Camellimidazole A-C, Three Methylene-Bridged Dimeric Imidazole Alkaloids from Keemun Black Tea.

Three new dimeric imidazole alkaloids with a methylene bridge, camellimidazole A-C (1-3), were isolated from Keemum black tea. Their structures were completely elucidated by a combination of diverse spectroscopic and single-crystal X-ray diffraction analyses. The plausible formation pathway of camellimidazole A-C was proposed. Compounds 1 and 2 exhibited remarkable protection against H2O2-induced neuronal damage at the concentration of 1.0 μM.