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

Three known compounds, 20-deoxyphorbol-5β-hydroxy-12-tiglate-13-isobutyrate (1), 20-deoxyphorbol-5β-hydroxy-12-tiglate-13-phenylacetate (2), and 4-deoxy-4β-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.