Three new terpenoid metabolites (1-3) were isolated from the CH2Cl2 extract of the soft coral Lobophytum crassum together with the eudesmane derivative 4 and the known cembrane (2S,7S,8S)-sarcophytoxide (5). Compound 1 is a new cembrane-based diterpene with an C7-C8-epoxide and a methyl ester functionality at C-16. (3E,5Z)- (2) and (3Z,5E)-2-methyl-6-(4a'-methyl-8'-methylene-trans-perhydr onaphthalen-2'-yl)hepta-3,5-dien-2-ol (3) represent two new carbon-carbon double bond isomers of 4, which has the 3E,5E-configuration. The structures of 1-5 were established by interpretation of their spectroscopic data, mainly 1D and 2D NMR and MS. Biological activity evaluation of compounds 1 and 5 and the crude extracts was carried out using agar diffusion assays toward microbial targets and ELISA assays for investigating the inhibition of HIV-1 reverse transcriptase and p56lck tyrosine kinase.
Inhibitors of HIV reverse transcriptase (RT) are important drugs for the treatment of acquired immuno-deficiency syndrome (AIDS). One approach to identify novel inhibitors of HIV-1-RT is the screening of natural compounds. Many natural products have been shown to be active as RT inhibitors. These compounds belong to a wide range of different structural classes, e.g., coumarins, flavonoids, tannins, alkaloids, lignans, terpenes, naphtho-and anthraquinones, and polysaccharides. The life forms from which the bioactive compounds were isolated are as equally diverse and comprise terrestrial and marine plants, micro-organisms, and marine animals. From the most extensive screening effort, carried out by the NCl, calanolide A, isolated from the terrestrial plant Calophyllum lanigerum (Guttiferae), has been discovered as the most interesting natural RT inhibitor. The promise of this natural product probably relates to a novel mechanism of action. The current review describes natural products from various sources that are able to inhibit HIV-RT.
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