Grapes, renowned for their diverse phytochemical composition, have long been recognized for their health-promoting properties. This comprehensive review aims to synthesize the current research on grapes, with a particular emphasis on their role in disease prevention and health enhancement through bioactive compounds.
A meticulous review of peer-reviewed studies, including in vitro, in vivo, and clinical investigations, was conducted to elucidate the relationship between grape consumption and health outcomes. The review highlights the positive association of grape intake with a decreased risk of chronic diseases such as cardiovascular disease, type 2 diabetes, and certain cancers. Bioactive components like resveratrol are emphasized for their neuroprotective and antioxidative capabilities. Additionally, the review explores emerging research on the impact of grapes on gut microbiota and its implications for metabolic health and immune function.
This updated review underscores the importance of future research to fully leverage and understand the therapeutic potential of grape-derived compounds, aiming to refine dietary guidelines and functional food formulations. Further translational studies are expected to clarify the specific bioactive interactions and their impacts on health.
Nutritional Composition of Grapes
Grapes (Vitis spp.), cultivated across various climatic zones worldwide, present a rich diversity in species and hybrids. From the classic European Vitis vinifera to American varieties like Vitis labrusca and innovative hybrids, each brings unique qualities and adapts differently to environmental conditions, significantly enriching the global viticulture landscape.
Grapes are a repository of a multitude of bioactive compounds, including phenolic acids, flavonoids, stilbenes, and lignans, which contribute to their health-promoting properties. These compounds can be systematically classified into several categories:
- Phenolic Acids: Comprising hydroxybenzoic and hydroxycinnamic acids, these compounds are foundational to the antioxidant capacity of grapes.
- Flavonoids: This diverse group includes flavonols (such as quercetin and kaempferol), flavan-3-ols (catechins and proanthocyanidins), anthocyanins, and flavanones, renowned for their extensive health benefits including antioxidant, anti-inflammatory, and cardioprotective effects.
- Stilbenes: Resveratrol is the most notable stilbene in grapes, recognised for its neuroprotective and antioxidative properties.
- Lignans: Present in smaller quantities, lignans contribute to the overall antioxidant profile of grapes.
The extraction of these bioactive compounds from grapes is a pivotal step in utilizing these phytochemicals for health benefits. Conventional extraction methods have relied on solvent extraction techniques, while recent advancements have led to the development of novel extraction methods, such as Supercritical Fluid Extraction (SFE), Ultrasonic-assisted extraction (UAE), Enzyme-assisted extraction (EAE), and Pulsed Electric Field (PEF) extraction, that are more efficient, selective, and environmentally friendly.
Cardiovascular Health Benefits
Grapes contain a plethora of phenolic compounds, which are central to the fruit’s antioxidant, anti-inflammatory, and cardioprotective effects. These phenolics exist in various forms, including free phenolics, esterified phenolics, insoluble-bound phenolics, and non-extractable polyphenols (NEPPs), each with unique properties affecting their bioavailability and biological activity.
Free phenolics, readily available in the fruit matrix, are known for their immediate bioactivity. These compounds, including flavonoids and phenolic acids, exhibit potent antioxidant properties. Their direct interaction with cellular targets provides immediate health benefits, such as reducing oxidative stress and modulating inflammatory pathways.
Esterified phenolics, formed by the linkage of phenolic acids to sugars or alcohols, exhibit enhanced stability and solubility. This form contributes to the gradual release of phenolics in the gut, potentially offering sustained antioxidant activity.
Insoluble-bound phenolics, tethered to cell wall components, are released during digestion or food processing. These compounds, often overlooked in conventional extraction methods, contribute to long-term health benefits, particularly in gut health and chronic disease prevention, as the microbial fermentation of these bound phenolics in the colon produces metabolites with systemic health benefits.
NEPPs, a significant fraction of dietary polyphenols, are not absorbed in the upper gastrointestinal tract but are metabolized by the gut microbiota. This process yields a range of metabolites with potential health-promoting properties, highlighting the important role of the gut microbiome in unlocking the health benefits of grape phenolics.
The diverse forms of phenolic compounds in grapes hold significant potential for enhancing health through various mechanisms. Free phenolics are ideal for immediate effects, esterified phenolics for sustained release, and insoluble-bound phenolics for long-term benefits, particularly impacting gut health and chronic disease mitigation. The strategic extraction and formulation of these phenolics can lead to innovative health products tailored to specific health outcomes, leveraging the rich biodiversity of grape varieties.
Metabolic Health Advantages
Grape-derived polyphenols, particularly those found in wine and juice by-products such as grape pomace, have garnered attention for their potential to modulate blood glucose and improve insulin sensitivity. The antidiabetic efficacy of these compounds is partly attributed to their interaction with various proteins and enzymes linked to glucose metabolism.
In vitro studies focusing on grape-derived polyphenols such as resveratrol, quercetin, rutin, caffeic acid, and gallic acid have elucidated their beneficial impact on ectonucleotides activities, adenosine deaminase, and platelet aggregation in diabetic models.
Furthermore, research exploring the administration of grape seed extract (GSE), rich in procyanidins B1 and C1, during mesenchymal stem cell (MSC) transplantation in a streptozotocin-induced type I diabetes model revealed remarkable benefits. This combined GSE/MSC treatment significantly regulated glucose homeostasis and insulin secretion, alongside improvements in inflammatory markers and oxidative stress parameters.
Studies have also shown that quercetin, a component of grape pomace, effectively reduces blood glucose levels in intestinal cell models, corroborating the antidiabetic potential of the polyphenolic content in grape components.
Neuroprotective Properties
Oligomers of resveratrol, including (+)-vitisinol, (+)-ε-viniferin, (+)-ampelopsin A, (+)-vitisin A, and (-)-vitisin B, have demonstrated inhibitory effects on BACE-1 (beta-site APP-cleaving enzyme 1) in vitro. BACE-1 inhibition is an important target for the treatment of Alzheimer’s diseases as β-secretase in neurons is essential to produce beta-amyloid.
Studies with resveratrol have also shown positive results for the treatment of mice with Alzheimer’s related to age, disease, better cognition impairment, and increasing the lifespan of the animals.
Additionally, the administration of grape seed proanthocyanins (500 mg/kg) could improve abnormal peripheral nerve functions and impaired nervous tissues in the spinal cord of rats with type 2 diabetes mellitus.
Resveratrol has been found to promote neuroprotection by enhancing cellular antioxidant defenses and triggering neuroprotective pathways. This compound’s multifaceted action, observed in vitro in human cells and in vivo in rodents, offers protection against ischemic damage in the heart and brain, primarily due to its antioxidant, anti-inflammatory, and anti-apoptotic effects, along with other pathways.
Concluding Remarks
The potential health benefits of grapes and their derived compounds are undoubtedly promising. However, the existing limitations and clinical gaps, such as the need for comprehensive human-based clinical trials, investigations into bioavailability and metabolic pathways, and exploration of synergistic effects with conventional drugs, underscore the need for continued, rigorous research.
Addressing these clinical pitfalls will provide a more comprehensive understanding, paving the way for more definitive recommendations and applications in clinical settings. As research progresses, the focus should be on validating the efficacy of grape-derived bioactives in human health, determining optimal consumption guidelines, and uncovering the therapeutic potential of a broader range of grape varieties and their less-studied bioactives.
By embracing these future research directions, the potential of grapes in health maintenance and therapeutic interventions can be fully harnessed, bridging the gap from bench to bedside. For the latest updates on our winemaking journey and culinary delights, visit Wine Garden Inn.