SCAVENGING OF PHOTOGENERATED OXIDATIVE SPECIES BY OREGANO ESSENTIAL OIL AND THYMOL UNDER VISIBLE-LIGHT IRRADIATION

MUÑOZ, VANESA A.; FERRARI, GABRIELA V.; POSADAZ, ARIANA C.; GARCÍA, NORMAN A.; DIMARCO PALENCIA, FRIDA C. D..; MISKOSKI, SANDRA; MONTAÑA M. PAULINA

Mendoza

Congreso; XXXIV REUNIÓN CIENTÍFICA ANUAL DE LA SOCIEDAD DE BIOLOGÍA DE CUYO; 2016

Essential oils are a mixture of volatile secondary metabolites of plants. It is known that essential oils could be deteriorated losing its organoleptic and therapeutic properties. This degradation could be caused by different environmental factors, being one of the most important the light exposure in aerobic conditions, and generates allergenic compounds which could cause problems such as dermatitis, eczema, among others. These degradations may be caused by reactive oxygen species (ROS) photogenerated by reactions from endogenous sensitizers such as vitamin B2 (Riboflavin, Rf). We performed a systematic study on the sensitized photooxidation of oregano essential oil and thymol in order to establish the contribution of ROS in its degradation. In this scientific contribution we present a study of the kinetics and mechanisms involved in the degradation of oregano essential oil under visible light irradiation in the presence of Rf. The essential oil was extracted by hydrodistillation with a Clevenger trap from cultivated plants in the experimental field of FTU-UNSL, which were in flowering stage. The main components of this oil are carvacrol and thymol, two positional isomers of isopropylmethylphenol. The use of specific ROS scavengers indicates that thymol photodegradation is mainly caused by the presence of singlet molecular oxygen. We determine the rate constant of singlet molecular oxygen deactivation obtaining a value of 5,6x106 M-1 s-1 for both thymol and oregano essential oil. This result would point toward thymol is responsible of the deactivation of this oxidative species predominantly via a physical mechanism.