The Role of Polyphenols in Abiotic Stress Response: The Influence of Molecular Structure

Abstract

Abiotic stressors such as extreme temperatures, drought, flood, light, salt, and heavy metals alter biological diversity and crop production worldwide. Therefore, it is important to know the mechanisms by which plants cope with stress conditions. Polyphenols, which are the largest group of plant-specialized metabolites, are generally recognized as molecules involved in stress protection in plants. This diverse group of metabolites contains various structures, from simple forms consisting of one aromatic ring to more complex ones consisting of large number of polymerized molecules. Consequently, all these molecules, depending on their structure, may show different roles in plant growth, development, and stress protection. In the present review, we aimed to summarize data on how different polyphenol structures influence their biological activity and their roles in abiotic stress responses. We focused our review on phenolic acids, flavonoids, stilbenoids, and lignans.

Salinity Stress Alters the Secondary Metabolic Profile of M. sativa, M. arborea and Their Hybrid (Alborea)

“…Saponins of Medicago species are triterpenoid compounds and more than thirty-three different saponins containing one or more sugar chain units have been identified in M. sativa . Among them, medicagenic acid, hederagenin, zahnic acid and soyasapogenols A and B are the main saponins of M. sativa aerial parts [ 39 , 40 , 41 ]. Nevertheless, the content of medicagenic acid in several cases is higher in roots than in aerial parts [ 42 ].…”

“…The three polyphenols (caffeic acid, ferulic acid and cinnamic acid) belong to hydroxycinnamic acids (HCAs) and are all members of the biochemical pathway leading to lignin formation. Additionally, ferulic acid, apart from acting as an ROS scavenger, can positively regulate the activity of other scavenging enzymes and can also inhibit the expression of enzymes involved in ROS generation [ 39 , 40 ].…”

“…Several studies have highlighted that phenolic compounds maintain high antioxidant activity and are involved in ROS detoxification and prevention from oxidative damage under salt stress [ 53 , 54 , 55 ]. More specifically, lignans are involved in lignification and cell wall synthesis and they exhibit antioxidant capacity, thus they have a positive role in stress tolerance [ 39 , 56 , 57 ]. It is known that lignans have remarkable ecological functions in plants, providing protection against herbivores and microorganisms [ 58 ].…”

“…In several studies, salt tolerance was tightly linked to higher accumulation of phenolic compounds [ 60 , 61 , 62 ]. A very popular strategy to induce the production of several polyphenols is by application of stress hormones [ 39 , 43 ]. Given that M. arborea’s seedling growth was superior compared to the other two entries under acute stress it seems that its production of secondary metabolites, and in particular the production of saponins and polyphenols, had a positive effect under salt stress conditions without metabolic costs.…”

Photophysical Study and Biological Applications of Synthetic Chalcone-Based Fluorescent Dyes

“…Chalcones, α,β-unsaturated aromatic ketones, constitute the central skeleton of many important biological compounds [ 1 ] and are the biosynthetic precursors of flavonoids and isoflavonoids in plants [ 2 , 3 ]. Their diverse structures can cyclize to form various flavonoid compounds with different biological activities [ 4 , 5 ]. In the past decades, many synthetic analogues, such as aza-chalcones and chalcone derivatives containing isoxazole, pyrazole, and indole, [ 6 ] were developed and have shown interesting biological properties, such as antioxidant, anticancer, antimicrobial, antiprotozoal, antiulcer, antiviral, antihistaminic, anti-HIV, cytotoxic, and anti-inflammatory activities [ 7 , 8 , 9 ].…”