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PubMed2005

Synthesis of some cryptolepine analogues, assessment of their antimalarial and cytotoxic activities, and consideration of their antimalarial mode of action.

A series of analogues of cryptolepine (1) have been synthesized and evaluated for their in vitro antiplasmodial and cytotoxic properties. The IC(50) values of several compounds (11a, 11k-m, 11o, 13) against Plasmodium falciparum (strain K1) were <0.1 muM, 5-10-fold lower than that of 1 but their cytotoxicities were only 2-4 times greater than that of 1. Compounds with a halogen in the quinoline ring and a halogen or a nitro group in the indole ring have enhanced antiplasmodial activity. In mice infected with P. berghei, the 7-bromo-2-chloro (11k) and 2-bromo-7-nitro (13) derivatives of 1 suppressed parasitemia by >90% at doses of 25 mg kg(-1) day(-1) with no apparent toxicity to the mice. 2,7-Dibromocryptolepine (15) was evaluated at several dose levels, and a dose-dependent suppression of parasitemia was seen (ED(90) = 21.6 mg kg(-1) day(-1)). The antimalarial mode of action of 1 appears to be similar to that of chloroquine and involves the inhibition of hemozoin formation. A number of analogues were assessed for their effects on the inhibition of beta-hematin (hemozoin) formation, and the results were compared with their antiplasmodial activities having taken account of their predicted accumulation into the acidic parasite food vacuole. No correlation was seen (r(2) = 0.0781) suggesting that the potent antimalarial activity of compounds such as 15 involves other mechanisms in addition to the inhibition of hemozoin formation.

Algorithms↗
PubMed1996

Antimalarial activity: the search for marine-derived natural products with selective antimalarial activity.

In this short review, an approach to the isolation of potential antimalarial agents and lead compounds is outlined. A discussion of organism collection, followed by a description of biological testing and isolation methodologies, is also given. For two organisms, details of their secondary metabolite chemistry are reported. From one of these, Laurencia papillosa, the two aromatic compounds p-hydroxybenzaldehyde (1) and p-methoxybenzyl alcohol (2) were isolated. From the other, the tropical marine sponge Cymbastela hooperi, 15 diterpenes (3-17), which contain isonitrile, isothiocyanate, and isocyanate functionalities, are reported. Together with the diterpenes, three sesquiterpene hydrocarbons, 18-20, and the thiol, 21, were obtained. All structures were established by spectroscopic methods, particularly 1H-1H and 1H-13C shift-correlated 2D NMR spectroscopy and accurate mass measurement (HREIMS). The majority of isolates demonstrate significant and selective in vitro antimalarial activity. For compounds 4-17 a brief description of their possible structure-activity relationships is provided.

Animals↗
PubMed2005

Traditional antimalarials and the development of novel antimalarial drugs.

Malaria continues to be a major cause of mortality and morbidity especially throughout the developing world. In the last 25 years or so a number of significant advances have been made that have the potential to make a major contribution to the control of this disease. The discovery of artemisinin and its analogues as potent antimalarial agents have been of immense importance and the latter, as well as some other selected developments are outlined in this brief review.

Antimalarials↗
PubMed1979

Antimalarials. 11. Synthesis of 3- and 5-aminoquinolines as potential antimalarials.

A series of 3-quinolinediamines (1g, 2c, and 3e) structurally related to primaquine and 4-methylprimaquine have been prepared and tested for antimalarial activity against Plasmodium berghei in mice and antileishmanial activity against Leishmania donovani in the hamster. All were inactive. In addition, three 5-quinolinediamines (4b, 5, and 6) were prepared. All were inactive against Leishmania donovani in hamsters. One of the examples, 6, was curative against Plasmodium cynmolgi in the rhesus monkey.

Aminoquinolines↗
PubMed1977

Antimalarials. 10. Synthesis of 4-substituted primaquine analogues as candidate antimalarials.

Primaquine (I) has been extensively used in combination with other drugs in the radical cure of relapsing malaria as well as for prophylaxis or the interruption of transmission. This, coupled with the activity data reported for 4-methylprimaquine (II), has led to the synthesis of a series of 14 4-substituted analogues of I. In addition, three side-chain analogues of II were prepared. The compounds were tested for suppressive antimalarial activity against Plasmodium berghei in the Rane mouse screen and for radical curative activity against Plasmodium cynomolgi in the rhesus monkey. Four of the 17 compounds prepared (1a, 9c, 15, and 17) exhibited activity in at least one of the test systems.

Animals↗
PubMed1976

Antimalarials. 8. Synthesis of amino ethers as candidate antimalarials.

Based upon the antimalarial activities demonstrated by compounds I and II a series of amino ethers represented by structures III-VI was synthesized. These structures incorporated several modifications of compound II. The compounds prepared displayed no activity in either the Rane P. berghei mouse screen or the Rane P. gallinaceum sporozoite-induced chick test.

Amines↗
PubMed1986

Plants as sources of antimalarial drugs: in vitro antimalarial activities of some quassinoids.

Fourteen quassinoids, obtained from simaroubaceous plants, were tested for in vitro antimalarial activity. All of these inhibited the incorporation of [3H]hypoxanthine into Plasmodium falciparum in vitro at concentrations below 0.41 microgram ml-1. The two most potent quassinoids, bruceantin and simalikalactone D, showed 50% inhibitory concentration values of 0.0008 and 0.0009 microgram ml-1, respectively. The results are compared with the antiamoebic, antileukemic, and cytotoxic activities of these compounds reported in the literature.

Amebicides↗
PubMed1975

Antimalarials. Synthesis and antimalarial activity of 1-(4-methoxycinnamoyl)-4-(5-phenyl-4-oxo-2-oxazolin-2-yl)piperazine and derivatives.

The preparation and activity against Plasmodium berghei of derivatives of 1-(4-methoxycinnamoyl)-4-(5-phenyl-4-oxo-2-oxazolin-2-yl)piperazine are described. Replacement of the cinnamoyl group was accomplished by acylation or alkylation of 1-(5-phenyl-4-oxo-2-oxazolin-2-yl)piperazine. Modifications of the 5-phenyl group were prepared either by a sequence of reactions involving mandelic ester-pemoline-piperazine pemoline or by the reaction of 5-aryl-2-thio-2,4-oxazolidinedione with piperazine or N-substituted piperazines. In a similar manner, pemoline was allowed to react with N-arylpiperazine, hexahydro-1H-1,4-diazepine, and 2,6-dimethylpiperazine to provide N-arylpiperazine pemoline derivatives and variations in the piperazine moiety. Several compounds in which the 2-oxazolin-4-one ring was replaced with other heterocyclic rings were prepared as were several open-chain analogs. Five compounds (three of them substituted in the para position of the 5-phenyl group and two N-arylpiperazine pemoline derivatives) were found to be active against Plasmodium berghei. The remaining active compound possessed changes in the cinnamoyl group and substitution on the 5-phenyl group.

Animals↗