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