chemosuppression on day 6 while HAE (400 mg/kg) – HP-β-CD complex attained 51.5%. HAE-HP-β-CDPVP complexes gave about 30% chemosuppression. The study concluded that complexation of an aqueous extract of Azadirachta indica leaf with HP-β-CD at 400 mg/kg produced significant improvement in the activity of the extract while HP-β-CD and PVP complexes did not significantly improve the curative activity.