RESUMEN
We have synthesized new derivatives of the macrolide antibiotics erythromycin and azithromycin. Novel deoxysugar moieties were attached to these standard antibiotics by biotransformation using a heterologous host. The resulting compounds were tested against several standard laboratory and clinically isolated bacterial strains. In addition, they were also tested in vitro against standard and drug-resistant strains of human malaria parasites (Plasmodium falciparum) and the liver stages of the rodent malaria parasite (Plasmodium berghei). Antibacterial activity of modified erythromycin and azithromycin showed no improvement over the unmodified macrolides, but the modified compounds showed a 10-fold increase in effectiveness after a short-term exposure against blood stages of malaria. The new compounds also remained active against azithromycin-resistant strains of P. falciparum and inhibited growth of liver-stage parasites at concentrations similar to those used for primaquine. Our findings show that malaria parasites have two distinct responses to macrolide antibiotics, one reflecting the prokaryotic origin of the apicoplast and a second, as-yet uncharacterized response that we attribute to the eukaryotic nature of the parasite. This is the first report for macrolides that target two different functions in the Plasmodium parasites.
Asunto(s)
Antimaláricos/síntesis química , Antimaláricos/farmacología , Plasmodium berghei/efectos de los fármacos , Plasmodium falciparum/efectos de los fármacos , Azitromicina/análogos & derivados , Azitromicina/farmacología , Cloroquina/farmacología , Resistencia a Medicamentos , Eritromicina/análogos & derivados , Eritromicina/farmacología , Macrólidos/síntesis química , Macrólidos/farmacología , Malaria/tratamiento farmacológico , Malaria/parasitología , Pruebas de Sensibilidad Parasitaria , Plasmodium berghei/crecimiento & desarrollo , Plasmodium falciparum/crecimiento & desarrolloRESUMEN
In vivo reconstitution of the TDP-l-megosamine pathway from the megalomicin gene cluster of Micromonospora megalomicea was accomplished by the heterologous expression of its biosynthetic genes in Escherichia coli. Mass spectrometric analysis of the TDP-sugar intermediates produced from operons containing different sets of genes showed that the production of TDP-l-megosamine from TDP-4-keto-6-deoxy-d-glucose requires only five biosynthetic steps, catalyzed by MegBVI, MegDII, MegDIII, MegDIV, and MegDV. Bioconversion studies demonstrated that the sugar transferase MegDI, along with the helper protein MegDVI, catalyzes the transfer of l-megosamine to either erythromycin C or erythromycin D, suggesting two possible routes for the production of megalomicin A. Analysis in vivo of the hydroxylation step by MegK indicated that erythromycin C is the intermediate of megalomicin A biosynthesis.
Asunto(s)
Aminoglicósidos/biosíntesis , Vías Biosintéticas/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Micromonospora/genética , Familia de Multigenes , Aminoglicósidos/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Eritromicina/metabolismo , Orden Génico , Glucosa/análogos & derivados , Glucosa/metabolismo , Modelos Biológicos , Estructura Molecular , Operón , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Nucleótidos de Timina/metabolismoRESUMEN
Six 3H-spiro[benzofuran-2,1'-cyclohexane] derivatives were synthesized from naturally occurring filifolinol, and their classical complement pathway inhibitory activity was determined. IC(50) values of the most potent compounds were comparable to the activity of the natural complement inhibitor K76-COOH and some synthetic tricyclic analogs of it.