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Biomedical subjects

J D Phillipson

Publications and source records attributed to J D Phillipson.

At least 55 records · Page 3Linked to original sources
PubMed1989

In vitro studies on the mode of action of quassinoids with activity against chloroquine-resistant Plasmodium falciparum.

Using the incorporation of [3H]isoleucine or [3H]hypoxanthine into acid-insoluble products as indices of protein- and nucleic acid-synthetic activity, respectively, it was shown that seven plant-derived quassinoids with differing chemical substitutions all inhibited protein synthesis more rapidly than nucleic acid synthesis in human erythrocytes infected with Plasmodium falciparum, in vitro. Five quassinoids (ailanthinone, bruceantin, bruceine B, glaucarubinone and holacanthone) were effective within 30 min at doses 10 times their 48 hr in vitro IC50 values. Chaparrin and glaucarubol differed in that they did not inhibit protein synthesis during the time course of these experiments when applied at 10 times their in vitro IC50 values. When these compounds were used at 209 and 114 times their respective IC50 values, their observed effects were identical to those of the other quassinoids studied. The time (t50) at which nucleic acid synthesis was reduced to 50% of control was directly proportional to the t50 for protein synthesis, suggesting that failure of nucleic acid synthesis is a consequence of inhibition of protein synthesis. It is concluded that in the malaria parasite, as in eukaryote models, quassinoids are rapid and potent inhibitors of protein synthesis, and that this is most likely due to effects upon the ribosome, rather than upon nucleic acid metabolism.

Animals↗
PubMed1989

Ethnopharmacology and Western medicine.

The contribution of plants to western medicine is briefly considered using alkaloids as examples of one class of pharmacologically active natural product. Plants and plant products are present in 14 of the 15 therapeutic categories of pharmaceutical preparations which are currently recommended to medical practitioners in the U.K. and they form an important part of our health-care system in the western world. There is considerable scope for new drug discovery from traditional medicines which are used throughout the world and some recent developments are commented upon and conclusions are made.

Ethnology↗
PubMed1988

Use of microdilution to assess in vitro antiamoebic activities of Brucea javanica fruits, Simarouba amara stem, and a number of quassinoids.

A microdilution technique for the assessment of in vitro activity against Entamoeba histolytica was devised and validated with metronidazole. The test was used to detect the antiamoebic activities of plant extracts prepared from the traditional remedies Brucea javanica fruits and Simarouba amara stems. The activity was associated with quassinoid-containing fractions. The 50% inhibitory concentrations for some quassinoids against amoebae were determined by using the microdilution method. These concentrations ranged from 0.019 micrograms.ml-1 for bruceantin, the most active quassinoid, to greater than 5 micrograms.ml-1 for glaucarubol, the least active compound tested. These results are discussed with reference to the known activities of these compounds against Plasmodium falciparum. Overall, the activities of the quassinoids against both protozoa are similar. The microdilution technique will be useful in the search for novel antiamoebic drugs.

Amebicides↗
PubMed1987

Potentiation of the antimalarial activity of qinghaosu by methoxylated flavones.

Interaction between the flavones casticin and artemetin and the antimalarial activity of chloroquine and qinghaosu (QHS) was examined using an in vitro growth assay based on [3H]hypoxanthine incorporation in synchronized cultures of a cloned line of Plasmodium falciparum. Casticin, and to a lesser extent artemetin, selectively enhanced the inhibition of growth by QHS, but had little effect on the activity of chloroquine. The findings suggest that flavones indigenous to Artemisia annua, from which QHS is isolated, might significantly alter the clinical potential of this novel antimalarial drug in the treatment of chloroquine-resistant malaria.

Animals↗
PubMed1986

Novel antimalarial drugs from plants?

In all countries where malaria is endemic, plants are used in traditional medicine for treatment of the disease. Examples are numerous - the plant product data base napralert (Box I) lists 152 genera which are allegedly used for the treatment of malaria. But with the urgent need to develop new, safe and effective drugs against malaria, it is vital that such claims be fully investigated. In this article, David Phillipson and Melanie O'Neill discuss the potential of plant products for new antimoloriols, drawing attention particularly to the quassinoids - a diverse group of terpenoids from the family Simoroubaceoe.

Journal Article↗
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↗