Last week, when I was looking up references for wintergreen, I got a little sidetracked down polyphenol lane. I decided to tuck away these nuggets of information for the future and expand on my findings in another blog for my fellow essential oil groupies and BreakFree readers.

Welcome to the future…




I mentioned previously how I believe that essential oils are an overlooked source of polyphenols (phenolic acids). (1-5) These compounds and other secondary metabolites in them can serve to assist with modulating our amazing microbiome and our health in many beneficial ways. (6-7) Genuine essential oils may actually provide a synergistic and amplifying effect of dietary intake of polyphenols due to the fact that they can penetrate through the skin and directly enter circulation. (8) Why is this important?

The latest human intervention trials are demonstrating that action of polyphenolics in foods probably depends on the metabolic breakdown of them by our microbiota in the colon which gives rise to small phenolic and aromatic catabolites. These breakdown products are then absorbed into the circulatory system. (9-11) Unfortunately, most people have some messed up microbiomes; therefore, topical applications of essential oils may provide a means to assist with modulating the microbiome while the potent health promoting effects of polyphenols takes effects. The following excerpt from a 2013 review in Antioxidants and Redox Signaling explains this complex bioactivity of polyphenolics after ingestion:

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-uM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.(11)

Furthermore, this same review summarizes the importance of studying these components and why we would want their beneficial effects:

While not essential for the successful growth and development of most plants, flavonoids and related phenolic compounds* can occur in high concentrations in some species and are referred to as secondary metabolites. They are structurally diverse with in excess of 8000 structures having been reported (447), and many are found in only a limited number of species. In planta, they have various functions, including protecting plants from herbivores and microbial infection, as attractants for pollinators and seed-dispersing animals, as allelopathic agents, UV protectants, and signal molecules in the formation of nitrogen-fixing root nodules (95, 218).

The role of flavonoids and related compounds, as components responsible, in part, for the protective effects of a fruit- and vegetable-rich diet has become an increasingly important area of human nutrition research. Unlike the traditional vitamins, they are not essential for short-term well being, but there is increasing evidence that modest long-term intakes can have favorable effects on the incidence of cancers and chronic diseases, including cardiovascular disease (CVD), type II diabetes, and impaired cognitive function, which are occurring with increasing frequency in Western populations (433). This review will summarize the different groups of compounds that are involved, their fate in the body after ingestion as they pass through the gastrointestinal tract (GIT) and are absorbed into the circulatory system, the evidence of their protective impact on human health, and the possible mechanisms of action through which their metabolites may exert such effects. (11)


A Classification of phenolic compounds

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Before I go further into discussion on the power of phenolic compounds, I wanted to give those who are fellow geeks some simple biochemistry of what they are. Phenolics are a diverse group of  compounds containing at least one aromatic ring with one or more hydroxyl groups attached. They are further classified as flavonoids and nonflavonoids. Below is a quick overview:

A. Flavonoids contain the following subclasses:

  1. Flavonols, such as kaempferol, quercetin, isorhamnetin, and myricetin
  2. Flavones, such as apigenin, luteolin, wogonin, and baicalein, are similar structurally to flavonols, except they lack oxygenation at C-3
  3. Isoflavones, which are found almost exclusively in leguminous plants
  4. Flavanones, such as naringenin and hesperetin
  5. Anthocyanidins, with the most common anthocyanidin aglycones being pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin
  6. Flavan-3-ols, the most complex subclass of flavonoids, ranging from the simple monomers to the oligomeric and polymeric proanthocyanidins, which are also known as condensed tannins
  7. Dihydrochalcones, a minor group of flavonoids, of limited dietary significance

B. Nonflavonoids, among the nonflavonoids of dietary significance are the C6–C1 phenolic acids including gallic acid and ellagic acid-based ellagitannins (11)


More On Phenolic Power

Now that we know some biochemistry, or decided to skim over it, let’s look more into some research on these powerful constituents in plants. These compounds from medicinal herbs and dietary plants have been studied extensively in the literature for their health-promoting properties.


PageLines- forms-icon.png1. Modulating Cellular Pathways

Phenolic compounds have been studied for their role in modulating the immune system, influencing cellular differentiation and signaling pathways, antioxidant effects, and cardiovascular health. According to a 2010 article in Nutrition and Cancer:

Natural phenolic compounds play an important role in cancer prevention and treatment. Phenolic compounds from medicinal herbs and dietary plants include phenolic acids, flavonoids, tannins, stilbenes, curcuminoids, coumarins, lignans, quinones, and others. Various bioactivities of phenolic compounds are responsible for their chemopreventive properties (e.g., antioxidant, anticarcinogenic, or antimutagenic and anti-inflammatory effects) and also contribute to their inducing apoptosis by arresting cell cycle, regulating carcinogen metabolism and ontogenesis expression, inhibiting DNA binding and cell adhesion, migration, proliferation or differentiation, and blocking signaling pathways. This review covers the most recent literature to summarize structural categories and molecular anticancer mechanisms of phenolic compounds from medicinal herbs and dietary plants. (12)


PageLines- forms-icon.png2. Modulating Inflammation

This abstract reviews how phenolic compounds also modulate inflammatory pathways:

Spices, like vegetables, fruit, and medicinal herbs, are known to possess a variety of antioxidant effects and other biological activities. Phenolic compounds in these plant materials are closely associated with their antioxidant activity, which is mainly due to their redox properties and their capacity to block the production of reactive oxygen species. More recently, their ability to interfere with signal transduction pathways involving various transcription factors, protein kinases, phosphatases, and other metabolic enzymes has also been demonstrated. Many of the spice-derived compounds which are potent antioxidants are of great interest to biologists and clinicians because they may help protect the human body against oxidative stress and inflammatory processes. It is important to study the bioactive compounds that can modulate target functions related to defence against oxidative stress, and that might be used to achieve health benefits individually. In the present review, an attempt has been made to summarize the most current scientific evidence about the in vitro and in vivo effects of the bioactive compounds derived from herbs and spices, focused on anti-inflammatory and antioxidant effects, in order to provide science-based evidence for the traditional uses and develop either functional foods or nutraceuticals.(13)

PageLines- forms-icon.png3. Belly Soother Properties

One review article examined the role of phenolic compounds in preventing gastric ulcers in vitro and in vivo and concluded:

Peptic ulcer is the most common gastrointestinal tract (GIT) disorder in clinical practice, which affects approximately 5-10% of the people during their life. The use of herbal drugs for the prevention and treatment of various diseases is constantly developing throughout the world. This is particularly true with regard to phenolic compounds that probably constitute the largest group of plants secondary metabolites. Phenolic compounds have attracted special attention due to their health-promoting characteristics. In the past ten years a large number of the studies have been carried out on the effects of phenolic compounds on human health. Many studies have been carried out that strongly support the contribution of polyphenols to the prevention of cardiovascular diseases, cancer, osteoporosis, neurodegenerative diseases, and diabetes mellitus, and suggest a role in the prevention of peptic ulcer. Polyphenols display a number of pharmacological properties in the GIT area, acting as antisecretory, cytoprotective, and antioxidant agents. The antioxidant properties of phenolic compounds have been widely studied, but it has become clear that their mechanisms of action go beyond the modulation of oxidative stress. Various polyphenolic compounds have been reported for their anti-ulcerogenic activity with a good level of gastric protection. Besides their action as gastroprotective, these phenolic compounds can be an alternative for the treatment of gastric ulcers. Therefore, considering the important role of polyphenolic compounds in the prevention or reduction of gastric lesions induced by different ulcerogenic agents, in this review, we have summarized the literature on some potent antiulcer plants, such as, Oroxylum indicum, Zingiber officinale, Olea europaea L., Foeniculum vulgare, Alchornea glandulosa, Tephrosia purpurea, and so on, containing phenolic compounds, namely, baicalein, cinnamic acid, oleuropein, rutin, quercetin, and tephrosin, respectively, as active constituents. (14)


Bugs 4. May Inhibit A Nasty Parasite

This in vitro study demonstrated how several phenolic-rich essential oils inhibited the growth of Giardia but didn’t have cytotoxic effects in mammalian cells:

The present work evaluates the anti-Giardia activity of phenolic-rich essential oils obtained from Thymbra capitata, Origanum virens, Thymus zygis subsp. sylvestris chemotype thymol, and Lippia graveolens aromatic plants. The effects were evaluated on parasite growth, cell viability adherence, and morphology. The tested essential oils inhibited the growth of Giardia lamblia. T. capitata essential oil is the most active followed by O. virens, T. zygis subsp. sylvestris, and L. graveolens oils. The tested essential oils at IC50 (71-257) microg/ml inhibited parasite adherence (p < 0.001) since the first hour of incubation and were able to kill almost 50% of the parasites population in a time-dependent manner. The main ultrastructural alterations promoted by essential oils were deformations in typical trophozoite appearance, often roundly shape, irregular dorsal and ventral surface, presence of membrane blebs, electrodense precipitates in cytoplasm and nuclei, and internalization of flagella and ventral disc. Our data suggest that essential oils induced cell death probably by processes associated to the loss of osmoregulation caused by plasmatic membrane alterations. Experiments revealed that the essential oils did not present cytotoxic effects in mammalian cells. In conclusion, T. capitata, O. virens, T. zygis subsp. sylvestris chemotype thymol, and L. graveolens essential oils have antigiardial activity in vitro and seem to have potential for the treatment of the parasitic disease caused by the protozoan G. lamblia. (15) 



Essential oils are an amazing way to get the benefits of polyphenols that provide a wide array of health benefits and make for happy gut bugs.

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Disclaimer: This information is applicable ONLY for therapeutic, Grade A essential oils. This information DOES NOT apply to essential oils that have not been AFNOR and ISO standardized. There is no quality control in the United States and oils labeled as “100% pure” need only contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin. This information is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. These studies are not specific for any company or manufacture of herbal, supplement, or essential oil products. Please check the study for references.



(1)Plant phenylpropanoids as emerging anti-inflammatory agents.Mini Rev Med Chem. 2011 Sep;11(10):823-35.

(2) Lemberkovics, &.E.a.c.u.t.e.;., Petri, G., Nguyen, H. and Máthé, I. 1996. Relationships Between Essential Oil and Flavonoid Biosynthesis in Sweat Basil. Acta Hort. (ISHS) 426:647-656.

(3) Yoshiko Fukuchi, Masanori Hiramitsu, Miki Okada, Sanae Hayashi, Yuka Nabeno, Toshihiko Osawa, Michitaka Naito. Lemon Polyphenols Suppress Diet-induced Obesity by Up-Regulation of mRNA Levels of the Enzymes Involved in beta-Oxidation in Mouse White Adipose Tissue. J Clin Biochem Nutr. 2008 Nov;43(3):201-9. Epub 2008 Oct 31. PMID: 19015756

(4) Yoshiaki Miyake, Mika Mochizuki, Miki Okada, Masanori Hiramitsu, Yasujiro Morimitsu, Toshihiko Osawa. Isolation of antioxidative phenolic glucosides from lemon juice and their suppressive effect on the expression of blood adhesion molecules. Biosci Biotechnol Biochem. 2007 Aug;71(8):1911-9. Epub 2007 Aug 7. PMID: 17690486

(5) Essential oils, phenolics, and antioxidant activities of different parts of cumin (Cuminum cyminum L.). J Agric Food Chem. 2010 Oct 13;58(19):10410-8. doi: 10.1021/jf102248j.

(6) Jacques PF, Cassidy A, Rogers G, Peterson JJ, Meigs JB, Dwyer JT. Higher Dietary Flavonol Intake Is Associated with Lower Incidence of Type 2 Diabetes. Journal of Nutrition 2013 September 143(9):1474-80.

(7) Wang X, Ouyang YY, Liu J, Zhao G. Flavonoid intake and risk of CVD: a systematic review and meta-analysis of prospective cohort studies. British Journal of Nutrition 2013 August 16:1-11. Available at:

(8) Essential oils and their constituents as skin penetration enhancer for transdermal drug delivery: a review. J Pharm Pharmacol. 2014 Dec 31. doi: 10.1111/jphp.12334. [Epub ahead of print]

(9) Metabolites Are Key to Understanding Health Effects of Wine Polyphenolics. J. Nutr. September 2009 vol. 139 no. 9 1824S-1831S.

(10) The mechanisms underlying these processes are discussed. Dietary phenolics: chemistry, bioavailability and effects on health. Nat Prod Rep. 2009 Aug;26(8):1001-43. doi: 10.1039/b802662a. Epub 2009 May 13.

(11) Del Rio D, Rodriguez-Mateos A, Spencer JPE, Tognolini M, Borges G, Crozier A. Dietary (Poly)phenolics in Human Health: Structures, Bioavailability, and Evidence of Protective Effects Against Chronic Diseases. Antioxidants & Redox Signaling .2013;18(14):1818-1892. doi:10.1089/ars.2012.4581.

(12) Natural phenolic compounds from medicinal herbs and dietary plants: potential use for cancer prevention. Nutr Cancer. 2010;62(1):1-20. doi: 10.1080/01635580903191585.

(13) Recent advances in biologically active compounds in herbs and spices: a review of the most effective antioxidant and anti-inflammatory active principles. Crit Rev Food Sci Nutr. 2013;53(9):943-53. doi: 10.1080/10408398.2011.574802.

(14) Sumbul S, Ahmad MA, Mohd. A, Mohd. A. Role of phenolic compounds in peptic ulcer: An overview. Journal of Pharmacy and Bioallied Sciences 2011;3(3):361-367. doi:10.4103/0975-7406.84437.

(15) Anti-Giardia activity of phenolic-rich essential oils: effects of Thymbra capitata, Origanum virens, Thymus zygis subsp. sylvestris, and Lippia graveolens on trophozoites growth, viability, adherence, and ultrastructure. Parasitol Res. 2010 Apr;106(5):1205-15. doi: 10.1007/s00436-010-1800-7. Epub 2010 Mar 9.

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