When I first learned about Nrf2 activators in early 2012, I became quite enthusiastic about new knowledge that natural substances called polyphenolic compounds had the ability to activate this transcription factor. Once released in the cell Nrf2 can migrate to the nucleus and cause the body to endogenously produce high levels of key protective/antioxidant enzymes.

Also, I actively began the development of a product called Ultimate Protector that contains many concentrates and extracts from fruits, vegetables, and herbs. This product functions as 1) an excellent source of many Nrf2 activators, 2) a source of powerful antioxidants exhibiting an extremely high ORAC5.0 value per serving, and 3) a source of non-GMO Vitamin C.

More recently (July 2019) I have updated the product to Ultimate Protector+ that contains some exciting new ingredients that are now available on the market including SFB® (Standardized Fruit Blend) that contains among others mangosteen, goji berry, pomegranate, and apple extracts (click on the ingredient name to see detailed blog articles concerning these). In addition, I have added significant amounts of ingredients that are well known as potent Nrf2 activators and antioxidants including Green Tea extract and VinCare® whole grape extract.

New Ultimate Protector+

It is interesting to note that over 16 years ago I formulated a wonderful antioxidant formula called PRO-C™. PRO-C™ contains Buffered Vitamin C (in the form of powdered calcium, magnesium, and zinc ascorbates), high-potency Grape Extract (from grape pulp, skins, and seeds), Green Tea Extract, reduced Glutathione, N-Acetyl-L-Cysteine (NAC), R-Lipoic Acid, coenzyme forms of Vitamin B2 and Vitamin B6, and Selenium.

PRO-C™ has been one of the most effective products at supporting health I have ever formulated. Our current knowledge shows that PRO-C™ contains four effective Nrf2 activators, selenium needed for glutathione peroxidase functioning, Vitamin B2 and Vitamin B6 that support the effectiveness of glutathione, and antioxidants including Vitamin C and glutathione. I recently wrote a blog article titled PRO-C™ SUPER ANTIOXIDANT FORMULA that provides details concerning this formula.

My current personal list of supplements that I (and my wife) take every day includes both Ultimate Protector+™ and PRO-C™. We feel gifted to have these products available to us!!

In this article, I will provide greater insight into the natural sources of Nrf2 activators and how they perform in the body.

SOME KEY ENZYMES MODULATED BY Nrf2 ACTIVATORS

Activation of Nrf2 results in the induction of many cytoprotective proteins. We have seen articles that claim over 200 different enzymes can be produced in the body by Nrf2 activators, but have also seen reference that over 4,000 enzymes may be produced!  Examples of some of the key enzymes are shown below:

• NAD(P)H quinone oxidoreductase 1 – a prototypical Nrf2 target gene that catalyzes the reduction and detoxification of highly reactive quinones that can cause redox cycling and oxidative stress.
• Superoxide dismutases (SOD) – enzymes that catalyze the dismutation of superoxide (O₂⁻) into oxygen and hydrogen peroxide. Thus, they are an important antioxidant defense in nearly all cells exposed to oxygen where superoxide is one of the main reactive oxygen species. SOD is known to provide powerful antinflammatory activity.
• Glutamate-cysteine ligase which is the rate-limiting step in the synthesis of glutathione (GSH), a very powerful endogenous antioxidant. Glutamate-cysteine ligase is a characteristic Nrf2 target gene, which establishes Nrf2 as a regulator of glutathione, one of the most important antioxidants in the body.
• Heme oxygenase-1 (HO-1) is an enzyme that catalyzes the breakdown of heme into the antioxidant biliverdin, the anti-inflammatory agent carbon monoxide, and iron. HO-1 is a Nrf2 target gene that has been shown to protect from a variety of pathologies, including sepsis, hypertension, atherosclerosis, acute lung injury, kidney injury, and pain.
• The glutathione S-transferase (GST) family includes cytosolic, mitochondrial, and microsomal enzymes that catalyze the conjugation of GSH with endogenous and xenobiotic electrophiles. After detoxification by GSH conjugation catalyzed by GSTs, the body can eliminate potentially harmful and toxic compounds. GSTs are induced by Nrf2 activation and represent an important route of detoxification.
• The UDP-glucuronosyltransferas (UGT) family catalyze the conjugation of a glucuronic acid moiety to a variety of endogenous and exogenous substances, making them more water soluble and readily excreted. Important substrates for glucuronidation include bilirubin, and acetaminophen. Nrf2 has been shown to induce UGT1A1 and UGT1A6.
• Multidrug resistance-associated proteins  (Mrps) are important membrane transporters that efflux various compounds from various organs and into bile or plasma, with subsequent excretion in the feces or urine, respectively. Mrps have been shown to be upregulated by Nrf2 and alteration in their expression can dramatically alter the pharmacokinetics and toxicity of compounds.

NATURAL FOODS AND FOOD EXTRACTS PROMOTE THE EXPRESSION OF Nrf2

The March 2011 Epub Biochemical Basis for Functional Ingredient Design from Fruits reports: “Functional food ingredients (nutraceuticals) in fruits range from small molecular components, such as the secondary plant products, to macromolecular entities, e.g., pectin and cellulose, that provide several health benefits.  In fruits, the most visible functional ingredients are the color components anthocyanins and carotenoids.

“In addition, several other secondary plant products, including terpenes, show health beneficial activities.  A common feature of several functional ingredients is their antioxidant function. For example, reactive oxygen species (ROS) can be oxidized and stabilized by flavonoid components, and the flavonoid radical can undergo electron rearrangement stabilizing the flavonoid radical.  Compounds that possess an orthodihydroxy or quinone structure can interact with cellular proteins in the Keap1/Nrf2/ARE pathway to activate the transcription of antioxidant enzymes.

“Carotenoids and flavonoids can also exert their action by modulating the signal transduction and gene expression within the cell. Recent results suggest that these activities are primarily responsible for the health benefits associated with the consumption of fruits and vegetables.”

One of the interesting aspects of the extensive research that has been conducted is the fact that many of the polyphenols that have been shown to activate Nrf2 have been used in natural healing formulas for many years. For example, an article in a November 2010 production titled Nutraceutical antioxidants as novel neuroprotective agent expands on the classes of “antioxidant” compounds that are neuroprotective and operate either via direct antioxidant action or via the keap1-Nrf2 pathway:

“A variety of antioxidant compounds derived from natural products (nutraceuticals) have demonstrated neuroprotective activity in either in vitro or in vivo models of neuronal cell death or neurodegeneration, respectively. These natural antioxidants fall into several distinct groups based on their chemical structures: (1) flavonoid polyphenols like epigallocatechin 3-gallate (EGCG) from green tea and quercetin from apples; (2) non-flavonoid polyphenols such as curcumin from tumeric and resveratrol from giant knotweed and grapes; (3) phenolic acids or phenolic diterpenes such as rosmarinic acid or carnosic acid, respectively, both from rosemary; and (4) organosulfur compounds including the isothiocyanate, L-sulforaphane, from broccoli and the thiosulfonate allicin, from garlic.

“All of these compounds are generally considered to be antioxidants.  They may be classified this way either because they directly scavenge free radicals or they indirectly increase endogenous cellular antioxidant defenses, for example, via activation of the nuclear factor erythroid-derived 2-related factor 2 (Nrf2) transcription factor pathway. Alternative mechanisms of action have also been suggested for the neuroprotective effects of these compounds such as modulation of signal transduction cascades or effects on gene expression. Here, we review the literature pertaining to these various classes of nutraceutical antioxidants and discuss their potential therapeutic value in neurodegenerative diseases.”

DIETARY FLAVONOIDS AS NRF2 ACTIVATORS

One of the ways dietary flavonoids work to confer their multiple health effects is via the keap1-Nrf2 pathway.  That is substances which are both themselves antioxidants and activators of the keap1-Nrf2 pathway produce significant results through keap1-Nrf2 and activating the body’s own antioxidant and defensive systems.

Flavonoids are a large family of polyphenolic compounds synthesized by plants. Many of the common dietary flavonoids are shown in Table 1 below along with their common food sources.

In addition to flavonoids many other plant based substances appear to produce health benefits through hormetic effects mediated by Nrf2.  The December 2011 publication Nutritional antioxidants and adaptive cell responses: an update reports: “Many plant antioxidants, intaken through the daily diet or plant-derived dietary supplements, have been shown able to prevent free radical-related diseases by counteracting cell oxidative stress. However, it is now considered that the in vivo beneficial effects of these phytochemicals are unlikely to be explained just by their antioxidant capability.

“Several plant antioxidants exhibit hormetic properties, by acting as ‘low-dose stressors’ that may prepare cells to resist more severe stress. In fact, low doses of these phytochemicals activate cell signaling pathways (being the most prominent examples the modulation of the Nrf2/Keap1 pathway, the NF-κB pathway and the Sirtuin-FOXO pathway) but high doses are cytotoxic.

“Herein we review the adaptive responses induced by the most known plant hormetic antioxidants, which are sulforaphane, resveratrol, curcumin, flavonoids, green tea catechins and diallylsulphides [in garlic], as well as the molecular mechanisms involved in such responses. Furthermore, this review outlines that the hormetic properties of these bioactive plant antioxidants might be successfully employed for realizing health-promoting dietary interventions especially in the field of neurodegenerative diseases and cancer.”

INTERESTING FACTS REGARDING NRF2 ACTIVATORS

1) An interesting fact is that Nrf2 is ubiquitously expressed with the highest concentrations (in descending order) in the kidney, muscle, lung, heart, liver, and brain. 

2) Another important fact is that the well-known nutrition supplement lipoic acid is a potent activator of Nrf2 and thus increases Gluthatione levels, which may explain its protective effect against diabetic co-morbidities. Additionally, the nutritional supplements tocotrienols (active forms of Vitamin E) and N-Acetyl-L-Cysteine (NAC) are also effective Nrf2 activators!

3) We have observed that the natural plant substances with the highest ORAC5.0 values appear to be among the most effective Nrf2 activators. For example, see the table below. In particular, note that Curcumin (98%), Grape Seed Extract, Green Tea Extract, and Reservatrol which are commonly used for their excellent Nrf2 activator effects are the most powerful in-vitro antioxidants . Please note that Ultimate Protector+ is over 100% more powerful as an antioxidant than the best single plant ingredient.

TABLE 2: ORAC5.0™ COMPARATIVE RESULTS

NEUROPROTECTION BY POLYPHENOL STIMULATION OF THE NRF2 / ARE PATHWAY 

Modulation of Nrf2/ARE pathway by food polyphenols: a nutritional neuroprotective strategy for cognitive and neurodegenerative disorders. (Oct. 2011)

ABSTRACT

In recent years, there has been a growing interest, supported by a large number of experimental and epidemiological studies, for the beneficial effects of some phenolic substances, contained in commonly used spices and herbs, in preventing various age-related pathologic conditions, ranging from cancer to neurodegenerative diseases. Although the exact mechanisms by which polyphenols promote these effects remain to be elucidated, several reports have shown their ability to stimulate a general xenobiotic response in the target cells, activating multiple defense genes.

Data from our and other laboratories have previously demonstrated that curcumin, the yellow pigment of curry, strongly induces heme-oxygenase-1 (HO-1) expression and activity in different brain cells via the activation of heterodimers of NF-E2-related factors 2 (Nrf2)/antioxidant responsive element (ARE) pathway. Many studies clearly demonstrate that activation of Nrf2 target genes, and particularly HO-1, in astrocytes and neurons is strongly protective against inflammation, oxidative damage, and cell death. In the central nervous system, the HO system has been reported to be very active, and its modulation seems to play a crucial role in the pathogenesis of neurodegenerative disorders.

Recent and unpublished data from our group revealed that low concentrations of epigallocatechin-3-gallate, the major green tea catechin, induces HO-1 by ARE/Nrf2 pathway in hippocampal neurons, and by this induction, it is able to protect neurons against different models of oxidative damages. Furthermore, we have demonstrated that other phenolics, such as caffeic acid phenethyl ester and ethyl ferulate, are also able to protect neurons via HO-1 induction. These studies identify a novel class of compounds that could be used for therapeutic purposes as preventive agents against cognitive decline.

The major green tea polyphenol, (-)-epigallocatechin-3-gallate, induces heme oxygenase in rat neurons and acts as an effective neuroprotective agent against oxidative stress. (Aug. 2009)

ABSTRACT

Oxidative stress induced by hyperglycemia is a key factor in the pathogenesis of diabetic complications, such as neuropathy. Recently, green tea catechins have received much attention, as they can facilitate a number of antioxidative mechanisms and improve glycemic control. The aim of this study was to investigate the cytoprotective effects of (-)-epigallocatechin-3-gallate (EGCG) against oxidative stress damage in a cell line of rat neurons. The role of heme oxygenase 1 (HO-1) induction by EGCG and the transcriptional mechanisms involved were also evaluated.

Immortalized rat neurons (H 19-7) were exposed to various concentrations of EGCG (10-200 microM). After treatments (6 or 24 hours), cells were harvested for the determination of heme oxygenase activity, mRNA levels, and protein expression. Nuclear levels of Nrf2, a transcriptional factor involved in HO-1 activation, were also measured. Neurons were pretreated for 12 hours with EGCG 50 microM or EGCG 50 microM + zinc protoporphyrin IX 10 microM and then exposed for 2 hours to 50 mmicro/mL glucose-oxidase before cell viability was determined.

In cultured neurons, elevated expression of HO-1 mRNA and protein were detected after 6 hours of incubation with 25-100 microM EGCG, and its induction relates with the activation of Nrf2. Interestingly, pre-incubation (12 hours) with EGCG 50 microM resulted in an enhanced cellular resistance to glucose oxidase-mediated oxidative damage; this cytoprotective effect was considerably attenuated by zinc protoporphyrin IX, an inhibitor of heme oxygenase activity.

In this study, we demonstrated that EGCG, the major green tea catechin, induced HO-1 expression in cultured neurons, possibly by activation of the transcription factor Nrf2, and by this mechanism was able to protect against oxidative stress-induced cell death.

The following review article abstract shows how natural products containing Nrf2 activator/antioxidant ingredients might be used to support health and anti-aging.