Oxazole-Containing Diterpenoids from Cell Cultures of Salvia miltiorrhiza and Their Anti-HIV‑1 Activities

Four new oxazole-containing diterpenoids, salvianans A–D (1–4), along with three known diterpenoids (5–7), were isolated from Salvia miltiorrhiza cell cultures. The structures of the new compounds were elucidated using spectroscopic methods and single-crystal X-ray diffraction. The evaluation for their anti-HIV-1 activities revealed that 2 and 3 displayed inhibitory activities with IC50 values of 0.03 and 1.2 μM, respectively. The time of addition (TOA) assay and long terminal repeat (LTR) luciferase reporter assay results indicated that compound 2 was an HIV-1 transcription inhibitor and might be a lead compound of antiviral agents acting on HIV-1 transcription.