Biotransformation of ritalinic acid by laccase in the presence of mediator TEMPO.

Methylphenidate is widely used as a medication for the treatment of attention deficit hyperactivity disorder (ADHD) in children. Less than 1% of methylphenidate is excreted unchanged in urine, while 80% of an oral dose is excreted as ritalinic acid (which is reportedly poorly degradable). This study aims to investigate the biotransformation of ritalinic acid by free and immobilized enzymes. The influence of various laccase mediators on biotransformation efficiency has been tested. Formation of the main transformation products has been monitored and their potential structures suggested. The effective transformation of ritalinic acid was observed only in the presence of 2,2,6,6-tetramethylpiperidine 1-oxyl mediator (TEMPO). The most effective enzyme was the laccase of T. versicolor 159. The main transformation product was an N-methyl derivative of ritalinic acid. Ritalinic acid was also reduced to aldehyde and alcohol, and a broad spectrum of intermediate complexes with oxoammonium ion of TEMPO were detected. This is the first time the biotransformation of ritalinic acid has been investigated in detail.