New Anti-HIV Agents Isolated From Two Euphorbia Species

Four previously unreported tigliane diterpenes (1, 2, 4, and 6), along with two known tiglianes (3 and 5), were isolated from the latex of Euphorbia palustris and Euphorbia lucida. The structures of the isolated compounds were elucidated by spectroscopic techniques. Antiviral activity assays for compounds 1‒4 and 6 against HIV-1 and HIV-2 replication were performed on a CD4⁺ T cell line, MT-4 cells. The compounds were tested for their ability to inhibit infection by the HIV-1 strain NL4.3 and the HIV-2 strain ROD. Compound 6 showed no activity against either strain, while compound 4 was only slightly active against HIV-2 (EC₅₀ = 12.778 µM). Compounds 1, 2, and 3 were able to inhibit both HIV-1 and HIV-2 infections. Among them, compound 2 was the most potent, with EC₅₀ values of 0.069 µM for HIV-1 NL4.3 and 0.023 µM for HIV-2 ROD. The PBMC toxicity profile for compound 2 is also more favorable compared with MT-4 cells with CC₅₀ = 50 μM.