The Many Sides of Polyphenols

Polyphenols are enablers. These plant-based actives that are the force behind the health benefits of chocolate, wine, coffee and other consumer favorites. This wide class of antioxidants has enjoyed a growing body of research showing beneficial impacts on health issues such as obesity, diabetes, cancer, neurological conditions and cardiovascular disease (CVD). Polyphenols are increasingly used in dietary supplement and functional food and beverage formulation, but not without some challenges.

Polyphenols are the most abundant antioxidants in the diet, according to European researchers, who placed their probable total dietary intake as high as 1 gram per daythis is 10 times as high as vitamin C, and 100 times as high as vitamin E and carotenoid intakes.¹ Still, as modern diets move away from a foundation of whole plant foods to include more animal and processed foods, intake of bioavailable polyphenols may be suffering.

"In addition to macronutrients (proteins, fats and carbohydrates) and to the essential micronutrients (vitamins and mineral salts), recently, polyphenols have emerged as a major class of dietary ingredients that can positively affect human health, and their reduced intake in the western diet has already been connected to the increase in the onset of chronic degenerative diseases, cancer being the first and foremost," said Christian Artaria, marketing director and head of functional food, Indena SpA. "While more observational studies linking the intake of these compounds and the occurrence of certain pathologies form one side and mechanistic and controlled studies confirming their role in the substantiation of the effects are still needed, we can foresee a continuous growth of their use in western countries." He suggested currently elderly people feel more concerned about these issues, but there is a realistic potential for increased involvement in younger adults embracing polyphenols for a variety of health benefits.

Polyphenols include phenolic acids, flavonoids, stilbenes and lignans. Defined by a structure of hydroxyl groups on aromatic rings, polyphenols help defend host plants from ultraviolet (UV) radiation or from pests. On one hand, these defensive properties make polyphenols good candidates for use in protecting human health, but they can also pose challenges for use in product formulation.

Artaria said polyphenols can present taste, color and stability challenges. "Polyphenols are bitter, and this bitterness should be masked," he noted. These compounds also tend to be colorful, which can cause problems for food matrices, he added. They are also relatively unstable. "This is true in general, but in particular, when glycosides are attached to polyphenols, they can easily be hydrolyzed in water," he said. "Another problem may be the thermo-ability of polyphenols, too; at high temperatures, they can easily be degraded."

However, Artaria warned it is difficult to generalize about the characteristic challengestaste and color traits, as well as sensitivities to temperature and oxygenof such a broad class of compounds as polyphenols. "Depending on the formulation and the specificity of each ingredient, there are different guidelines to follow," he reminded formulators. "In general, the selection of low temperatures and dry processes is preferred. However, in some cases along with using these preferred conditions, it is important to protect the integrity of the polyphenols in processing by flooding equipment with nitrogen to prevent the ingredients from getting in contact with oxygen."

Matt Phillips, president and chief operating officer of Cyvex Nutrition, agreed polyphenols are bitter, and formulators need to find creative ways to mask the bitterness. "For example, our grape extract is used in a chewable application, and the bitterness of the grape is masked with a sweetener and grape flavor," he said. The best applications for polyphenols, he said, are beverages, tablets, capsules, gummies. "These applications lend themselves to masking better than other delivery mechanisms," he said. "New applications are easy-melt tablets, one-shot beverages and medical foods."

Alison Raban, a food technologist with BI Nutraceuticals, also focused on the taste and color of polyphenols. "Formulators should keep [taste] in mind when determining where the polyphenols are coming from (i.e. tea or fruit/vegetable) and how much to addwith lighter flavored products a high polyphenol level might add too much bitterness," she advised. "For beverages, tea powders, especially green tea powders, are a great go-to ingredient for polyphenols, but they are also a great ingredient for baked and snack foods. Fruit and vegetable powders and extracts are another good source for polyphenols if a tea ingredient seems out of place in a product." She further advised when using fruit- and vegetable-sourced polyphenols, especially anthocyanins from fruits such as grapes, blueberries, cranberries and other dark fruits, formulators should keep color in mind. "Some anthocyanins are used for their color more than polyphenol content so if working with a light colored food or beverage, the color of the ingredient might restrict use level."

Raban noted green tea polyphenols are an obvious addition to beverages, especially teas, but also work great in other food applications from cereals to snacks and chips, and even baked goods like breads and muffins. In addition to tea polyphenols, BI also offers polyphenols from fruit and vegetable sources as well as custom blends. "We find our customers are not only looking for polyphenol content but also a unique mix of different sources of polyphenols to help differentiate their product from others," she said. "This also gives the marketers of foods more options when creating advertising material."

Because of the array of different polyphenols, each with a unique set of characteristics and properties, available to formulators, dietary supplements have been the primary area of polyphenol use. Solid form supplements offer more easily controlled formulation compared to some of the complex functional food and beverage applications. However, formulators, scientists and developers have been rising to the challenges of using polyphenols in these more complex delivery forms. Scott Steil, president of Nutrabridge, said the most common delivery format for InSea2, a polyphenol weight management product derived from brown seaweed (from innoVactiv), is in capsules. However, the ingredient also has been used in powders, lemon ice tea drink mixdue to good effervescent properties, tablets, chewables and chocolates. "One of the key benefits of the product is that is it heat stable," Steil noted. "This dramatically increases the flexibility of applications that InSea2 can fit."

On the best applications for polyphenols, Roberto Crea, Ph.D., founder and CEO of CreAgri, reminded formulators that each family of plant polyphenols can be quite different in activity, bioavailability and mechanism of action. "Polyphenols are a very large family of natural compounds whose structure and bioavailability should not encourage generalizations," he advised. On olive polyphenols, and, specifically, hydroxytyrosol, Crea said the best applications are food and beverages, functional foods and dietary supplements. He explained the ingredient is water- and fat-compatible, which means it has broad applications. "Its water solubility makes it very suitable to liquid applications including beverages, but also salad dressing, juices, elixir, tea, dairy and other liquid mixes," he said.

The solubility challenges were highlighted by numerous experts. Scientists from the Lipid Research Laboratory at the Rappaport Family Institute for Research in the Medical Sciences and Rambam Medical Center, Haifa, Israel, reported the solubility of polyphenols in water is determined by their polarity.² "Flavanols, such as catechin or epicatechin, known to be present in grapes, are polar compounds, and therefore, are soluble in water," they explained. On the other hand, flavonols are insoluble in water and are usually found in foods in their glycosylated form. Speaking about grape polyphenols, they continued, "Thus, the flavonols present in grapes are probably present in the glycosylated form, particularly in view of the high concentration of glucose in the grape dry powder, and the glycosylation of the polyphenols increases their solubility in water." They said the same is true for the stilbene resveratrol.

The solubility of a given polyhenol is an obvious defining characteristic for beverage makers. Jeremy Bartos, Ph.D., ingredient product manager for Chromadex, which offers the polyphenol pterostilbene as PteroPure®, said since pterostilbene is lipophilic (fat-soluble), beverage customers have been asking for a water-soluble version of pterostilbene. "We are currently working with partners to create a water-soluble version," he noted, advising in the interim, those interested in using pTeroPure in a beverage are including it in premixes and drink powders. "With the small dose required for clinical efficacy, even if pterostilbene is not suspended in liquid, it will not be an issue with palatability or with intake."

Food and beverage formulations have a longer timeline than supplements, but the market should see a significant uptake in these products in first quarter 2013 and beyond, according to Bartos. He said skin care is another area that will see significant growth in the next 12 to 18 months. "Because of its lipophilic nature, pterostilbene works well in oil-based lotions and creams and also absorbs nicely and directly into the skin," he explained. "Expect to see an uptick in the cosmeceutical and even sun care industries in the next few years." Animal health industry, especially in the equine market, is another emerging channel.

Bartos said pterostilbene is already available in capsules, tablets, drink powders, granola bars, cookies, popcorn and fast melts, but such lipophilic polyphenols are ideal for softgel formulation, a delivery form he is surprised hasn't been utilized for pterostilbene. "And its heart-health benefits makes it a perfect partner for a fish oil formulation," he said. "With the efficacy results of the first human clinical trial on pterostilbene slated for sometime in September or October, I wouldnt be surprised to see this come to fruition sooner rather than later."

Another transformation in formulation of polyphenols is the targeting of specific benefits and related mechanisms of action. Polyphenols have primarily been touted for their antioxidant benefits, relative to the extensive body of literature showing a oxidative stress plays a part in age-related disease. Researchers have long thought polyphenols and antioxidants protect body cells from free radical damage, but this simplified theory may not tell the whole story. In fact, researchers have found both anti- and pro-oxidant properties have been found in various polyphenols, and they now speculate polyphenols may act on receptors and enzymes.³ For instance, soy isoflavones interact with estrogen receptors and can thereby affect endocrine function.

Steil said brown seaweed polyphenols inhibit both alpha-amylase and alpha-glucosidase enzymes at a high potency level. "We recently completed another round of new human studies that further document InSea2s ability to significantly reduce blood glucose levels by 48 percent and insulin levels by 12 percent, and increase insulin sensitivity by 8 percent versus placebo," he said, noting the study was recently published.⁴

Pterostilbene activates peroxisome proliferator receptor (PPAR) alpha, a protein which, when activated, acts to inhibit the bodys production of native cholesterol and triglycerides. For this reason, a good formulation partner could be phytosterols, which are the plants version of cholesterol. Bartos explained phytosterols are absorbed in the digestive system in the same manner as ingested cholesterol and thus act to block the absorption of ingested cholesterol by the body. "The two ingredients together are synergistic because one works on ingested cholesterol (phytosterols) and one works on native cholesterol (pterostilbene)," he suggested, noting the key to synergistic formulation with polyphenols is finding ingerdients with related health benefits, but different mechanistic pathways. "Similar cases can be made with pterostilbene and fish oil for triglyceride lowering, with Ginkgo biloba for cognitive function, and with cinnamon for maintaining blood sugar levels," he said. Resveratrol and quercetin are other polyphenols that could work synergistically with pterostilbene.

While polyphenols can work toward a number of health benefits in humans, they must first be absorbed sufficiently. Researchers have noted the most common polyphenols in the human diet are not necessarily the most active in the body, because they are poorly absorbed, highly metabolized or rapidly eliminated by the digestive system. This makes bioavailability a key issue for formulators dealing with polyphenols.

While aglycones can be absorbed in the small intestine, the common dietary formsglycosides, esters and polymersrequire hydrolysis by intestinal enzymes or colonic microflora for absorption. However, microflora can reduce absorption efficiency. Absorption involves methylation, glucuronidation and sulfation in the intestines and liver. Flavonoids, except for flavanols, are in glycosylated form. There is some evidence flavonoids such as diadzein and quercetin can be absorbed at the gastric level, but the glycosides can not.⁵ The glycosides resist hydrolysis in the stomach, leaving them intact in the intestines. In these cases, absorption can be dependent on accompanying compounds. For instance, quercetin is better absorbed from foods rich in glucosides, compared to in foods rich in glycosides.

Proanthocyanidins and anthocyanins may be poorly absorbed due to their size and high molecular weight. In fact, oligomers larger than trimers in their native forms may not be absorbed in the small intestine, but may require hydrolysis, although this also is no guarantee of absorption.⁶ Only dimers and trimers of flavanols cross the intestinal epithelium.⁷ Researchers have concluded intakes of monomeric flavonols, flavones and flavanols are relatively low, with plasma concentrations rarely exceeding 1 umol/L due to poor absoprtion and increased elimination. Flavanones and isoflavones might offer the best bioavailability, with plasma concentration often reaching 5 umol/L.

On bioavailability, Bartos further noted two "gates" can impeded polyphenol bioavailability. First, the greater number of hydroxyl groups a polyphenol has, the greater the chance the liver will tag the polyphenol for elimination. Further, uptake into body cells is limited by the cell's phospholipid bilayer shell. Lipophilic (oil soluble) compounds are more easily absorbed into the cell than are hydrophilic (water soluble) compoundspolyphenols with free hydroxyl groups are more water soluble, and those with free methoxy groups are more oil soluble. For example, resveratrol has three hydroxyl groups, giving it great antioxidant potential, but making it more susceptible to elimination directed by the liver. Not being lipophilic, resveratrol faces a tougher time getting through the bilayer and into the cell. Conversely, a compound with methoxy groups will offer great bioavailability, but decreased antioxidant potential. Pterostilbene has one hydroxyl and two methoxy groups, giving it good bioavailability and antioxidant potential.

Artaria stressed the importance of a balance of both hydrophilic and lipophilic properties for bioavailability. As such, Indena utilizes highly absorbable phospholipids, such as phosphatidylcholine (PC), as carriers for water-soluble polyphenolics. The company leveraged this technology to create its Phytosome® line of polyphenols with improved bioavailability. The line includes polyphenols from plants such as boswellia, Ginkgo biloba, green tea, Panax ginseng, curcumin, grape seed milk thistle and hawthorn flower.

Formulators will improve their chances of a successful and efficacious product by considering bioavailability along with all the other influential properties of polyphenols and the current status of researched benefits. "Todays formulators are looking for targeted efficacy and claims support when developing new products," Steil said, noting the number one question is: What messages can the product support? "After a clear functional benefit can be defined, additional characteristics include dose per serving, water solubility, organoleptic properties, heat stability, extraction methods and supply sustainability."

Crea had a similar list of formulation considerations. He emphasized proven safety and efficacy, a desirable cost-benefit proposition, assurance of a reputable materials source, possibility of added benefits (i.e. proprietary formulation) and the use of organic, when possible.

Polyphenols can vary greatly in terms of structure and properties, making formulation with this class of compounds dependent on consideration of each polyphenol on its own merits and challenges. Overall, the group of polyphenols offer much promise to human health via antioxidant or other mechanism, including impact on receptors and enzymes. The portrait of polyphenols cannot be painted with one brush or on one canvas. It has many faces and many stories to tell, as scientists are still learning more details about how these vibrant and ubiquitous compounds influence health and how formulators can harness their potential.

References Listed on the next page.

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References:

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3. IBID Scalbert A.

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5. Crespy V et al. "Quercetin, but not its glycosides, is absorbed from the rat stomach." J Agric Food Chem. 2002;50:618-21.

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7. Deprez S et al. "Transport of proanthocyanidin dimer, trimer and polymer across monolayers of human intestinal epithelial." Antiox Redox Signal. 2001;3:957-67.