Monoamine oxidase inhibitors from rhizoma of Coptis chinensis

Three protoberberine alkaloids jatrorrhizine, berberine and palmatine were isolated from the monoamine oxidase (MAO) inhibitory fraction of the methanol extract of Coptis chinensis rhizoma. Jatrorrhizine was shown to inhibit non-competitively both MAO-A and -B from rat brain mitochondria with the IC50 values of 4 and 62 muM, respectively. Berberine only competitively inhibited MAO-A with an IC50 values of 126 muM whereas palmatine exhibited, up to 200 muM, no inhibition on any type of the enzyme. The structure-activity relationship was briefly discussed.