Phorbol Esters from the Latex of Euphorbia umbellata: Bioguided Isolation of Highly Potent HIV-1 Latency Interrupters in Virus Reservoir Cells.

ABSTRACT

Three known compounds, 20-deoxyphorbol-5ß-hydroxy-12-tiglate-13-isobutyrate (1), 20-deoxyphorbol-5ß-hydroxy-12-tiglate-13-phenylacetate (2), and 4-deoxy-4ß-phorbol-12-tiglate-13-phenylacetate (3), were reisolated from the latex of Euphorbia umbellata through a bioguided fractionation process to target HIV-1 latency reactivation. The in vitro bioassay using infected T-cell lymphoblasts (J-Lat 10.6), complemented with surface CD4 receptor downregulation assessment, led to isolation of the compounds as a highly active ternary mixture. Effective purification of the individual compounds was achieved by first subjecting a phorbol-enriched fraction (previously prepared from crude latex) to MPLC, followed by semipreparative HPLC and characterization by 1D and 2D NMR spectroscopy and (+)-HRESIMS. Compared with a positive control, the isolated compounds were effective in reactivating 68-75% of the virus latency in the range of 9.7-0.097 µM for compound 1, 8.85-0.088 µM for compound 2, and 9.1-0.091 µM for compound 3, with the latter maintaining steady effectiveness down to a 10-5 dilution. Accordingly, compound 3 may serve as a promising lead compound for the development of anti-HIV drugs based on latency reactivation therapy.