Anthocyanins: Biosynthesis, Distribution, Ecological Role, and Use of Biostimulants to Increase Their Content in Plant Foods—A Review

Abstract

In the past century, plant biostimulants have been increasingly used in agriculture as innovative and sustainable practice. Plant biostimulants have been mainly investigated as potential agents able to mitigate abiotic stress. However, few information is available about their ability to influence fruit quality or change fruit phytochemical composition. In particular, very little is known about their effects on anthocyanin synthesis and accumulation. Due to the increasing demand of consumers for healthier foods with high nutraceutical values, this review tries to fill the gap between anthocyanin content and biostimulant application. Here, we elucidate the chemical structure, biosynthetic pathway, plant distribution, and physiological role of anthocyanins in plants. Moreover, we discuss the potential implications for human health derived from the consumption of foods rich in these molecules. Finally, we report on literature data concerning the changes in anthocyanin content and profile after the application of biostimulant products on the most common anthocyanin-containing foods.

Proanthocyanidins and Where to Find Them: A Meta-Analytic Approach to Investigate Their Chemistry, Biosynthesis, Distribution, and Effect on Human Health

“…According to the number and position of hydroxyl groups, three main PACs may be identified: propelagordins (having a hydroxyl group alone); procyanidins (having two hydroxyl groups), and prodelphinidins (having three hydroxyl groups) ( Figure 1 B). The reason why these molecules have these names is due to the fact that, in an acid environment, they may be hydrolyzed, following the formation of the corresponding anthocyanins [ 15 ]. The generated compounds, differently from the original oligomers or polymers, have a characteristic color ranging between red and blue [ 15 ].…”

“…The reason why these molecules have these names is due to the fact that, in an acid environment, they may be hydrolyzed, following the formation of the corresponding anthocyanins [ 15 ]. The generated compounds, differently from the original oligomers or polymers, have a characteristic color ranging between red and blue [ 15 ]. Concerning the flavan-3-ol ring, since three carbons (C 2 , C 3 , and C 4 ) of the heterocycle are asymmetric, they may present different configurations.…”

“…At this point, leucocyanidin, leucopelargonidin, and leucodelphinidin can be converted into their respective anthocyanins by the anthocyanidin synthase (ANS) (EC 1.14.20.4) ( Figure 6 ). This reaction allows the formation of the key compounds that may alternatively enter into biosynthetic pathway of anthocyanins, in which the anthocyanin scaffold may be further modified through different enzymatic modifications, including methylation, acetylation, and glycosylation [ 15 , 33 ]. However, anthocyanins may be converted into the respective colorless 2R,3R-flavan-3-ols by the double reduction operated by the anthocyanidin reductase (ANR) (EC 1.3.1.77).…”

“…Generally, these phenomena lead to the overproduction of reactive oxygen (ROS) and nitrogen (RNS) species, and then in oxidative stress [ 44 ]. ROS and RNS are very dangerous molecules for both animal and plant cells, as they are highly reactive and capable of compromising the normal function of a large class of biomolecules, including proteins, lipids, and nucleic acids [ 15 , 44 ]. In order to counteract the overproduction of ROS and RNS, during both biotic and abiotic stresses, the normal physiological functions of plants are alternated, and in particular, specific metabolic pathways are activated, resulting in the biosynthesis of both non-enzymatic antioxidants, such as ascorbic acid, flavonols, glutathione and various pigments, and/or enzymatic defenses [ 15 ].…”

“…ROS and RNS are very dangerous molecules for both animal and plant cells, as they are highly reactive and capable of compromising the normal function of a large class of biomolecules, including proteins, lipids, and nucleic acids [ 15 , 44 ]. In order to counteract the overproduction of ROS and RNS, during both biotic and abiotic stresses, the normal physiological functions of plants are alternated, and in particular, specific metabolic pathways are activated, resulting in the biosynthesis of both non-enzymatic antioxidants, such as ascorbic acid, flavonols, glutathione and various pigments, and/or enzymatic defenses [ 15 ]. Plant cells, unlike animal ones, are characterized by the presence of a large central vacuole where antioxidant flavonoids are accumulated, including PACs [ 45 ].…”