A search for natural bioactive compounds in Bolivia through a multidisciplinary approach Part IV. Is a new haem polymerisation inhibition test pertinent for the detection of antimalarial natural products?

The search for new antimalarial agents in plant crude extracts using tradit ional screening tests is time-consuming and expensive. New in vitro alterna tive techniques, based on specific metabolic or enzymatic process, have rec ently been developed to circumvent testing of antimalarial activity in para site culture. The haem polymerisation inhibition test (HPIA) was proposed a s a possible routine in vitro assay for the detection of antimalarial activ ity in natural products. A total of 178 plant extracts from the Pharmacopei a of the Bolivian ethnia Tacana, were screened for their ability to inhibit the polymerisation of haematin. Five extracts from Aloysia virgata (Ruiz & Pavon) A.L. Jussieu (Verbenaceae), Bixa orellana L. (Bixaceae), Caesalpini a pluviosa D.C. (Caesalpiniaceae), Mascagnia stannea (Griseb) Nied. (Malpig hiaceae) and Trichilia pleenea (Adr. Jussieu) (Meliaceae) demonstrated more than 70% inhibition of haematin polymerisation at 2.5 mg/ml. The extracts were also tested for antimalarial activity in culture against F32 Strain (c hloroquine-sensitive) and D2 strain (chloroquine-resistant) of Plasmodium? falciparum? and in vivo against P. berghei. The extract from Caesalpinia pl uviosa was the only one that showed activity in HPIA and in the classical t est in culture. The accuracy and pertinence of HPIA, applied to natural pro ducts is discussed. (C) 2000 Published by Elsevier Science Ireland Ltd.