Flavonoid 3'-hydroxylase that catalyzes the 3'-hydroxylation of flavanones, dihydroflavonols and flavonols (PubMed:31004005). Converts narigenin to eriodictyol, dihydrokaempferol to dihydroquercetin and kaempferol to quercetin (PubMed:31004005). a 3'-unsubstituted flavone + O2 + reduced [NADPH--hemoprotein reductase] = a 3'-hydroxyflavone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] (2S)-naringenin + O2 + reduced [NADPH--hemoprotein reductase] = (S)-eriodictyol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] (2R,3R)-dihydrokaempferol + O2 + reduced [NADPH--hemoprotein reductase] = (2R,3R)-dihydroquercetin + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] kaempferol + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + H2O + oxidized [NADPH--hemoprotein reductase] + quercetin Flavonoid metabolism. Expressed in young cromes. Belongs to the cytochrome P450 family.