HORSERADISH PEROXIDASE-CATALYZED CONJUGATION OF EUGENOL WITH BASIC-AMINO-ACIDS

L-Lysine is shown to yield an adduct with the quinone methide intermed iate formed during the horseradish peroxidase (HRP)-catalyzed aerobic oxidation of eugenol (4-allyl-2-methoxyphenol). Adduct formation is ev idenced by (i) lysine quenching of the characteristic quinone methide absorption band measured at 350 nm; arginine and gamma-aminobutyric ac id, but not alanine or propionic acid showed similar behaviour (ii) ly sine-promoted a 400 mV decrease of the eugenol oxidation voltammetric wave (1.00 V), concomitantly with an increase in current intensity and (iii) reverse phase HPLC isolation of the lysine eugenol adduct, foll owed by GCMS analysis. The MS spectrum is consistent with a 2:1 lysine :eugenol adduct (MW = 455). If operative in vivo, binding of lysine to eugenol might lead to protein inactivation and possibly be involved i n eugenol toxicity.