A panel of nine dibenzo[a,c]cyclooctadiene lignans, schizandrin, gomisin A, gomisin N, gomisin J, angeloylgomisin H, tigloylgomisin P, deoxyschizandrin, gamma-schizandrin and wuweizisu C was examined for their effect on multidrug resistance, as well as their anti-proliferative activities. COR-L23/R,