Extraction of polyphenols from grape pomace using mixtures of non-ionic surfactants

Author: Jovan Baljak Scientific Coordinator: Mariola Herbet Institution: Department of Pharmacy, Faculty of Medicine, University of Novi Sad, Novi Sad, Republic of Serbia

INTRODUCTION: Grape pomace is a by-product accounting for 25% of grape mass used in the winemaking process and represents an economically viable source of polyphenols. The advantages of polyphenol extraction from pomace using surfactant solutions are solvent nontoxicity and process simplification.

AIM: Investigation of the influence of concentration and pH value of the solutions of non-ionic surfactants Brij® S20, poloxamer 407 and their mixtures on the efficiency of polyphenol extraction from pomace, based on the determination of total phenolic content and antioxidant capacity. Another aim was to determine the content of individual phenolics in extracts.

MATERIAL AND METHODS: Extraction of polyphenols from Cabernet Franc grape pomace was performed using solutions of non-ionic surfactants Brij® S20, poloxamer 407 and their mixtures (mass ratios: 9:1, 1:1, 1:9) in concentrations 3% and 5%, and pH values of 3,4 and 5. The total phenolic content in extracts was determined by the FolinCiocalteu method, antioxidant potential by the DPPH assay and the content of individual polyphenols by HPLC.

RESULTS: Optimal conditions for the polyphenol extraction from pomace by surfactant solutions were pH value 4 and mass concentration 3%. Extracts with the highest total phenol content (54.80 mg GAE/g grape pomace) and the highest antioxidant potential (IC50=1.80 µL/mL) were obtained using mixtures of Brij®S20 and poloxamer 407 (9:1 and 1:1), comparing to using solutions of non-ionic surfactants (34,82 mg GAE/g grape pomace and IC50=2.68 µL/mL). Mixtures of surfactants (9:1) show the greatest ability to solubilize water-insoluble polyphenol quercetin (2.38 mg/L), as well as watersoluble gallic acid (0.78mg/L), comparing to solutions of non-ionic surfactants (1.92 mg/L for quercetin and 0.67 mg/L for gallic acid).

CONCLUSION: Efficiency of the extraction depends on the extraction medium and factors such as concentration and pH value. Better extraction efficiency of surfactant mixtures is probably due to the synergistic effect in mixed micelles as a result of improved packaging of hydrophobic surfactant parts in the core of mixed micelles and increased micelles stability.

KEYWORDS: by-product; Brij® S20; poloxamer 470; solubilization

Questions & answers

Please, tell us a little bit more about yourself. My name is Jovan Baljak. I am a fourth-year Pharmacy student at the University of Novi Sad, Serbia, and I’m highly motivated to pursue a scientific research career in the fields of Pharmacy. I have worked as a student associate at Petnica Science Centre, Serbia. I have participated in implementation research projects for gifted high school students. I usually spend my leisure time travelling and discovering new cities. I also like cooking.

Tell us a bit more about your research and its significance. Last year I worked in the group of Prof. Jelena Helene Cvejić on obtaining polyphenolic compounds from grape pomace using nonionic surfactant extraction. The reason why we have chosen grape pomace is because grape pomace represents a by-product of the winemaking process and previous studies showed antioxidant and antiinflammatory effects of extract grape pomace. At greater concentrations of surfactants in the water solution micellar colloids begin to form in the bulk of the solution. Micelles have a role in development of pharmaceutical formulations as transport systems based on their potential to increase bioavailability of substances. The significance of our research is that we have found that extracts of grape pomace are showing some antioxidative potential and formulation extract and nonionic surfactant with the biggest amount of polyphenolic compounds, which are responsible for this effect. What was the biggest challenge while carrying out the research and how did you overcome that? The biggest challenge during the research was coordinating laboratory work with other student commitments, finals and the lack of laboratory equipment.

In your opinion, what is the benefit of joining ESSP and what advice do you have for students undertaking research in the future? In my view, the benefit of joining ESSP is a great opportunity to get experience for the future, make new contacts and present your research project. My advice for students is that everyone should work on at least one research project during study time because it develops your critical mindset.