Berberine is an alkaloid found in various different medicinal herbs mainly extracts from Berberis amurensis. Yes it crosses blood brain barrier. Its plasma levels occurs in a range of 1.8 μg/ml (∼ 5 μM) berberine . An amount of 350 ng/g (∼ 1 μM) berberine occurs in the hippocampus showing that berberine can cross the blood-brain barrier. CSF also contain 150-400 ng/g concentration.