The formation of epoxides as a product of the terpene ozonolysis has a few mentions in the literature. However, it is fairly common during the oxidation of carotenoids. The attack on the molecule tends to find more be in positions 5,6 or 5′,6´ in carotenoids which have a β-ionone ring. This preference is due to the fact that terminal double bonds

have high electronic densities and, consequently, favour the attack of the electrophilic species (Chichester and McFeeters, 1971). To the best of our knowledge, this work is the first to examine compounds originating from the oxidation of carotenoids that have an epoxy function in the β-ionone ring and a carbonyl function in the main chain.β-Apo-acid-carotenoids

may also be formed during β-carotene oxidation. In this study, the compounds 5,9,13,13-tetramethyl-12,17-dioxo-octadec-2,4,6,8,10-pentenoic and pyruvic acid were tentatively identified, with the latter compound being the most abundant product. Pyruvic acid, which is considered to be a secondary product in the ozonolysis of β-carotene, was found in the chromatogram as two peaks that were eluted during distinct retention times (8.0 and 9.4 min). Duvelisib price The sin and anti isomers, which are eluted at 8.0 and 9.4 min, respectively, were likely responsible for these two peaks. Both peaks were tentatively identified using mass spectrometry, through the 267 ion which is characteristic of the [M–H]− fragment from the corresponding hydrazone. Pyruvic acid could have been formed either by the direct ozonolysis of β-carotene or from its primary oxidation products. One of the possible pathways for the formation of pyruvic acid is shown in Fig. 4. Initially, the ozone reacts with the C9–C10 double bond of β-carotene, resulting in an ozonide

which then gives rise to β-ionone and a Crieege’s biradical. A new reaction then occurs with ozone in the C7–C8 double bond of β-ionone, which forms the mono and dicarbonyls β-cyclocitral and methyl Elongation factor 2 kinase glyoxal, respectively, and the corresponding Crieege’s biradicals 1 and 2. In this pathway, pyruvic acid is then formed from a rearrangement of Crieege’s biradical 1. The present study suggests that other intermediary products, such as 15-apo-β-carotenal and 3,7,11,11-tetramethyl-10,15-dioxo-hexadec-2,4,6,8-tetraenal, both of which are highly reactive species, are prone to subsequent oxidation. New products, such as pyruvic acid, may be then formed during this further oxidation. Fig.