Direct characterization of isoquinoline alkaloids in a crude plant extract by ion-pair liquid chromatography-electrospray ionization tandem mass spectrometry: example of Eschscholtzia californica.

An ion-pair HPLC-ESI-MS-MS method has been developed for the direct and rapid characterization of isoquinoline alkaloids in a crudely purified extract of the aerial parts of Eschscholtzia californica (Papaveraceae). This plant was chosen because of its increasing use in pharmaceutical industries and because its well known alkaloid composition allows the optimization of the experimental procedure through an on-line analytical sequence. Thus, 14 isoquinoline alkaloids of different types were detected and characterized. The identities of these compounds were confirmed unambigously by their fragmentation and UV spectra obtained by LC-diode-array detection. Various experiments including tandem mass spectrometry and in-orifice collision induced dissociation were performed and prove that MS-MS is a very efficient technique to identify these compounds. An explanation for each isoquinoline alkaloid type MS-MS fragmentation pattern is proposed and indicates similar neutral and/or radical losses. The order of the fragmentation depended on the type of compound but the lost fragments were similar.

Basic biochemical investigations as rationale for the design of original antimalarial drugs. An example of phospholipid metabolism.

The future of antimalarial chemotherapy is particularly alarming in view of the spread of parasite cross-resistances to drugs that are not even structurally related. Only the availability of new pharmacological models will make it possible to select molecules with novel mechanisms of action, thus delaying resistance and allowing the development of new chemotherapeutic strategies. We reached this objective in mice. Our approach is hunged on fundamental and applied research begun in 1980 to investigate the phospholipid (PL) metabolism of intraerythrocytic Plasmodium. This metabolism is abundant, specific and indispensable for the production of Plasmodium membranes. Any drug able to interfere with this Plasmodium membranes. Any drug able to interfere with this metabolism blocks parasitic development. The most effective interference yet found involves blockage of the choline transporter, which supplies Plasmodium with choline for the synthesis of phosphatidylcholine, its major PL, this is a limiting step in the pathway. The drug sensitivity threshold is much lower for the parasite, which is more dependent on this metabolism than host cells. The compounds show in vitro activity against P. falciparum at 1 to 10 nM. They show a very low toxicity against a lymphoblastoid cell line, demonstrating a total absence of correlation between growth inhibition of parasites and lymphoblastoid cells. They show antimalarial activity in vivo, in the P. berghei or P. chabaudi/mouse system, at doses 20- to 100-fold lower than their acute toxicity limit. The bioavailability of a radiolabeled form of the product seemed to be advantageous (slow blood clearance and no significant concentration in tissues). Lastly, the compounds are inexpensive to produce. They are stable and water-soluble.