Substituted pyridoxine-lactam carboxylate salts

A salt adduct comprising a positively charged moiety of formula (I):

• wherein
• R1 is straight or branched C1-C6 alkyl;
• R2 is selected from —OH, straight or branched C1-C6 alkoxy, and straight or branched C1-C6 alkoxycarbonyl;
• R3 and R4 are each independently selected from formyl and straight or branched C1-C6 alkyl optionally substituted by at least one halogen, amine, hydroxyl, C1-C6 alkoxy, thiol, or C1-C6 alkoxycarbonyl, and
• a carboxylated lactam ring is selected from the group consisting of:
• wherein
• R6 is selected from H, straight or branched C1-C6 alkyl optionally substituted at least one halogen, straight or branched C2-C6 alkenyl, straight or branched C2-C6 alkynyl, cycloalkyl, aryl and heteroaryl optionally substituted by a C1-C6 alkyl;
• R7, R8, R9, R10, R11, R12, R13 and R14 are each independently selected from H, straight or branched C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, cycloalkyl, aryl and heteroaryl optionally substituted by at least one group selected from C1-C6 alkyl, halogen, amino, cyano, nitro, thiol, C1-C6 alkoxy, aminocarbonyl, C1-C6 alkoxycarbonyl, C1-C6 carboxyalkyl, C1-C6 alkoxycarbonylalkyl and amidino, wherein the salt adduct is not metadoxine.