In search of blue-light photoreceptors for light-induced leaf opening we isolated from the aqueous extract of Albizia julibrissin Durazz. two flavins by adsorption on XAD-4 and separation with HPLC. One sample was identified as riboflavin la. In the hydrolysate of the second flavin fraction we found another dimethylisoalloxazine with a C5-side chain. Furthermore we isolated the cinnamoyl derivatives 3-0- (4-hydroxy-trans-cinnamoyl) quinic acid 2 and 3- 0-(3,4-dihydroxy-trans-cinnamoyl)-4-O-malonyl-quinic acid 3 which formed charge transfer complexes with the flavins in the XAD-fraction. As a model complex we examined the absorption behaviour of the complex between riboflavin and chlorogenic acid. Using the association constant, we calculated the absorption spectrum and could show that a complex between a flavin and a phenolic compound is a possible bluelight photoreceptor for the light-induced leaf opening in Albizia julibrissin.