Structural chemistry and stability of anthocyanins

Abstract

Anthocyanins, which are natural pigments, are accountable for the deep blue, red, and purple hues of many fruits and vegetables. These pigments, which are a part of the flavonoid family, have garnered significant attention due to their potential health benefits such as antioxidant, anti-inflammatory, and anticancer properties. The biological activity and bioavailability of anthocyanins are determined by their chemical structure and stability. Anthocyanins are composed of a flavylium cation and have various substituents such as sugar and acyl groups that can impact their stability and reactivity. At low pH levels, anthocyanins are in their flavylium form and exhibit vivid colouration, but at higher pH levels, they undergo structural changes into quinoidal bases that are less stable and less colourful. The stability of anthocyanins can be influenced by several factors such as light, temperature, pH, and the existence of metal ions. Exposure to light and high temperatures may lead to anthocyanin degradation, whereas metal ions can create complexes that hinder their stability and bioavailability. Heating, drying, and extraction procedures can all have an impact on anthocyanin stability. In order to create successful preservation and processing methods for foods and supplements high in anthocyanins, comprehending their chemical structure and stability is crucial. With this objective in mind, the purpose of this review paper is to furnish a comprehensive outline of current knowledge regarding anthocyanin's structural chemistry and chemical stability. Significant factors that influence the stability and reactivity of anthocyanins will also be emphasized.