Antimalarial activity assay

In vivo assays were performed using the standard Peters 4-day test. Ihe activity refers to oral antimalarial activity and reflects the concentration of drug required to reduce parasitaemia, in mice infected with Plasmodium berghei, by 50% of the control. 

An additional step in the radical mechanism has been suggested namely, that collapse of C-4 radical intermediate 234 to a neutral but highly reactive alkoxy-epoxide 235 occurs (Scheme 5).104 Protein alkylation then presumably occurs via 235 and not radical intermediates such as 234. Unfortunately, epoxide 235 is probably too unstable to be handled or identified. In the case of 258 however, we were granted the opportunity to test the hypothesis that an intermediate epoxide was responsible for the mode of action. Of the series of three tetracycles, 258 retained nearly two-thirds of the activity of artemisinin. The Fe(II)-induced rearrangement product 281, a quite stable epoxide was submitted for antimalarial assay and found to be completely devoid of activity. As 258 is a potent antimalarial but the epoxide 281 is not, it seems reasonable to suggest that the antimalarial activity of 258 is unrelated to epoxy intermediates. 

A rapid semiautomated microdilution method for the microbiological assay of the chloroquine has been developed by Desgardins (26). Antimalarial activity of chloroquine may be studied against cultured Plasmodium falciparum, microplates are used to prepare serial dilution of the drug. Parasites obtained from continuous stock cultures are subcultured in the micro-plates for 42 h. Inhibition of uptake of a radio labeled nucleic acid precursor by parasites serves as the indicator of antimicrobial activity. 

Antimalarial ADME/tox assays in vitro in vivo testing, hit L identification A r Virtual screening- Predict antimalarial actives, ADME/tox t properties A... 

Primary assay. The primary assay is comprehensive with regard to its capacity to detect potential antimalarial activity, since there is no intent to exclude any antiplasmodial compounds at this stage, regardless of mechanism of action. This bioassay relies upon in vitro methodology for the culture of P. falciparum within human erythrocytes (110) and is widely used for investigation of potential antimalarial compounds. The method evaluates the ability of test substances to inhibit parasite proliferation by measuring the incorporation of a radiolabeled purine into plasmodial DNA (111). 

Compared with the plethoric studies on antiplasmodial activity against P. falciparum in vitro, in vivo antimalarial assays dedicated to quassinoids are scarce and hardly comparable. Nevertheless, the excellent antimalarial activities highlighted in those studies should open the way to complementary studies of their pharmacokinetics and toxicity. Association with other antimalarials should also be investigated in order to define new therapeutic schemes and to lower the administered doses, increasing drugs tolerability. 

In Vivo, In Vitro and Chemical Assays for the Detection of Antimalarial and Heme Aggregation Activity. 

Ribosomes of Plasmodium knowlesi were isolated and characterized recently by Sherman et al. 21 These ribosomes sedimented in the 80S range and could be dissociated into 60S and 40S subparticles. The ribosomal RNA had a low % G+C of 37% and had sizes of 24.2S and 16.6S.22 The ribosomes demonstrated high activity in poly(IJ)-directed synthesis of polyphenylalanine and were strongly inhibited by 10 4m of nucleocidin, chlortetracycline, ethidium, puromycin, cycloheximide or berenil.23 Similar studies have been also carried out on Plasmodium lophurae, and similar profile of drug sensitivities were demonstrated.24 Most of the well-known antimalarial drugs tested showed no significant inhibitory activity in this in vitro assay. 

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