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Grape Chemistry

Health-Promoting Plant Nutrients

Grape Chemistry: Health-Promoting Plant Nutrients

The plant nutrients within the Concord grape include polyphenols, such as anthocyanins, catechin, epicatechin, and quercetin, which are flavonoids1-5 and potentially resveratrol, which is a stilbene.6

In a study by Munoz-Espada, Concord grapes were abundant in anthocyanins, which, in vitro, also displayed antioxidant activity.4 Furthermore, Dr. Gu and colleagues estimated that Americans’ third highest source of proanthocyanidins were grapes. Grapes and grape juice were shown to contribute nearly 18% of the total ~ 58 milligrams proanthocyanidin/person/day (> 2 years old).7 In fact, purple grape juice had the highest content of proanthocyanidins of all beverages (including red wine and fruit juices), at 124 milligrams per 8 fluid ounces.8


Research continues to show these plant-based nutrients (phyto = plant) may have health benefits, and they are being actively investigated in the scientific community. Foods filled with phytonutrients include fruits (like Concord and Niagara grapes), vegetables, legumes, whole grains, nuts, and tea. Polyphenols, including flavonoids (e.g., flavonols, flavanols, flavanones, flavones, isoflavones, anthocyanins), phenolic acids, and stilbenes, comprise one group of phytonutrients.


This sub-group of phytonutrients is found in a variety of foods, including grapes and grape juice, onions, tea, red wine, blueberries, and certain nuts. They are often concentrated in the skins of fruits, and act as a protector from pathogens, parasites, and predators – in addition to contributing to the flavor and color of fruits and vegetables. Research is currently investigating whether these plant-based nutrients can also protect the health of humans.


These are naturally occurring compounds that comprise the largest and most studied sub-group of polyphenols. This group also includes the majority of phytonutrients found in the skins and seeds of Concord and Niagara grapes. There are thousands of different flavonoids found in nature, and fruits, vegetables, and plant-derived beverages (e.g., wine, grape juice, tea) contain many different types. Several of these biologically active compounds help to protect the plant from disease and damage and they are being actively studied to determine their potential role in human health. Sub-classes of flavonoids include flavonols, like quercetin, flavanols, like proanthocyanidins, and anthocyanins.


A major sub-class of flavonoids, they are typically found glycosylated (linked to a sugar) in nature and they are responsible for the red, purple or blue color of many fruits and flowers.

Catechin and Epicatechin

Common flavonoids found in beverages, these two related compounds are flavanols (or flavan-3-ols) a sub-class of flavonoids. They are the building blocks of proanthocyanidins. Teas, Concord and Niagara grapes, wine, apple juice, cocoa, and select legumes contain abundant quantities of these phytonutrients.


A common flavonol found in fruits, this is not to be confused with flavanol, in the human diet. This flavonoid can be found in fruits, vegetables, leaves, and grains.


This natural compound is a protector of plants that is sometimes found in the skins of deep-purple Concord grapes.6 This phytonutrient falls under the polyphenol sub-group of stilbenes.6 Optimal conditions for development of this phytonutrient include a cool and wet climate, without excessive sunshine; thus, the resveratrol content varies by grape cultivar, geographic location, and exposure to fungal infections.9 In early laboratory studies, this phytonutrient shows promise in supporting certain aspects of health, including cardioprotective effects and promoting immune health.10-12

For more information on the research behind Concord grapes and health,
visit Concord Grapes and Health.


  1. Fitzpatrick DF, Bing B, Maggi DA, Fleming RC, O'Malley RM. Vasodilating procyanidins derived from grape seeds. Ann N Y Acad Sci. 2002. 957:78-89.
  2. Freedman JE, Parker C, 3rd, Li L, Perlman JA, Frei B, Ivanov V, Deak LR, Iafrati MD and Folts JD. Select flavonoids and whole juice from purple grapes inhibit platelet function and enhance nitric oxide release. Circulation. 2001. 103(23):2792-2798.
  3. Mullen W, Marks SC, and Crozier A. Evaluation of Phenolic Compounds in Commercial Fruit Juices and Fruit Drinks. J Agric Food Chem. 2007. 55(8):3148–3157.
  4. Munoz-Espada AC, Wood KV, Bordelon B and Watkins BA. Anthocyanin quantification and radical scavenging capacity of Concord, Norton, and Marechal Foch grapes and wines. J Agric Food Chem. 2004. 52(22):6779-6786.
  5. Singletary KW, Stansbury MJ, Giusti M, van Breemen RB, Wallig M and Rimando A. Inhibition of Rat Mammary Tumorigenesis by Concord Grape Juice Constituents. J Agric Food Chem. 2003. 51(25):7280–7286.
  6. Wang Y, Catana F, Yang Y, Roderick R and van Breemen RB. An LC-MS method for analyzing total resveratrol in grape juice, cranberry juice, and in wine. J Agric Food Chem. 2002. 50(3):431-435.
  7. Gu L, Kelm MA, Hammerstone JF, Beecher G, Holden J, Haytowitz D, Gebhardt S, and Prior RL. Concentrations of proanthocyanidins in common foods and estimations of normal consumption. J Nutr. 2004. 134(3):613-617.
  8. U.S. Department of Agriculture. USDA Database for the Proanthocyanidin Content of Selected Foods. 2004. Accessed October 13, 2010. The database reports proanthocyanidins per 100 grams, for this comparison the values have been converted to an 8 oz standard serving size.
  9. Fremont L. Biological effects of resveratrol. Life Sci. 2000. 66(8):663-673.
  10. Leifert WR, Abeywardena MY. Cardioprotective actions of grape polyphenols. Nutr Res. 2008. 28(11):729-737.
  11. Udenigwe CC, Ramprasath VR, Aluko RE and Jones PJ. Potential of resveratrol in anticancer and anti-inflammatory therapy. Nutr Rev. 2008. 66(8):445-454.
  12. Falchetti R, Fuggetta MP, Lanzilli G, Tricarico M and Ravagnan G. Effects of resveratrol on human immune cell function. Life Sci. 2001. 70(1):81-96.
Eating a balanced diet rich in a variety of fruits and vegetables is important for maintaining overall health. Delicious Concord grapes and 100% grape juice are part of a nutritious diet, but they should not be used to treat health problems. If you are worried about your health or are faced with a medical concern, be sure to consult with your doctor.

Guide to Navigating Research Studies

The definition of scientific research is performing a methodical study in order to prove a theory or answer a question. The following is a brief overview of different types of research used in health and nutrition exploration 1:

Case-Control Study
Clinical Study
Cohort Study
Cross-Sectional Study
Observational Study
Pilot Study
Preclinical or Laboratory Studies
Randomized Controlled Trials


1. Hulley SB, Cummings SR, Browner WS, Grady D, Hearst N, Newman TB. Designing Clinical Research: An Epidemiologic Approach. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

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An observational study, usually a retrospective study (a study that looks backward in time) that compares two groups of people: 1) those with the specific condition (e.g., disease) being studied (cases) and, 2) a similar group of people without that condition (controls). Researchers compare these two groups of people and important characteristics, such as certain lifestyle choices, to determine what factors may be associated with the condition under investigation.

A type of study that often includes patients with specific health conditions who could benefit from receiving a new treatment. These studies can also be performed in healthy subjects. The end goal of a clinical study (also called clinical research or clinical trial) is to determine effectiveness and safety of a health intervention in humans.

An observational study, usually prospective (looking forward), that follows a group of similar people over time. The goal is to determine which factors and exposures affect the development of a specific outcome or health condition (e.g., disease) during the study’s time period.

A type of observational study, often given as a survey, that examines a group of subjects during a single occasion, or over a very short period of time. This type of study aims to describe the relationship between health-related conditions (e.g., metabolic syndrome, hypertension) and other factors that exist in the general population (e.g., dietary intake, physical activity levels), during a particular time period.

A type of study in which researchers simply observe subjects and measure the associations between certain characteristics (e.g., fruit/vegetable intake) and specific outcomes (e.g., obesity). Examples of observational studies include case-control studies, cross-sectional studies, and cohort studies. While these studies gather important information, they cannot prove that a specific treatment or factor affects health.

A small scale, preliminary study that is conducted to determine the potential for a larger study.

A stage of research that often occurs prior to trials involving humans. This type of research can help determine mechanisms of action of a treatment, or how the treatment is causing the effect, as well as help ensure the safety of treatment in subsequent human trials.

In vitro
Testing performed in a controlled environment, such as a test tube or a Petri dish, instead of living organisms. In vitro literally means "within the glass" in Latin.

Ex vivo
These experiments are performed on tissue (e.g., animal or human cells) taking place outside of the organism, such as in a laboratory setting. In Latin, this means "out of the living."

In vivo
These tests are done on whole, living organisms. Technically, animal and human testing are two forms of in vivo research, which means "within the living." These experiments may be performed outside of a laboratory setting.

A study designed to provide the most credible information about the cause and effects of treatment. These types of studies are recognized as unbiased because they involve the random assignment of treatments to subjects being studied.

The tendency throughout any stage of research to generate findings that may not reflect "true values." In clinical trials, researchers try to avoid many kinds of bias, including selection by randomizing subjects, measurement by creating placebos and performing blind trials, and confounding by carefully designing the study and analyzing the findings.

Study in which subjects do not know whether they receive the treatment or the placebo, which assists in prevention of bias. Double-blinded studies are a higher level of scientific rigor because neither the participants nor the investigators know who is receiving the treatment or the placebo. A double-blind crossover study means each participant undergoes both the treatment and control scenario, typically with a wash-out period in between.

Study that allows researchers to isolate the effect size of the treatment by comparing a group given a simulated treatment (e.g., grape flavored drink) to those with the real treatment (e.g., Concord grape juice), which reduces measurement bias. The placebo should match as closely as possible to the treatment without containing the active ingredients.

Study involving participants who are randomly assigned to either the treatment or the placebo group, reducing selection bias.