Abstract
Antioxidants protect the structural and functional components in organisms against oxidative stress. Most antioxidants are of plant origin as the plants are permanently exposed to oxidative stress (UV radiation, photosynthetic reactions). Both carotenoids and flavonoids are prominent antioxidant and anti-radical agents often occurring together in the plant tissues and acting in lipophilic and hydrophilic milieu, respectively. They are complementary in their anti-radical activity. This study describes the synthesis of a series of hybrid ester conjugates of retinoic acid with various flavonolignans, such as silybin, 2,3-dehydrosilybin and isosilybin. Antioxidant/anti-radical activities and bio-physical properties of novel covalent carotenoid-flavonoid hybrids, as well as various mixtures of the respective parent components, were investigated. Retinoyl conjugates with silybin—which is the most important flavonolignan in silymarin complex—(and its pure diastereomers) displayed better 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity than both the parent compounds and their equimolar mixtures.
Highlights
Antioxidants are substances that protect the structural and functional components in living organisms—especially proteins, lipid structures and nucleic acids—against oxidative stress
The most important antioxidants include a number of vitamins and prominent bioactives such as carotenoids and flavonoids [3]
Due to the inherent sensitivity of carotenoids and flavonoids to oxidation under harsh conditions in organic syntheses, an enzymatic approach using the lipase Novozym 435® with a cross linker was first tested for the linking of carotenoids with flavonoids
Summary
Antioxidants are substances that protect the structural and functional components in living organisms—especially proteins, lipid structures (membranes) and nucleic acids—against oxidative stress. The concept of antioxidants as active redox species in vivo has been re-evaluated as a number of “antioxidants” act as Antioxidants 2019, 8, 236; doi:10.3390/antiox8070236 www.mdpi.com/journal/antioxidants
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