HIV reverse transcriptase inhibitors of natural origin

Inhibitors of HIV reverse transcriptase (RT) are important drugs for the tr eatment of acquired immune-deficiency syndrome (AIDS). One approach to iden tify novel inhibitors of HIV-1-RT is the screening of natural compounds. Ma ny natural products have been shown to be active as RT inhibitors. These co mpounds belong to a wide range of different structural classes, e.g., couma rins, flavonoids, tannins, alkaloids, lignans, terpenes, naphtho- and anthr aquinones, and polysaccharides. The life forms from which the bioactive com pounds were isolated are as equally diverse and comprise terrestrial and ma rine plants, micro-organisms, and marine animals. From the most extensive s creening effort, carried out by the NCI, calanolide A, isolated from the te rrestrial plant Calophyllum lanigerum (Guttiferae), has been discovered as the most interesting natural RT inhibitor. The promise of this natural prod uct probably relates to a novel mechanism of action. The current review des cribes natural products from Various sources that are able to inhibit HIV-R T.