Grapevine extract

While wine and grapes are the most known and valuable grapevine products, several waste products derive from this industry, such as must, grape water and leaves, the last being one of the most abundant waste products in the wine industry. This sub-product is considered a delicacy in many countries, including in the Mediterranean Basin. In fact, Mediterranean countries such as Turkey, Greece and Bulgaria cultivate specific grapevine cultivars especially for fresh and preserved leaf consumption.

The Mediterranean-type diet has been demonstrated to have numerous health benefits, namely on cardiometabolic diseases, diabetes and preventing certain types of cancer. Moreover, recently its impact in decreasing the risk of mental disorders, including depression, has also been highlighted. A wider inclusion of this disregarded by-product in the human diet or its use as a source of bioactive compounds is a good strategy, not only to introduce an added value to a waste product but also to come upon the European Union and United Nations’ demands towards more sustainable agricultural approaches and circular economy (Goals of the 2030 Agenda for Sustainable Development).

The increasing search for healthier diets as well as new products with health promoting characteristics, has drawn attention to grapevine leaves in the last few years. Grapevine leaves have already shown to be an excellent source of bioactive molecules, mainly phenolic compounds, and their antioxidant properties have been described to protect from and retard oxidative processes.

Leaves from Vitis vinifera L. represent the less studied and valorized wastes of grape crops and the winery industry. This study aims thus to perform for the first time a deepened assessment of the bioactive compounds in grapevine leaves. The detailed composition of main phytochemicals involved in the high antioxidant of grape leaves (2.20 g TE/100 g) was determined including:

• carotenoids (lutein, β-carotene)
• tocopherols (α and ɣ-tocopherol)
• polyphenols (phenolics acids, flavonoids)
• phytosterols (β-sitosterol)

In particular, high levels of lutein (0.3–1.0 g/kg) and α-tocopherol (0.2–1.2 g/kg) were observed. Moreover, the evolution of bioactive compounds during 7 harvesting times from July to October was also studied showing that the content of phytochemicals fluctuates according to the development stage of grape leaves. Phytosterols for example reached their highest levels in leaves in the later stage of maturation (T6 – T7) with values around 169 ± 40 mg/kg.

The studies have shown that grape leaves are the best source of resveratrol–they are up to one hundred times richer in resveratrol than the fruits. It is believed that plants produce resveratrol to help ward off fungus. The leaves are also rich source of quercitineas the whole plant.

References:

• Nzekoue FK, Nguefang MLK, Alessandroni L, et al: Grapevine leaves (Vitis vinifera): Chemical characterization of bioactive compounds and antioxidant activity during leave development. Food Bioscience; Vol.50, Part B, December 2022, 102120
• Fernandez F, Ramalhosa E, Pires P, et al.: Vitis vinifera leaves towards bioactivity; Industrial Crops and Products, 2013; Vol. 43, 434-440.
• Moldovan ML, Carpa R, Fizeşan L, et al.: Phytochemical Profile and Biological Activities of Tendrils and Leaves Extracts from a Variety of Vitis vinifera L. Antioxidants (Basel). 2020 May; 9(5): 373.
• Final European Union herbal monograph on Vitis vinifera L., folium - Revision 1; 2018,01, EMA, Committee on Herbal Medicinal Products (HMPC)

Resveratrol

Grape-Vine Leaf Extract (Vitis vinifera) is a rich source of numerous polyphenols from which resveratrol is the most important. Plants containing resveratrol have been used effectively in traditional medicine for over 2000 years. It can be found in some plants, fruits, and derivatives, such as red wine. Therefore, it can be administered by either consuming these natural products or intaking nutraceutical pills. Resveratrol exhibits a wide range of beneficial properties, and this may be due to its molecular structure, which endow resveratrol with the ability to bind to many biomolecules. Among these properties its activity as an anticancer agent, a platelet antiaggregation agent, and an antioxidant, as well as its antiaging, antifrailty, anti-inflammatory, antiallergenic, and so forth activities, is worth highlighting. These beneficial biological properties have been extensively studied in humans and animal models, both in vitro and in vivo. The issue of bioavailability of resveratrol is of paramount importance and is determined by its rapid elimination and the fact that its absorption is highly effective, but the first hepatic step leaves little free resveratrol. Clarifying aspects like stability and pharmacokinetics of resveratrol metabolites would be fundamental to understand and apply the therapeutic properties of resveratrol.

Resveratrol also has positive impact on the circulatory system (improves oxygenation of the body) and the immune system (improves immunity) and supports the detoxification of the body.

Quercetin

Quercetin is a plant pigment from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it. It has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.

Flavonoids, such as quercetin, are antioxidants. They scavenge particles in the body known as free radicals which damage cell membranes, tamper with DNA, and even cause cell death. Antioxidants can neutralize free radicals. They may reduce or even help prevent some of the damage free radicals cause. In test tubes, quercetin has strong antioxidant properties. But researchers are not sure whether taking quercetin (and many other antioxidants) has the same effects inside the body.

Hereinafter are listed some health conditions where quercetin consumption may have positive effect.

• Allergies, asthma, hay fever and hives
• Heart disease
• High cholesterol
• Hypertension
• Interstitial cystitis
• Prostatitis
• Rheumatoid arthritis (RA)
• Cancer
• Cataract
• AIDS
• Diabetes

In addition, quercetin has a protective effect on vitamins C and E, preventing the oxidation of ascorbate, through the possibility of chelation of copper ions and other transition metals. It strengthens blood vessels, thanks to which it supports the treatment of subcutaneous bleeding, hemorrhoids, varicose veins, as well as reduces blood clots, hence it also has anti-atherosclerotic properties.

Red Grape Leaf Extract (Red vine leaf extract = RVLE) brings relief to tired and swollen legs. It has a soothing, anti-swelling and relaxing effect. Red grape leaves contain active substances that have the ability to strengthen connective tissue. The red grape leaves contain ingredients that help to remove swelling of the feet and limbs and relieve pain, significantly supporting regenerative processes. The effect of red grape leaves has been confirmed in clinical trials. Preparations containing red grape leaf extract strengthen blood vessels and prevent them from breaking, improve circulation and effectively reduce leg pain caused by varicose veins.