A method of using compounds of formula I in which the C═C double bond is present in E and/or Z configuration and the variables have the following meanings: R1 denotes COOR5, COR5, CONR5R6, CN, O═S(—R5)═O, O═S(═OR5)═O, R7O—P(—OR8)═O; R2 denotes COOR6, COR6, CONR5R6, CN, O═S(—R6)═O, O═S(═OR6)═O, R7O—P(—OR8)═O; R3 denotes hydrogen, an optionally substituted aliphatic, cycloaliphatic, araliphatic or aromatic radical having in each case up to 18 carbon atoms; R4 denotes an optionally substituted aromatic or heteroaromatic radical containing from 5 to 12 ring atoms; R5 to R8 independently denote hydrogen, an open-chain or branched-chain aliphatic, araliphatic, cycloaliphatic or optionally substituted aromatic radical containing in each case up to 18 carbon atoms, where the variables R3 to R8 may also form, together with the carbon atoms to which they are attached, a 5-membered or 6-membered ring, which may be anellated if desired, as UV filters, particularly UV-A filters, in cosmetic and pharmaceutical formulations for the protection of the human skin or human hair from solar radiation, alone or together with compounds known per se in cosmetic and pharmaceutical formulations and capable of absorbing radiation in the UV range.