Botanical Extraction

Grapevine Pruning Waste as an Innovative Source of Phenolic Compounds

Written by Sabina Pulone

Plants are an inexhaustible source of molecules beneficial for human health. There’s always interest in botanical food supplements and herbal preparations, however, there is still a lack of a deep understanding of the qualitative and quantitative composition of many plants and the best techniques to isolate phytochemicals therein. This dearth exists even though many plant-derived products are commercially available and have been used since antiquity.

The application of environmentally safe and innovative extraction methods, in combination with traditional ones, can lead to a maximization of natural, biologically active molecules in the final product. Dietary polyphenols, such as phenolic acids and flavonoids, are a primary source of antioxidants and anti-inflammatory agents for humans and are derived from plants including fruits, vegetables, spices, and herbs. [1] Current literature suggests that the long-term consumption of diets rich in polyphenols protects against cardiovascular diseases, oxidative stress, certain types of cancers, type 2 diabetes, osteoporosis, pancreatitis, gastrointestinal problems, lung damage, and neurodegenerative issues as well as other diseases. [2]

Vitis vinifera (common grapevine) is one of the most used herbal materials to extract polyphenolic compounds. The traditional extraction method involves the cold maceration of fresh plant material in a mixed solvent solution including ethanol, water and glycerine for 21 days. Grapevine young sprouts and buds are more concentrated in bioactive substances, but there is a limited availability of them due to the collecting time during the cold season. For this reason, the production of polyphenolic food supplements from grapevines is more expensive than other plants and sources other than young buds have been investigated as alternatives.

In this context, a recent scientific study reported the use of V. vinifera by-products as alternative feedstocks for the production of phenolics-rich supplements using new faster and greener extraction technologies. [3] Grapevine pruning wood extracts have been obtained using ultrasonic-assisted techniques and then analysed through spectroscopic (fluorescence and ultraviolet/visible) and chromatographic methods (high performance liquid chromatography) to assess the quality and composition of these products compared to traditional bud-macerate extracts and commercially available bud preparations.

The ultrasonic-assisted extraction (UAE) was used in pulse mode (PUAE) instead of continuous mode to avoid excessive heat production and the possible thermal degradation of bioactive molecules in the final extract. Various phenolic compounds including flavonols, benzoic acids, catechins, and cinnamic acids have been used as markers for the potential health promoting activity and the antioxidant capacity of the extracts. Flavonols were the most abundant phenolic compounds in ultrasound extracts (45%), while phenolic acids were found to be the major substances in bud-macerated and commercially analyzed bud-extracts (49% and 50%, respectively).

Nevertheless, the ultrasound-assisted extracts provided higher absorbances in the ultraviolet/visible spectral region compared to traditionally made extracts, meaning that, at the same dilution, there is a higher concentration of extracted polyphenolic compounds. The use of different extraction techniques such as PUAE on the same plant material can offer alternative methods to produce new herbal preparations in faster and more effective ways with similar phytochemical composition to traditional preparations. More studies should be done with similar approach on other plant species to improve the total production system and maximize extraction efficiencies.

References:

[1] Martin K, Appel CL. Polyphenols as dietary supplements: A double-edged sword. Nutrition and Dietary Supplements. 2010;2:1-12. [journal impact factor = 0.146; times cited = 301]

 

[2] Cory H, Passarelli S, Szeto J, Tamez M, Mattei J. The role of polyphenols in human health and food systems: A mini-review. Front Nutr. 2018;5:87. [journal impact factor = 6.576; times cited = 454]

 

[3] Donno D, Turrini F, Boggia R, et al. Vitis vinifera L. pruning waste for bud-preparations as source of phenolic compounds-Traditional and innovative extraction techniques to produce new natural products. Plants (Basel). 2021;10(11):2233. [journal impact factor= 3.899; times cited = 0]

 

Image: https://www.pexels.com/photo/several-bunch-of-grapes-760281/

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Sabina Pulone

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