Rapid screening of brain-penetrable antioxidants from natural products by blood-brain barrier specific permeability assay combined with DPPH recognition

Screening brain-penetrable antioxidants from natural products is a promising way for neuroprotective drug discovery. However, there is no screening methodology enables simultaneous investigation of antioxidant activity and blood-brain barrier (BBB) permeability of compounds from complex samples. Here we propose a novel strategy by combining BBB specific parallel artificial membrane permeability assay with 1,1-diphenyl-2-picrylhydrazyl recognition (BBB-PAMPA-DPPH) to achieve rapid multicomponent screening. First, BBB specific artificial membrane was constructed to separate the compounds with high BBB permeability in herbal extracts. The antioxidant activity of the isolated compounds could be optically recognized through the bleaching of the purple-colored DPPH. By off-line combined HPLC-UV/Q-TOF-MS analysis, the exact BBB-penetrable compounds responsible for the antioxidant activity could be rapidly screened. With this approach, compound 2,6,4′-trihydroxy-4-methoxybenzophenon in Rhizoma Anemarrhena was found to be an antioxidant with very high BBB permeability, which could also be detected in rat plasma and brain tissue after oral administration. Our findings suggested the BBB-PAMPA-DPPH method could be a powerful tool for neuroprotective drug discovery from natural products.