PHYTOALEXINS
 
   

Phytoalexins

This section was compiled by Frank M. Painter, D.C.
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  Frankp@chiro.org

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Conditions That Respond Alternative Medicine Approaches to Disease
 
   

It’s been 8 years since I first stumbled upon a class of protective nutrients called phytoalexins, while I was researching the benefits of organic produce. [1]   These unique compounds rarely appear in conventionally grown fruits and vegetables; they are only found at appreciable levels in organic produce.   [2]

This is because plants only produce these powerful phytochemicals as a defensive “immune response” to an assault by bugs, bacteria, viruses, molds, or mildews.)   Without some external threat stimulus, the plant has no need to produce them.

They are also referred to as secondary metabolites, because they are “organic compounds that are not directly involved in the normal growth, development, or reproduction of the plant”.

Biologists have named this defensive plant mechanism Induced Systemic Resistance, and this response has recognized for more than 60 years. However, it is only recently that the health-promotional effects of these nutrients have been seriously considered.   [3]   [4]

 
   

Phytoalexin Articles
 
   

The ORAC of Organic and the Promise of Phyto-alexins
New Hope | May 31, 2009 ~ FULL TEXT

Phyto-alexins are low molecular-weight compounds that accumulate in plants in response to infection, wounding, freezing, UV light and micro-organisms. [3] These processes, also known as Induced Systemic Resistance (ISR) of plants against pathogens, are a widespread phenomenon, but only recently have the potential health benefits been recognised. Even less characterised is the impact of farming methods, and more specifically organic farming methods, resulting in altered levels of phyto-alexins.

 
   

Phytoalexin Abstracts
 
   

An Update on the Effects of Glyceollins on Human Health:
Possible Anticancer Effects and Underlying Mechanisms

Nutrients. 2019 (Jan 3);   11 (1).  pii: E79 ~ FULL TEXT

Biologically active plant-based compounds, commonly referred to as phytochemicals, can influence the expression and function of various receptors and transcription factors or signaling pathways that play vital roles in cellular functions and are then involved in human health and diseases. Thus, phytochemicals may have a great potential to prevent and treat chronic diseases. Glyceollins, a group of phytoalexins that are isolated from soybeans, have attracted attention because they exert numerous effects on human functions and diseases, notably anticancer effects. In this review, we have presented an update on the effects of glyceollins in relation to their potential beneficial roles in human health. Despite a growing number of studies suggesting that this new family of phytochemicals can be involved in critical cellular pathways, such as estrogen receptor, protein kinase, and lipid kinase signaling pathways, future investigations will be needed to better understand their molecular mechanisms and their specific significance in biomedical applications.

Biological Activities of Stilbenoids
Int J Mol Sci. 2018 (Mar 9);   19 (3):   E792 ~ FULL TEXT

Stilbenoids are a group of naturally occurring phenolic compounds found in various plant species. They share a common backbone structure known as stilbene, but differ in the nature and position of substituents. Stilbenoids are classified as phytoalexins, which are antimicrobial compounds produced de novo in plants to protect against fungal infection and toxins. In this review, the biological effects of stilbenoids such as resveratrol, pterostilbene, gnetol and piceatannol are discussed. Stilbenoids exert various biological activities ranging from cardioprotection, neuroprotection, anti-diabetic properties, depigmentation, anti-inflammation, cancer prevention and treatment. The results presented cover a myriad of models, from cell culture to animal studies as well as clinical human trials. Although positive results were obtained in most cell culture and animal studies, further human studies are needed to substantiate beneficial effects of stilbenoids. Resveratrol remains the most widely studied stilbenoid. However, there is limited information regarding the potential of less common stilbenoids. Therefore, further research is warranted to evaluate the salutary effects of various stilbenoids.

Soybean-Derived Phytoalexins Improve Cognitive Function through Activation
of Nrf2/HO-1 Signaling Pathway

Int J Mol Sci. 2018 (Jan 16);   19 (1).   pii: E268 ~ FULL TEXT

As soy-derived glyceollins are known to induce antioxidant enzymes in various types of cells and tissues, we hypothesized that the compounds could protect neurons from damage due to reactive oxygen species (ROS). In order to examine the neuroprotective effect of glyceollins, primary cortical neurons collected from mice and mouse hippocampal HT22 cells were challenged with glutamate. Glyceollins attenuated glutamate-induced cytotoxicity in primary cortical neuron isolated from mice carrying wild-type nuclear factor (erythroid-derived 2)-like 2 (Nrf2), but the compounds were ineffective in those isolated from Nrf2 knockout mice, suggesting the involvement of the Nrf2 signaling pathway in glyceollin-mediated neuroprotection. Furthermore, the inhibition of heme oxygenase-1 (HO-1), a major downstream enzyme of Nrf2, abolished the suppressive effect of glyceollins against glutamate-induced ROS production and cytotoxicity, confirming that activation of HO-1 by glyceollins is responsible for the neuroprotection.

Resveratrol Requires Red Wine Polyphenols for Optimum Antioxidant Activity
Journal of Nutrition, Health & Aging 2016;   20 (5):   540–545 ~ FULL TEXT

Overall, our results demonstrate that resveratrol and red wine polyphenols together can protect mammalian cells from oxidative stress, whereas resveratrol alone may have pro-oxidant or anti-oxidant effects depending on concentration. This conclusion is in line with the hypothesis that the benefits of diets rich in fruits and vegetables are attributable to the uptake of phytocomplexes rather than to individual micro-compounds. Several authors have hypothesized that some health effects of plant polyphenols may not require their efficient absorption through the gut and may be due to the direct, protective effects on the intestinal mucosa against oxidative stress or the action of carcinogens. [41] Studies on human cells show that polyphenols can protect skin fibroblasts and keratinocytes from photo-radiation damage [42]; that resveratrol protects cells from an oxidative stress by tert-butylhydroperoxide only at high concentrations (in the micromolar range [43]); and that the protection is enhanced if resveratrol is used in combination with polyphenols such as quercetina and pterostilbene. [44]

An Overview of Plant Phenolic Compounds and Their Importance
in Human Nutrition and Management of Type 2 Diabetes

Molecules. 2016 (Oct 15);   21 (10).   pii: E1374 ~ FULL TEXT

phenylpropanoid pathways. Plant phenolic compounds can act as antioxidants, structural polymers (lignin), attractants (flavonoids and carotenoids), UV screens (flavonoids), signal compounds (salicylic acid, flavonoids) and defense response chemicals (tannins, phytoalexins). From a human physiological standpoint, phenolic compounds are vital in defense responses, such as anti-aging, anti-inflammatory, antioxidant and anti-proliferative activities. Therefore, it is beneficial to eat such plant foods that have a high antioxidant compound content, which will cut down the incidence of certain chronic diseases, for instance diabetes, cancers and cardiovascular diseases, through the management of oxidative stress. Furthermore, berries and other fruits with low-amylase and high-glucosidase inhibitory activities could be thought of as candidate food items in the control of the early stages of hyperglycemia associated with type 2 diabetes.

Deciphering the Role of Phytoalexins in Plant-microorganism Interactions
and Human Health

Molecules. 2014 (Nov 5);   19 (11):   18033–18056 ~ FULL TEXT

Phytoalexins are low molecular weight antimicrobial compounds that are produced by plants as a response to biotic and abiotic stresses. As such they take part in an intricate defense system which enables plants to control invading microorganisms. In this review we present the key features of this diverse group of molecules, namely their chemical structures, biosynthesis, regulatory mechanisms, biological activities, metabolism and molecular engineering.

Phytoalexins in Cancer Prevention
Frontiers in Bioscience (Landmark Ed). 2012 (Jun 1);   17:   2035–2058 ~ FULL TEXT

Plant phytoalexins are a class of low molecular weight compounds that accumulate in response to biotic and abiotic elicitors such as pathogens, wounding, freezing, UV light, and exposure to agricultural chemicals. Phytoalexins have been identified in at least 75 plants including cruciferous vegetables, soybean, garlic, tomato, rice, beans, and potatoes suggesting plants may be a rich source of cancer-fighting compounds. Preclinical evidence suggests these compounds possess anticancer properties including an inhibition of microbial activity, cell proliferation, invasion and metastasis, hormonal stimulation, and stimulatory effects on expression of metabolizing enzymes. This review highlights the plausible molecular mechanisms through which phytoalexins regulate biological processes that can impinge cancer development. Targets of phytoalexins include signal transduction pathways, transcription factors, cell cycle checkpoints, intrinsic and extrinsic apoptotic pathways, cell invasion and matrix metalloproteinase, nuclear receptors, and the phase II detoxification pathway. Additional research should address physiological relevant dietary concentrations, combinations of phytoalexins and interactions with other dietary compounds, duration of exposure, and tissue specificity as variables that influence the effectiveness of phytoalexins on normal and cancerous processes.

Soyabean Glyceollins: Biological Effects and Relevance to Human Health
Proc Nutr Soc. 2012 (Feb);   71 (1):   166–174 ~ FULL TEXT

Glyceollins, one family of phytoalexins, are de novo synthesised from daidzein in the soyabean upon exposure to some types of fungus. The efficiency of glyceollin production appears to be influenced by soyabean variety, fungal species, and the degree of physical damage to the soyabean. The compounds have been shown to have strong antioxidant and anti-inflammatory activities, and to inhibit the proliferation and migration of human aortic smooth muscle cells, suggesting their potential to prevent atherosclerosis. It has also been reported that glyceollins have inhibited the growth of prostate and breast cancer cells in xenograft animal models, which is probably due to their anti-oestrogenic activity. In essence, glyceollins deserve further animal and clinical studies to confirm their health benefits.

Phytoalexins in Defense Against Pathogens
Trends in Plant Science 2012 (Feb);   17 (2):   73–90 ~ FULL TEXT

Plants use an intricate defense system against pests and pathogens, including the production of low molecular mass secondary metabolites with antimicrobial activity, which are synthesized de novo after stress and are collectively known as phytoalexins. In this review, we focus on the biosynthesis and regulation of camalexin, and its role in plant defense. In addition, we detail some of the phytoalexins produced by a range of crop plants from Brassicaceae, Fabaceae, Solanaceae, Vitaceae and Poaceae. This includes the very recently identified kauralexins and zealexins produced by maize, and the biosynthesis and regulation of phytoalexins produced by rice. Molecular approaches are helping to unravel some of the mechanisms and reveal the complexity of these bioactive compounds, including phytoalexin action and metabolism.

Phytoalexin-enriched Functional Foods
J Agric Food Chem. 2009 (Apr 8);   57 (7):   2614–2622 ~ FULL TEXT

Functional foods have been a developing area of food science research for the past decade. Many foods are derived from plants that naturally contain compounds beneficial to human health and can often prevent certain diseases. Plants containing phytochemicals with potent anticancer and antioxidant activities have spurred development of many new functional foods. This has led to the creation of functional foods to target health problems such as obesity and inflammation. More recent research into the use of plant phytoalexins as nutritional components has opened up a new area of food science.


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