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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5454_Библиотеки_им_академика_М_И_Перельмана
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Flavonoids as Nutraceuticals. Rajesh K. Kesharwani, Deepika Saini, Raj K. Keservani, and
Anil Kumar Sharma (Eds.)
© 2024 Apple Academic Press, Inc. Co-published with CRC Press (Taylor & Francis)
CHAPTER 3
IMPORTANCE OF FLAVONOIDS IN
AGRICULTURE
NEHA SAINI, RITU KATARIA, ITTISHREE BHARDWAJ, and
PREETI PANCHAL
G.V.M. College of Pharmacy, Sonipat, Haryana, India
ABSTRACT
Flavonoids are important not only for their roles in floras but similarly for
their medicinal and nutraceutical applications. Flavonoids are a family of
plants that can be found in various concentrations in an inclusive range of
plant species. Flavonoids are secondary plant metabolites that play a key
part in the biological activity processes of plants. They are dependable for
the color characteristic of flowers and fruits. They also take part in symbiosis
between plants and microbes. Flavonoids are a class of bioactive chemicals
present in a wide range of plant-based foods. Flavonoids are classified into
subgroups that establish their chemical arrangement, containing flavones,
flavanones, flavonols, flavanonols, anthocyanins, and isoflavones. The
determinable and subjective examination of flavonoids has been supported
by the metabolomics technique. Flavonoids are a broad set of compounds
found in agricultural crops, and researchers have used metabolomics
technologies to examine flavonoid composition using various analytical
approaches. Allelopathy is currently studied as an organic management of
weeds and insect pests, as well as a way to alleviate stress and contamination
in consideration of boosting yield output in order to tackle many problems in
agriculture. The main objective of this study is to give an outline of their uses
and demonstrate that metabolomics is a useful means for studying flavonoid
metabolism in various agricultural crops.
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38 Flavonoids as Nutraceuticals
3.1 INTRODUCTION
The name “flavonoid” was coined from “flavous,” a Latin word that means
“yellow,” which resembles the color of flavonoid in ecology. Although their
name, many other flavonoids are white, and the most important flavonoid
-
related anthocyanins are purple, red, or blue in color. Flavonoids, also known
as bioflavonoids, are a class of secondary metabolites found in plants and
fungi (
Rana & Gulliya, 2019).
Secondary plant metabolites called avonoids are essential to the
biological activity of plants. They can be trusted to accurately predict the
colour of fruits and owers. Additionally, they participate in microbial and
plant symbiosis. These connections will be utilized to restrain weeds and
insects organically, as well as minimize stress and illness, to boost crop
yields (Tenango et al., 2017).
Flavonoids are low molar mass compounds with a polyphenolic structure
that are elaborate in photosynthesis and other biological functions in plants.
They frequently show defensive properties against biotic and abiotic stresses
such as Ultraviolet-B radiation, soil salinity, and water stress, detoxifying
reactive oxygen species (ROS), at least in part developed in Crops in stressful
circumstances (Shojaie et al., 2016).
Flavonoids are a class of unaffected essence that belongs to a group of plant
subordinate metabolites accompanying a polyphenolic form that is possibly
placed in the crop, edible part of the plant, and few liquors. They bear a sort of
advantageous biochemical and antioxidant possessions connected to afictions
like malignant growth, Mental disorder, and so forth (Panche et al., 2016).
The research for novel molecules with important physiological qualities
led to the study of avonoid chemistry, which occurred for most natural
products (Maraise et al., 2006). Flavonoids are a wide set of polyphenolic
chemicals with a benzo-pyrone structure that remain throughout plants. The
phenylpropanoid pathway is responsible for their production. Secondary
phenolic metabolites, such as avonoids, are thought to be responsible for a
wide range of pharmacological effects, according to research. Flavonoids are
phenolic hydroxylated compounds that are identied as generated by plants
in retort to contagious infection (Mondal & Rahman, 2020).
HPLC coupled to UV rays, mass, or nuclear magnetic resonance (NMR)
detectors can distinguish, evaluate, and identify avonoids in a single opera-
tion. The technique of capillary electrophoresis (CE) has recently gained
popularity (https://prezi.com/p/xrxs28nhrbvf/avonoids/?fallback=1).
Flavonoids are a class of bioactive chemicals present in a wide range
of plant-based foods. Flavonoids are classied into subgroups that establish
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Importance of Flavonoids in Agriculture 39
their chemical arrangement, containing avones, avanones, avonols,
avanonols, anthocyanins, and isoavones (Kazlowska & Wegierek,
2014).
3.2 CLASSIFICATION
Flavonoids various subclasses are explained below (Figure 3.1) with few
examples:
1. Flavonols: Flavonoids with a ketone group are recognized as flavo-
nols. Proanthocyanins are completed by these basic units. Flavonols
can be created in abundance in an extensive range of fruits and
vegetables. Kaempferol, quercetin, Rutin, myricetin, and fisetin are
the most explored flavonols. Flavonols are abundant in onions, broc
-
coli, lettuce, tomato, apples, grapes, and berries. Flavonols can also
be found in tea and red wine, in addition to fruits and vegetables.
2. Flavanones: These are also a major class of complexes that can
be present in some citrus fruits, including oranges, lemons, and
grapes. This set of flavonoids includes hesperidin, naringenin, and
eriodictyol. Because of their superoxide radicals' characteristics,
flavanones are associated with a variety of advantages that are
related to health. These compounds are present in citrus fruit juice
and peel, giving them a bitter taste. Citrus flavonoids have medicinal
properties that include antioxidants, anti-inflammatory, lipid levels,
and cholesterol-lowering.
3. Isoflavones: Isoflavonoids are a subgroup of flavonoids that make up
a significant and distinct subgroup. Isoflavonoids are mostly found
in soybeans and other leguminous plants, and their availability in the
kingdom Plantae is restricted. Certain isoflavonoids have also been
discovered in microbes. They are also identified to have an important
role as precursors for the synthesis of phytoalexins during plant-microbe
interactions. Isoflavonoids offer a lot of potential for treating diseases.
Isoflavones like genistein, Glycetin, and daidzein are commonly
referred to as phytoestrogens because of their estrogenic action.
4. Flavones: These are among the greatest prominent flavonoid
subclasses. Flavones are originated as glucosides in leaves, flowers,
and fruits of plants. Flavones can be found in parsley, celery, red
peppers, tea, peppermint, and ginkgo. This group of flavonoids
includes luteolin, apigenin, and tangeritin.
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40 Flavonoids as Nutraceuticals
5. Anthocyanins: These are pigments found in plants, flowers, and
fruits that give them their color. Cyanidin, delphinidin, Petunidin,
malvidin, proanthocyanidins (PAC), and peonidin are the most
studied anthocyanins. They’re typically located in the cranberry’s
outer cell layers. They are also present in red grapes, grapes, rasp
-
berries, strawberries, berries, and blackberries.
6. Flavan-3-Ols: Flavanonols are the 3-hydroxy precursors of flava-
nones, usually known as dihydroflavonols or catechins. They are a
multi-substituted and decidedly diverse subclass and include Epicat
-
echin Gallate, Catechin. Because the hydroxyl group is always
attached to the third position of the C ring, flavonols are also known
as flavan-3-ols. Bananas, apples, berries, apricots, and pears are high
in flavan-3-ols (Panche et al., 2016).
FIGURE 3.1 Classes of flavonoids.
Source: Adapted from: https://www.researchgate.net/figure/Classification-and-example-of-
flavonoids-and-their-chemical-structures-Flavonoids-are_fig3_301332394.
3.3 FUNCTION OF FLAVONOIDS IN PLANTS
Flavonoids are involved in a variety of biological processes in plants. Embryo
growth and development, fruit expansion and maturation, pollen tube germi-
nation, and hormonal transmission are all aided by them. Flavonoids have
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Importance of Flavonoids in Agriculture 41
antioxidant qualities in response to biotic and abiotic stimuli; they protect
against destruction caused by fungi, viruses, parasites, and Producers or
herbivores. They also have a role in floral, fruit, and seed pigment and color
variances. Flavonols, for example, are associated with the yellowish color,
flavanols with the color ochre to brownish, and anthocyanins with the color
reddish to purple. Anthocyanins and PACs are primarily being the reason
for the pigments in corn kernels and petunia flowers. These develop in the
nucleus or on the cell membrane. Anthocyanin build-up occurs in corn due
to vacuole sequestration (Tenango et al., 2017).
Flavonoids trigger a cascade of activities containing stress-persuaded
morphogenesis that defend plants from a variety of unanticipated lesions.
Flavonoids are vital for catalyzing electron transference and eliminating
reactive oxygen, notably in the manner of superoxide anions, hydroxyl
radicals, lipid peroxides, or hydroperoxides, as well as protecting life whole
from the detrimental belongings of oxidative processes in contact macromol-
ecules. They prevent the harmful effects of toxic chemicals on cells in this
way (Wagh et al., 2017).
3.4 ROLE OF FLAVONOIDS IN PLANTS (FIGURE 3.2)
FIGURE 3.2 Role of flavonoids in different fields.
Source: Reprinted from: Weston & Mathesius (2013). Copyright © 2013, Springer Science
Business Media
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42 Flavonoids as Nutraceuticals
3.4.1 AS GROWTH REGULATOR
Flavonoids provide important functional processes in plant-environment rela-
tionships. Auxin transport and its catabolism may be regulated by flavonoids
in the micromolar range. Flavonoids tendency to develop auxin gradients
results in phenotypic variants with various morphoanatomical characteris-
tics. Controlling auxin transport with flavonoids could be extremely useful
in stress-induced proliferation and differentiation responses in plants. When
comparing dihydroxy flavonoid-rich species to monohydroxy flavonoid-rich
species, phenotypes with markedly distinct morphological features develop.
In sunny areas, dwarfed hairy variants accompanying slight, tiny, and dense
leaves to direct light part of daytime transmittance are common, protecting
plants below in the canopies from light-induced intracellular homeostatic
disruptions. Shaded plants, on the other hand, have extended Internodes and
wide leaf lamina, as well as leaf senescence, since they are rich in flavonoid
compounds, i.e., apigenin, and have insignificant quantities of quercetin
derivatives (Kumar et al., 2013).
3.4.2 CROP YIELD AND PLANT GROWTH
Soil productivity has a direct relationship with plant development and
production. In agronomic terms, it refers to the soil’s ability to produce a
certain yield of agricultural crops. Though, a variety of aspects, including
soil physicochemical qualities and management-related factors, influence
soil ability. It is the ratio of inputs to outputs, which is connected to water and
fertilizer supply (inputs) vs crop yield in agronomic settings (output) (Mia et
al., 2010). These are in addition to these components, the phytomicrobiome
is increasingly being recognized as a vital component of crop productivity.
The land is home to a diverse range of microbial species, including unre-
stricted, symbiotic organisms, host-specific and non-host-specific microbes,
all of which can actually impact plant growth and productivity. About 1.0
g of soil is predicted to have 1 billion bacterial cells with 10,000 different
genes. Microbes obtain decreased carbon-rich food items secreted from
plant roots, while plants aid microorganisms in nutrient uptake, resistance
to disease, and stress management by direct and indirect mechanisms in the
phytomicrobiome. Numerous studies have established the significance of the
phytomicrobiome to crop yield and productivity.
Plants have a biosynthetic mechanism that produces hundreds of bio-
compounds that are needed to carry out essential tasks. Sugars, amino acids,
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43 Importance of Flavonoids in Agriculture
organic acids, phenolics, enzymes, and growth regulators are among the
substances released by the root system. Many microbes linked with the plant
root system use these secretions as a carbon and energy source (
Hijri, 2016).
3.4.3 COMBATING OXIDATIVE STRESS
Flavonoids have long been considered to serve a diversity of function in
plants. Various abiotic and natural determinants influence the result of sensi
-
tive oxygen variety (ROS) in plants, resulting in oxidative stress. Plants'
flavonoid production is almost entirely boosted by oxidative stress. They
bear the strength to take in ultimate forceful sunlight wavelengths (UV-B
and UV-A), limit ROS production, and quench ROS after they have formed.
Though early implant proceeds from the water to the land, flavonoids
performed key UV-B screening roles. The character of replacement ahead
of unconnected rings of flavonoids decide in consideration of antioxidant
ability to perform and talent to physically take in liquid UV wavelengths.
Flavonoids accompanying a dihydroxy B ring substituted bear a higher
antioxidant volume, while those accompanying a monohydroxy B ring
substituted bear a higher capability to consume UV wavelengths.
3.4.4 FLAVONOIDS IN RHIZOSPHERE
The rhizosphere is by far the most complicated and intense region for plants
to connect with their surroundings. The secretion of metabolic byproducts
comprising varied molecular weight organic and inorganic compounds such
as ions, phenolics, enzymes, secondary metabolites, and celluloses may
be required for maximum biological activity, nutrients uptake, and plants–
microbes interaction (
Pathan et al., 2010). Flavonoids are probable to be
radiated from plant root systems and have implicit effects on plant develop-
ment by facilitating rhizospheric relations, such as fascinating compatible
rhizosphere-dwelling rhizobia, stimulating mycorrhizal growth and hyphal
branching, increasing nutrient solubility, including phosphorus and iron, and
repelling pests and root pathogens (Mandal et al., 2010; Buer et al., 2007).
Flavonoid secretions from roots are thought to be accepted by ATP-
dependent active transport mediated by ABC transporters (Badri et al., 2008).
Flavonoids not only help to defend against damaging abiotic factors, but they
can also help to boost the concentration and bioavailability of soil nutritional
components in a low-nutrient environment. When nutrients are scarce in the
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44 Flavonoids as Nutraceuticals
soil, ABC transporters can release avonoids into the rhizosphere, where they
can bind with metals required for plant development and survival (Shaw et
al., 2006). Flavonoid production can be passive also as a result of root cap
and epidermal cell degradation (
Sugiyama et al., 2007). Flavonoid perma-
nence and mobility in the rhizosphere may be controlled by its solubility,
structure, microbial accessibility, and binding afnity, as these substances can
be adsorbed to soil or cell wall cation binding sites. Flavonoid glycosides are
water-insoluble and are believed to be less adsorbed to binding sites allowing
for greater exibility and accessibility (Shaw et al., 2006).
3.4.5 FLAVONOIDS AND LEGUME-RHIZOBIUM INTERACTION
Many studies have tried explaining and streamlining the connections that
occur among particular or specified plants and their symbionts. They have
attempted to clarify the contacts that occur between an individual or specific
species and their symbiotic organisms. In fact, these relationships are signifi-
cantly more complicated, including a variety of microorganisms linked with
a single plant that exchange chemical signals. These interactions, on the
other hand, benefit plants in a variety of ways. One of the most important
services offered by soil bacteria is soil fertility and nutrient uptake (Hassan
et al., 2012).
Nitrogen decit is a major issue in crop yields because of rapid nitrogen
loss from the soil due to leaching, denitrication, and immobilization. Atmo
-
spheric nitrogen is xed and becomes part of the soil nitrogen replenishment
by biological and synthetic mechanisms of xation from the atmosphere.
However, researchers and farmers have taken notice of the natural biological
xation of atmospheric nitrogen (N
2
), which accounts for around 60% of
total atmospheric nitrogen xation (Davidson, 2009). Signal exchange is
used as a form of interaction between the host and the symbiont for mutual
advantage in below-ground interactions that contribute to the creation of
legume nitrogen-xing symbioses. Root tips are at the source of rhizobium
attachment and infection, which frequently discharge the highest quantities
of avonoids. These secondary metabolites operate as signaling chemicals,
attracting rhizobia to plant roots and activating nod genes in the rhizobia,
which initiate the legumes modulation mechanism. Nitrogen-xing micro-
organisms, primarily Rhizobium and Bradyrhizobium, x over 50% of the
nitrogen necessary in legume crops, and the balance is provided by fertilizer
additives (Hartwig et al., 1991).
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45 Importance of Flavonoids in Agriculture
3.4.6 PLANT ABIOTIC STRESSES
Plants are vulnerable to a variety of unfavorable environmental circum-
stances since they are sessile. Plant hemostasis, physiology, and growth are
all affected by environmental fluctuations and harsh growing circumstances,
resulting in smaller and undersized plants. A variety of negative biotic and
abiotic stresses pose a threat to sustainable agriculture and are frequently
responsible for lower crop yields. Plant organs and tissues coordinate their
mechanisms for dealing with abiotic stressors. Chemical signals are used.
The majority of plant responses to stress situations are unknown. Biosyn
-
thetic flavonoids have gained significant attention for their capacity to
promote resistance to biotic and abiotic stresses. Abiotic stressors, including
UV radiation, salt, and drought tolerance, have significantly aided flavo-
noids as follows in the below points (Shah & Smith, 2020). Plants regulate
gene expression and provide a comprehensive method of control that further
regulates developmental stages when both biotic and abiotic stressors occur.
Transcription factors (TF) and their actions are one of the variables that
contribute to and aid gene transcription (
Muhammad et al., 2019).
3.4.6.1 UV SCAVENGERS: FLAVONOIDS
UV light is invisible, has a short wavelength, and is very powerful. These wave-
lengths have quite enough energy to break chemical bonds in plants, causing
damage and deformities through photochemical processes. UV-A, B, and C are
separated on the basis of different wavelengths of the light. UV-C is the most
energetic and can ionize specific compounds. UV-B can disturb plant metabo-
lism by influencing photosynthesis, starch concentration, and transpiration, as
well as causing cellular damage. For Example, Tomato flower/fruit coordina-
tion was shown to be increased under strong radiation with negligible influence
on vegetative plant components in a study conducted in sterile environmental
conditions. There was also an improvement in UV-B receptors and chlorophyll
content, as well as triterpenoid molecules that are UV absorption by-products
of antioxidant pathways. By stimulating oxidative pathways in plants, UV-A/B
can be employed as an abiotic stimulus to improve fruit quality.
3.4.6.2 ROLE OF FLAVONOIDS IN THE MANAGEMENT OF SALT
AND DROUGHT STRESS
Salinity is a key limitation to worldwide crop productivity and is one of the
most serious abiotic stresses. Excess soluble salts have an impact on nearly
20% of irrigated land. Natural and Anthropogenic activities have caused
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