Piperazine salts of hydroxycinnamic acids and hydroxystilbenes

The present invention relates to a method for stabilising the trans form of hydroxy-stilbenes or of hydroxy-cinnamic acids. Particularly, the present invention relates to compounds of general formula (I) with the trans configuration: (I) Wherein: R is selected from COOH and a group of formula (II): R1 is H, OH or R2, and R2 is independently selected from OH, linear or branched O- (C1-C6) alkyl optionally substituted with a group selected from OH or O- (C1-C6) alkyl; R3 is independently selected from H and linear or branched (C1-C6) alkyl optionally substituted with a group selected from OH or O- (C1-C6) alkyl. A method for the preparation thereof is also described.