Biologically Active Polymers from Spontaneous Carotenoid Oxidation: A New Frontier in Carotenoid Activity

Abstract

In animals carotenoids show biological activity unrelated to vitamin A that has been considered to arise directly from the behavior of the parent compound, particularly as an antioxidant. However, the very property that confers antioxidant activity on some carotenoids in plants also confers susceptibility to oxidative transformation. As an alternative, it has been suggested that carotenoid oxidative breakdown or metabolic products could be the actual agents of activity in animals. However, an important and neglected aspect of the behavior of the highly unsaturated carotenoids is their potential to undergo addition of oxygen to form copolymers. Recently we reported that spontaneous oxidation of ß-carotene transforms it into a product dominated by ß-carotene-oxygen copolymers. We now report that the polymeric product is biologically active. Results suggest an overall ability to prime innate immune function to more rapidly respond to subsequent microbial challenges. An underlying structural resemblance to sporopollenin, found in the outer shell of spores and pollen, may allow the polymer to modulate innate immune responses through interactions with the pattern recognition receptor system. Oxygen copolymer formation appears common to all carotenoids, is anticipated to be widespread, and the products may contribute to the health benefits of carotenoid-rich fruits and vegetables.

Recent progress in understanding the molecular mechanisms of radioresistance in Deinococcus bacteria

“…Thus, oxygen-rich, ß caroteneoxygen copolymers might be responsible for the antioxidant properties of these compounds. The same study also states that these copolymers appear to be common to most, if not all carotenoid compounds (Johnston et al 2014). …”

Effect of oxidized β-carotene-oxygen copolymer compound on health and performance of pre- and post-weaned pigs

“…In Trial 1, the observation that the benefits of OxBC were most apparent during the starter period compared to the grower and finisher periods is not surprising, given that OxBC plays a role in supporting immunity (Burton et al, 2014; Duquette et al, 2014; Johnston et al, 2014) and the fact that young piglets experience high levels of stress associated with weaning and that they are immunologically immature. The highest incidence rates of diarrhea occurred during the starter period, consistent with the well-known susceptibility of young piglets to post-wean diarrhea (Rhouma et al, 2017).…”

“…We have previously reported that the spontaneous non-enzymatic oxidation of β-carotene produces predominantly an oxygen-rich copolymer compound with immunomodulatory properties (Burton et al, 2014; Johnston et al, 2014). Fully oxidized β-carotene, termed OxBC and rich in copolymer compound, exerts its actions on the immune system through pathways that are distinct from either vitamin A or intact β-carotene, which are both absent.…”

“…Fully oxidized β-carotene, termed OxBC and rich in copolymer compound, exerts its actions on the immune system through pathways that are distinct from either vitamin A or intact β-carotene, which are both absent. We have proposed that copolymer compounds are in fact the actual agents responsible for many of the provitamin A-independent activities of β-carotene and other carotenoids (Johnston et al, 2014).…”

“…OxBC exhibits dual immunological activities relating to: a) enhancing innate immune detection and response to pathogens (Johnston et al, 2014) and, b) an anti-inflammatory/pro-resolution action that limits the extent of over-zealous immune responses and reduces the level of background inflammation (Duquette et al, 2014; Chen et al, 2020).…”