Polyphenol ingredients and health effects of Green Oats: A brief update

Abstract

Green oat, also known as wild green oat, is a principal cultivated species harvested at their prime development stage, when still green and packed full of active functional nutrients, contributing to attenuating oxidative damage, reducing inflammatory reaction, hindering tumor progression and promoting cognitive health. The biological and physiological effects, to a large extent, are attributed to a variety of bioactive phytochemicals, encompassing β -glucan, dietary fiber as well as phenolic compounds, particularly Avenanthramides, the exclusive phenolic compounds in oats, demonstrating multiple and remarkable biological activities such as antioxidation, anti-inflammation, antineoplastic and immunomodulatory effects. In consideration of the promising edible and medicinal values, hence, this article will illustrate the underlying values in food and health of green oat, or its extracts, from the amounts and composition, biological effects concerned as well as the possible molecular mechanisms involved.

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Copyright: © 2024 International Society for Nutraceuticals and Functional Foods.
All rights reserved. 1
Review J. Food Bioact. 2024;000:000–000
Journal of
Food Bioactives International Society for
Nutraceuticals and Functional Foods
Polyphenol ingredients and health effects of Green Oats:
A brief update
Huilin Fang, Hui Zhao and Miao Li*
Tianjin Key Laboratory of Food and Biotechnology, School of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin
300134, China
*Corresponding author: Miao Li, Tianjin Key Laboratory of Food and Biotechnology, School of Biotechnology and Food Science, Tianjin
University of Commerce, Tianjin 300134, China. E-mail: limiao_hl@tjcu.edu.cn
DOI: 10.31665/JFB.2024.18377
Received: June 18, 2024; Revised received & accepted: June 30, 2024
Citation: Fang, H., Zhao, H., and Li, M. (2024). Polyphenol ingredients and health effects of Green Oats: A brief update. J. Food Bioact.
000: 000–000.
Abstract
Green Oats (Avena sativa L.), also known as “Avena Sativa”, are a type of cereal mainly grown in North America
and Europe. Green Oats are highly effective for targeting a broad spectrum of diseases. The beneficial effects
are largely due to various bioactive phytochemicals, such as β-glucan, dietary fiber, and phenolic compounds,
especially avenanthramides. These nutrients help reduce oxidative damage, inflammation, and tumor pro-
gression, and promote cognitive health. This review highlights the nutraceuticals and health-promoting val-
ues of green oat and its extracts, focusing on their compositions, biological effects, and underlying molecular
mechanisms.
Keywords: Green oat; Antioxidant; Avenanthramides; Anti-inflammation; Antineoplastic.
1. Introduction
Green oat (Ave na sativa L.), also known as Wild Green Oat, is
a species of wild and domesticated annual grasses in Gramineae
(Poaceae) family (Leggett, 1992). The genus Avena L. includes
29 to 31 species, with Avena sativa being the primary species
cultivated worldwide, particularly in the Western regions. As an
annual crop, oats have been cultivated for over 2000 years and
are consumed in countries such as China, the USA, Switzerland,
Denmark, Finland, Norway, and Sweden (Sang and Chu, 2017).
Green oat originated in Switzerland and has been included in
the German pharmacopoeia for over 200 years. As the fifth most
economically important cereal, green oat is grown in temperate
regions, particularly in North America and Europe (Peterson and
Murphy, 2000).
Beyond its use as a cereal, green oat has a long history of me-
dicinal use. People often eat the seed of green oats, the leaves and
stem (oat straw), and the oat bran (the outer layer of whole oats).
(Abascal and Yarnell, 2004; Reynertson et al., 2015). In recent dec-
ades, accumulating evidence indicates that green Oats are highly
effective for targeting a broad spectrum of diseases. The beneficial
effects are largely due to various bioactive phytochemicals, such
as β-glucan, dietary fiber, and phenolic compounds, especially av-
enanthramides (AVAs). These phytochemicals have been shown to
be effective in oxidative stress, inflammation, tumor progression,
hyperlipidemia, and cognitive health.
This brief review will be focused on our current understanding
of the main ingredients of green oats and the mechanisms of these
ingredients contributing to the health benefits of green oat.
2. Composition and effects of the polyphenol compounds in
Green Oats
Green Oats possess various bioactive ingredients including car-
bohydrates, protein, lipids, dietary fiber, vitamins, minerals, and
other bioactive substances, offer numerous health benefits by
reducing the risk of diseases such as hyperlipidemia, cardiovas-
cular diseases, and cancers. Among these bioactive ingredients,
polyphenols and their derivatives are not only abundant but also

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Polyphenol ingredients and health effects of Green Oats: A brief update Fang et al.
represent beneficial activities of green oats.
2.1. Phenolic compounds
Phenolic compounds, ranging from simple polyphenols to polym-
erized compounds, are a major class of secondary metabolites in
plants. In green oat, phenolic compounds include phenolic acids,
flavonoids, and others such as stilbenes and lignans (Figure 1). Oat
products are a rich source of polyphenols, with significant amounts
of phenolic acids. (Soycan et al., 2019). Major phenolic acids in
oat grains are hydroxybenzoic acids (e.g., protocatechuic, vanillic,
p-hydroxybenzoic, gallic, and syringic acids) and hydroxycinnam-
ic acids (e.g., ferulic, p-coumaric, o-coumaric, caffeic, and sinapic
acids) (Li et al., 2008).
The phenolic acids in green oats display broad health-promot-
ing effects. For example, ferulic acid inhibited tumor activity by
targeting fibroblast growth factor receptor 1-mediated angiogen-
esis (Yang et al., 2015). p-Coumaric acid has antibacterial, anti-
inflammatory, antioxidant, and antitumor effects by promoting
apoptosis and inhibiting cell proliferation. (Hu et al., 2020) (Lou
et al., 2012; Rafiee et al., 2020; Sharma et al., 2017). Gallic acid,
another phenolic compound, acts as a free radical scavenger and
inhibits cyclooxygenase-2 (COX-2) (Amaravani et al., 2012).
2.2. Avenanthramides
AVAs are exclusively found in oats and are the most abundant
phenolic alkaloids with significant physiological effects. Chemi-
cally, AVAs are amide conjugates of anthranilic acid and hydrox-
ycinnamic acids, with the three major types in oats being AVA 2p
(Avenanthramide A, Figure 2), AVA 2f (Avenanthramide B), and
AVA 2c (Avenanthramide C) (Figure 2). AVA 2c has the highest
total antioxidant capacity (Yang et al., 2014). AVAs are present
in all milling fractions and commercial oat products, being more
abundant in oat bran than other tissues (Xie et al., 2024). Further-
more, comparison of the AVA content from five oat samples indi-
cated that AVAs vary in different, species, growth stages, growth
conditions, and locations and levels of AVAs (2p, 2f, 2c in Figure
2) are significantly higher in groats than those in oat hulls (Xie
et al., 2024). In addition, Bratt et al suggested that the amount of
Figure 1. Composition and classification of polyphenols in Oat.

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Fang et al. Polyphenol ingredients and health effects of Green Oats: A brief update
the specific AVA is not correlated with its antioxidant activity, as
AVA 2c is not the most abundant while it is considered to have
the highest antioxidant capacity (Figure 3) (Bratt et al., 2003).
AVAs exhibit strong antioxidant activity against rancidification
and oxidation of polyunsaturated fatty acids in addition to bioac-
tivities such as anti-inflammation, and anti-neoplasm (Molteberg
et al., 1996) (Xue et al., 2021).
3. Effects and mechanisms of AVAs
3.1. Anti-oxidative stress
Oats are recognized as an excellent source of antioxidants (Pe-
ters, 1937). As the main bioactives of oats, AVAs exhibit highly
potent antioxidant properties both in vitro and in vivo. As for the
mechanisms of anti-oxidative stress, AVAs enhance the activity or
expression of antioxidant enzymes such as superoxide dismutase
(SOD), glutathione peroxidase (GPx), and catalase (CAT), thereby
defending against reactive oxygen species (ROS)-mediated inju-
ries (Figure 4) (Liu et al., 2011). In particular, AVA 2c reduces
H2O2-induced oxidative stress in human dermal fibroblasts by
regulating the activity of antioxidant enzymes (Wang and Eskiw,
2019). Clinical studies showed that AVA-enriched oat extracts sig-
nificantly increase plasma concentrations of reductive glutathione,
a key antioxidant (Chen et al., 2007). Long-term AVA supple-
mentation benefits health by reducing ROS and inflammatory cy-
tokines (Koenig et al., 2016).
3.2. Anti-inflammation
AVAs have been demonstrated to have anti-inflammatory proper-
ties in both histocytes (Kang et al., 2018) and immune cells (Dhakal
et al., 2019), and play a role in conditions such as hypersensitivity
(Sur et al., 2008) and neurodegenerative diseases (Wankhede et
al., 2023). They inhibit NF-κB-mediated inflammatory responses
by attenuating IKKβ phosphorylation, thus downregulating pro-
inflammatory cytokines (Figure 5) (Guo et al., 2008; Kang et al.,
2018). AVAs were able to modulate the Phosphoinositide 3-kinase
(PI3K) signaling pathway, which is implicated in the inflammatory
pathogenesis of neurodegenerative diseases like Parkinson’s and
Alzheimer’s diseases (Wankhede et al., 2023).
3.3. Antineoplastic activity
AVAs exhibit antineoplastic activity by inhibiting cell proliferation,
Figure 2. Molecular structure of the primary components of Avenanthramides.
Figure 3. Levels of AVAs in groats and hulls of oats.

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Polyphenol ingredients and health effects of Green Oats: A brief update Fang et al.
promoting apoptosis, and reducing inflammation in tumorigenesis
(Figure 6). They negatively regulate genes involved in survival and
angiogenesis, such as BIRC5, HIF1A, and VEGFA (Scarpa et al.,
2018). AVAs-enriched extracts were identified to inhibit the gen-
eration of COX-2/PGE2 in mouse peritoneal macrophages, which
establishes the inflammatory microenvironments and angiogenesis
Figure 4. Possible mechanism of the antioxidant effects of Avenanthramides.
Figure 5. Possible mechanism of the anti-inflammatory effects of Avenanthramides.
Figure 6. Possible mechanism of the antineoplastic activity of Avenanthramides.

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Fang et al. Polyphenol ingredients and health effects of Green Oats: A brief update
in cancer cells (Guo et al., 2010; Hashemi Goradel et al., 2019).
In addition, AVA 2c suppressed growth of colorectal cancer cells
through promoting senescence by attenuating β-catenin-mediated
transactivation (Fu et al., 2022).
4. Conclusion
Green oat is rich in bioactive nutrients which contribute to target
oxidative damage, inflammation, tumor progression, and promote
cognitive health. Oat extracts have shown significant biological
activities, making them a preferred source for chronic disease
prevention. Of its bioactive substances, polyphenols and AVAs
are not only abundant and heat-stable but also act as the bioac-
tive representatives of green oats. Thus, further research regarding
the bioactive mechanisms and development of processing of green
oat and its extracts, especially AVAs, will be essential to promote
the health and clinical translation of green oat- and/or green oat
extract-based products.
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