Developing and optimizing methods for grape seed polyphenol extraction
Lahiru RANEPURA HEWAGE
Date of Award
Master of Medical and Health Science by Research
School of Medical and Health Sciences
Ralph N. Martins
W.M.A.D. Binosha Fernando
Abuelgassim Omer Abuelgassim
Dietary polyphenols have been positively correlated to the reduced risk of several chronic diseases, including Alzheimer' disease (AD). Grape (Vitis vinifera) seed contains 5-8 % polyphenols and annually, 2.5 million tonnes of grape seed is generated in the juice and wine industry. Grape seed extract (GSE) and its compounds gallic acid (GA), resveratrol (RSV) and epigallocatechin gallate (EGCG) have been shown to attenuate AD aetiological features including oxidative stress, protein aggregation, and mitochondrial dysfunction in cell and animal models. The main objectives of this work were to optimize the methods for grape seed polyphenol extraction and assess their antioxidant properties. Polyphenols from grape seeds were extracted using ethanol, methanol, and acetone as solvents. Total phenolic content (TPC), and total flavonoid content (TFC) of GSEs were determined by Folin-Ciocalteu’s and AlCl3 colorimetric methods. Free radical scavenging activities were measured using standard antioxidant assays (DPPH and ABTS) and levels of GA, EGCG, and RSV were determined by high performance liquid chromatography (HPLC). Findings from this study showed the highest TFC levels in acetone extraction that was consistent with previous studies. Ethanol showed improved extraction of phenolic compounds compared to acetone and better than methanol in overall polyphenol extraction.
Ethanol extracted GSEs exhibited high free radical scavenging capacity measured using ABTS and DPPH demonstrating its potent antioxidant activity. Ethanol extracted GSEs displayed the highest ABTS scavenging ability as compared to acetone and methanol extractions. Ethanol extracted GSEs showed high free polyphenols content but low level of bound polyphenols. The TFC, TPC and radical scavenging properties of the free polyphenol fraction was significantly higher than those of the bound polyphenol fraction from GSE. Thus, potential therapeutic effects of GSE may be attributed to the free polyphenol fraction. GA and EGCG were detected in both unbound and bound phenolic extracts. However, RSV was only detected in bound polyphenol extract. Overall, the findings presented here have unravelled new insights into the polyphenol content of GSEs, solubility, efficiency of different extraction conditions and more importantly generated new knowledge that will be critical for developing industrial processes for developing GSE as a commercial food product for alleviating AD.
Access to this thesis is embargoed until 31st March 2024
Ranepura Hewage, L. P. (2023). Developing and optimizing methods for grape seed polyphenol extraction. https://ro.ecu.edu.au/theses/2645