Disclosed is the use of the compounds of formula  wherein Q is —OH; —OR7; —NH2; —NHR7; —NR7R8; or —N═R9; T is —COR5; —CN; or —SO2—(C6-C12)aryl; R1 is hydrogen; —OR7, —SR7; —NHR7; —NR7R8; C1-C22alkyl; C2-C12Alkenyl; C2-C12alkinyl; C3-C12cycloalkyl; C3-C12cycloalkenyl; C7-C12aralkyl; C1-C12heteroalkyl, C2-C11heteroaralkyl; C6-C10aryl; or C1-C9heteroaryl; R2 and R3 independently from each other are C1-C22alkyl; C2-C12alkenyl; C2-C12alkinyl; C3-C12cycloalkyl, C3-C12cycloalkenyl; C7-C12aralkyl; C1-C12heteroalkyl; C3-C12cycloheteroalkyl; C2-C11heteroaralkyl, C6-C10aryl; or C1-C9heteroaryl; R4 is cyano; COR7, COOR7; CONH2; CONHR7; CONR7R8; SO2(C6-C12)aryl, C2-C12alk-1 -enyl; C3-C12cycloalk-1-enyl; C2-C12alk-1-inyl; C2-C12heteroalkyl, C3-C5heterocycloalkyl, C6-C10aryl; or C1-C9heteroaryl; R5 is —COR7; —COOR7; —OR7; —SR7, —NHR7, —NR7R8; C1-C22alkyl; C2-C12alkenyl; C2-C12alkinyl; C3-C12cycloalkyl; C3-C12cycloalkenyl; C7-C12aralkyl; C1-C12alkylphenyl; C1-C12alkoxy-C6-C10aryl; C1-C12heteroalkyl; C2-C11heteroaralkyl; C3-C12cycloheteroalkyl; C6-C10aryl; C1-C12alkoxy-C6-C10aryl or C1-C9heteroaryl; R6, R7 and R8 independently from each other are hydrogen; C1-C22alkyl; C2-C12alkenyl; C2-C12alkinyl; C3-C12cycloalkyl; C3-C12cycloalkenyl; C7-C12aralkyl; C1-C12heteroalkyl; C2-C11heteroaralkyl; C6-C10aryl; o-C6-C10aryl; or C1-C9heteroaryl; R9 is a (C1-C6)alkylidene radical; or R1 and R2, R1 and Q, R1 and R4, R1 and R6, R2 and R3, R3 and Q, R6 and Q, T and Q, each independently, are linked together, so that 1, 2, 3 or 4 carbocyclic or N, O and/or S-heterocyclic rings are formed, wherein each of them, independently from each other, may be condensed with an aromatic or heteroaromatic ring, and/or more N-, O- and/or S-heterocycic rings, and each N atom in a N-heterocyclic ring may be substituted by C1-C22alkyl; and n is a number from 1 to 4; for protecting of human hair and skin against the damaging effect of UV radiation.