Acacetin is an O-methylated flavone found in Robinia pseudoacacia (black locust), Turnera diffusa (damiana), Betula pendula (silver birch), and in the fern Asplenium normale. Acacetin is an O-methylated flavone found in Robinia pseudoacacia (black locust), Turnera diffusa (damiana), Betula pendula (silver birch), and in the fern Asplenium normale. The enzyme apigenin 4'-O-methyltransferase uses S-adenosyl methionine and 5,7,4'-trihydroxyflavone (apigenin) to produce S-adenosylhomocysteine and 4'-methoxy-5,7-dihydroxyflavone (acacetin).