Structure-improving hair care agents

The use of vitamin B6 derivatives corresponding to formula (I):

• 3
• in which
• A and B independently of one another represent hydrogen, halogen, a C1-4 alkyl group, a C3-6 cycloalkyl group, a C1-4 monohydroxyalkyl group, a C2-4 oligohydroxyalkyl group, a C1-4 aminoalkyl group, a group —OR or a group —NR1R2, where R1 and R2 independently of one another represent hydrogen, a C1-4 alkyl group or a C1-4 monohydroxyalkyl group or R1 and R2 together with the nitrogen atom form a saturated ring,
• C represents a group —OR, —NR1R2, —OP(O)(OR3)2, a C1-4 monohydroxyalkyl group, a C2-4 oligohydroxyalkyl group or a C1-4 alkyl group,
• D represents a group —OR, a carboxy group, a C1-22 alkoxycarbonyl group, a formyl group, a group —CH2OR or a group —CH2—NR2,
• E represents a group —OR, —OP(O)(OR3)2, a C1-4 monohydroxyalkyl group or a C2-4 oligohydroxyalkyl group,
• R representing hydrogen, a C1-4 alkyl group, a C1-22 acyl group, a hydroxy-C2-22-acyl group, a C2-10 carboxyacyl group, a C3-10 oligocarboxyacyl group, an oligocarboxymonohydroxy-C3-10-acyl group, an oligocarboxyoligohydroxy-C3-10-acyl group, a C3-8 cycloalkyl group, a C1-4 monohydroxyalkyl group, a C2-4 oligohydroxyalkyl group, an aryl group which may contain a hydroxy, nitro or amino group, a heteroaromatic group or a group —CH2CH2NR1R2, where R1 and R2 are as defined above,
• R3 representing hydrogen or a C1-5 alkyl group,
• or one of the corresponding physiologically compatible salts, for improving the structure and strength of hair keratin and the fastness to washing of hair colors by topical application of preparations containing these derivatives/salts.