The Multifunctional Roles of Polyphenols in Plant-Herbivore Interactions

Abstract

There is no argument to the fact that insect herbivores cause significant losses to plant productivity in both natural and agricultural ecosystems. To counter this continuous onslaught, plants have evolved a suite of direct and indirect, constitutive and induced, chemical and physical defenses, and secondary metabolites are a key group that facilitates these defenses. Polyphenols—widely distributed in flowering plants—are the major group of such biologically active secondary metabolites. Recent advances in analytical chemistry and metabolomics have provided an opportunity to dig deep into extraction and quantification of plant-based natural products with insecticidal/insect deterrent activity, a potential sustainable pest management strategy. However, we currently lack an updated review of their multifunctional roles in insect-plant interactions, especially focusing on their insect deterrent or antifeedant properties. This review focuses on the role of polyphenols in plant-insect interactions and plant defenses including their structure, induction, regulation, and their anti-feeding and toxicity effects. Details on mechanisms underlying these interactions and localization of these compounds are discussed in the context of insect-plant interactions, current findings, and potential avenues for future research in this area.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

“…In plant defense systems, isoflavones serve as stress-resistant mediators with antioxidant activity that help neutralize reactive oxygen species (ROS) induced by stressful conditions. They are precursors of phytoalexins, a classic plant metabolite with antibacterial and antiviral effects and/or antiherbivore activities that protect plants from pathogen infections (Figure 3) [26,[29][30][31][32]. One of the most well-known soybean phytoalexins is prenylated pterocarpans derived from glyceollins and daidzein, which are released in response to pathogens, such as Phytophthora sojae and Macrophomina phaseolina [33].…”

“…Relationship between isoflavone products and antimicrobial activity. Phenylalaninederived biosynthetic isoflavone products, including 6"-O-malonylgenistein, glyceollins (I, II, and III), coumestan, isoflavan, and pterocarpan, are capable of antimicrobial and antiherbivore activity for defense against abiotic stress, such as pathogens [29][30][31][32].…”

Quercetin and Rutin as Modifiers of Aphid Probing Behavior

“…This is often achieved by the use of antifeedants or attractants, especially in the 'push-pull' strategies [15][16][17][18]. The most potent aphid behavior modifying chemicals come from natural sources and represent various groups of secondary plant Molecules 2021, 26, 3622 2 of 11 compounds including flavonoids [11,12,[19][20][21]. The synthesis of flavonoids in plants is also induced by herbivore attack including aphid infestation [21][22][23].…”

“…Rutin and its aglycone quercetin are well-known plant flavonoids that mediate insectplant relationships and are parts of constitutive and induced plant resistance mechanisms [21,[24][25][26]. However, each of these flavonols causes different effects on insect behavior depending on the insect and plant species involved.…”

A robust method of extraction and GC-MS analysis of Monophenols exhibited UV-B mediated accumulation in Arabidopsis

“…(Fang et al, 2019) Metabolites like alkaloids, terpenoids, phenolics, anthocyanins, coumarins and others support secondary metabolism leading to an array of phytochemicals that play specific roles like protection under stress. Among these the phenolics, confer chemical-biological roles supporting growth, development and protection under stress (Bueno et al, 2012) (Singh et al, 2021). Accumulation of phenolics is spatial, temporal and stimuli regulated and can be specific to tissue types, species, and developmental stages (Barros et al, 2012) (Lingwan et al, 2020).…”