Sensitized photooxidation of gamma-terpinene by Vitamin B2

JULIETA SACCHETTO; SANDRA MISKOSKI; NORMAN A. GARCÍA; WALTER MASSAD

Carlos Paz

Congreso; XIII Encuentro Latinoamericano de Fotoquímica y Fotobiología (ELAFOT); 2017

UNSE / UNC /UNLP

Flavoring and flavoring agents (Ars) are frequently used as food additives because of their ability to improve organoleptic properties and even enhance flavors. Another important characteristic of the Ars is given by their ability to act as antimicrobial agents by increasing the preservability of food [1]. In particular, γ-terpinene (γ-ter, Figure 1) is a volatile essential oil with antimicrobial properties, antioxidant and anti-inflammatory activities have been reported. It is used in food as an ingredient, in the production of peppermint and lemon essential oil, in the production of pharmaceutical drugs, and even in perfumes. On these bases, it is interesting to know the photostability of Ars that, in the event of light induced reactions, can be transformed and fail to meet or modify the specific functions for which they were employed. In this work we carried out a kinetic and mechanistic study about sensitized photooxidation of γ-ter with Riboflavin (Rf), a natural sensitizer that is a common ingredient in a great variety of foods. Preliminary assays on the visible light-irradiation of Rf + γ-ter showed that the substrate is degraded by the reaction with either electronically excited states of Rf or the reactive oxygen species (ROS), the latter generated from the triplet excited state of the Rf (3Rf*). The interaction between electronic singlet excited states of (1Rf*) and 3Rf* with γ-ter were studied by fluorescence and laser flash photolysis. Rate constant values of 2.18 x 109 M-1s-1 and 2.36 x 108 M-1s-1 were determined for the overall interaction of γ-ter with 1Rf* and 3Rf* respectively. Rose Bengal was used as sensitizer to study the participation of singlet oxygen (O2(1g)) in the degradation of γ-ter. Measurement of time resolved phosporescence quenching of O2(1g) and O2 uptake does not show any type of interaction between O2(1g) and γ-ter. In order to verify the participation of the other ROS sensitized by Rf, experiments of oxygen and substrate consumption were made in presence of specific inhibitors for different ROS. Only in the case of catalase significant changes were observed evidencing the participation of H2O2 in the degradation of γ-ter .Under aerobic sensitizing conditions the γ-ter oxidation is possible by either, reacting with 3Rf* or with H2O2, and this process could modify flavour and other properties of the compound.[1] L. L. Zaika. J. of Food Safety 1988, 9, 97?118.