The Multifunctional Roles of Polyphenols in Plant-Herbivore Interactions (original) (raw)

Plant Secondary Metabolites as Defense Tools against Herbivores for Sustainable Crop Protection

International Journal of Molecular Sciences, 2022

Plants have evolved several adaptive strategies through physiological changes in response to herbivore attacks. Plant secondary metabolites (PSMs) are synthesized to provide defensive functions and regulate defense signaling pathways to safeguard plants against herbivores. Herbivore injury initiates complex reactions which ultimately lead to synthesis and accumulation of PSMs. The biosynthesis of these metabolites is regulated by the interplay of signaling molecules comprising phytohormones. Plant volatile metabolites are released upon herbivore attack and are capable of directly inducing or priming hormonal defense signaling pathways. Secondary metabolites enable plants to quickly detect herbivore attacks and respond in a timely way in a rapidly changing scenario of pest and environment. Several studies have suggested that the potential for adaptation and/or resistance by insect herbivores to secondary metabolites is limited. These metabolites cause direct toxicity to insect pests,...

Resistance against Insect Pests by Plant Phenolics and their Derivative Compounds

The chemical nature of plant phenolics varies from a simple monomeric unit to highly polymerized structures of varying proportions of monomeric aglycon units. Phenolics are aromatic benzene ring compounds with one or more hydroxyl groups produced for protection against biotic stresses. The functions of phenolic compounds in plant physiology are difficult to overestimate. The phenolics provide structural integrity and scaffolding support to plants. Importantly, phenolic phytoalexin secreted by wounded or otherwise perturbed plants, repel or kill many insect pests. Insects represent adaptive characters that have been subjected to natural selection during evolution. Plants synthesize a greater array of secondary compounds than animals, since plants cannot rely on physical mobility to escape their predators and have therefore evolved a chemical defense against such predators. This article reviews the role of plant phenols and polyphenols, interactions and their concern to resistance mechanisms against the insect pest stresses.

Plant Defense and Insect Adaptation with Reference to Secondary Metabolites

Reference Series in Phytochemistry

Insects pose a great threat to plants, and plants, in turn, withstand to insect attack through various morphological and biochemical traits. Among the plant defensive traits, secondary metabolites play a major role against insect herbivory as they are highly dynamic. They either occur constitutively in plants or are induced in response to insect herbivory. These metabolites include sulfur-(terpenes and flavonoids) and nitrogen-containing metabolites (alkaloids, cyanogenic glucosides, and nonprotein amino acids), which are being implicated by plants against insect pests. Plant secondary metabolites either are directly toxic to insect pests or mediate signaling pathways that produce plant toxins. Further, some of the plant secondary metabolites act through antixenosis mode by developing non-preference in host plant to the insect pests. However, some plant secondary metabolites recruit natural enemies of the insect pests, thus indirectly defending plants against insect pests. However, insects have developed adaptations to these plant secondary metabolites. In this chapter, important plant secondary metabolites, their mechanism of action against insect pests, counter-adaptation by insects, and promising advances and challenges are discussed.

Plant Phenolics: Important Bio-Weapon against Pathogens and Insect Herbivores

Plants represent a rich source of nutrients for many organisms including bacteria, fungi, insects, and vertebrates. Although, immune system is absent in plants but they have structural, chemical, and protein-based defense system to detect invading organisms and stop them before they are able to cause extensive damage. In order to protect from disease and insects plants produce a large variety of secondary metabolites viz. phenolics, flavonoids, terpenes, and alkaloids. Phenols possessed a hydroxyl functional group on an aromatic ring. These compounds play an important role in plant defense system against pathogens and insect herbivores.

From Fighting Critters to Saving Lives: Polyphenols in Plant Defense and Human Health

International Journal of Molecular Sciences, 2021

Polyphenols, such as flavonoids and phenolic acids, are a group of specialized metabolites in plants that largely aid in plant defense by deterring biotic stressors and alleviating abiotic stress. Polyphenols offer a wide range of medical applications, acting as preventative and active treatments for diseases such as cancers and diabetes. Recently, researchers have proposed that polyphenols may contribute to certain applications aimed at tackling challenges related to the COVID-19 pandemic. Understanding the beneficial impacts of phytochemicals, such as polyphenols, could potentially help prepare society for future pandemics. Thus far, most reviews have focused on polyphenols in cancer prevention and treatment. This review aims to provide a comprehensive discussion on the critical roles that polyphenols play in both plant chemical defense and human health based on the most recent studies while highlighting prospective avenues for future research, as well as the implications for phyt...

Role of Polyphenols in the Resistance Mechanisms of Plants Against Fungal Pathogens and Insects

Phytochemistry

Plant phenolics are secondary metabolites that encompass several classes structurally diverse of natural products biogenetically arising from the shikimate-phenylpropanoids-flavonoids pathways. Plants need phenolic compounds for pigmentation, growth, reproduction, resistance to pathogens and for many other functions. Therefore, they represent adaptive characters that have been subjected to natural Correspondence/Reprint request: Prof.

Modern approaches to study plant–insect interactions in chemical ecology

Nature Reviews Chemistry, 2018

Phytochemical variation among plant species is one of the most fascinating and perplexing features of the natural world and has implications for both human health and the functioning of ecosystems. A key area of research on phytochemical variation has focused on insects that feed on plants and the enormous diversity of plant-derived compounds that reduce or deter damage by insects. Empirical studies on the ecology and evolution of these chemically mediated plant-insect interactions have been guided by a long history of theoretical development. However, until recently , such theory was substantially limited by inadequate data, a situation that is rapidly changing as ecologists partner with chemists utilizing the latest technological advances. In this Review , we aim to facilitate the union of ecological theory with modern chemistry by discussing important theoretical frameworks for studying chemical ecology and outlining the steps by which hypotheses on insect-phytochemical interactions can be advanced using current methodologies and statistical approaches. We highlight unique approaches to isolation, synthesis, spectroscopy , metabolomics and genomics relevant to chemical ecology and describe future areas for research that will bring an unprecedented understanding of phytochemical variation.

Phytochemical diversity and synergistic effects on herbivores

Phytochemistry Reviews, 2016

Synergistic effects of multiple plant secondary metabolites on upper trophic levels constitute an underexplored but potentially widespread component of coevolution and ecological interactions. Examples of plant secondary metabolites acting synergistically as insect deterrents are not common, and many studies focus on the pharmaceutical applications of natural products, where activity is serendipitous and not an evolved response. This review summarizes some systems that are ideal for testing synergistic plant defenses and utilizes a focused metaanalysis to examine studies that have tested effects of multiple compounds on insects. Due to a dearth of ecological synergy studies, one of the few patterns for synergy that we are able to report from the metaanalysis is that phytochemical mixtures have a larger overall effect on generalist herbivores than specialist herbivores. We recommend a focus on synergy in chemical ecology programs and suggest future hypothesis tests and methods. These approaches are not focused on techniques in molecular biology to examine mechanisms at the cellular level, rather we recommend uncovering the existence of synergy first, by combining the best methods in organic synthesis, isolation, chemical ecology, bioassays, and quantitative analyses. Data generated by our recommended methods should provide rigorous tests of important hypotheses on how intraclass and interclass compounds act synergistically to deter insects, disrupt the immune response, and ultimately contribute to diversification. Further synergy research should also contribute to determining if antiherbivore synergy is widespread among plant secondary metabolites, which would be consistent with the hypothesis that synergistic defenses are a key attribute of the evolved diverse chemical mixtures found in plants.