Stability of Phenolic Compounds in Grape Stem Extracts

Area of Science:

• Agricultural Chemistry
• Food Chemistry
• Phytochemistry

Background:

• Grape stems are a valuable source of bioactive phenolic compounds, including stilbenes.
• These antioxidants possess health benefits but are susceptible to degradation during extract storage.
• Understanding the stability of these compounds is crucial for preserving their efficacy.

Purpose of the Study:

• To evaluate the stability of phenolic antioxidants in Mazuelo grape stem extracts.
• To determine the effects of storage temperature (25°C and 40°C) and light exposure (amber vs. transparent vials) on antioxidant degradation.
• To assess antioxidant stability over a 6-month storage period.

Main Methods:

• Mazuelo grape stem extracts were stored under controlled temperature and light conditions.
• Antioxidant concentrations, including gallic acid, quercetin derivatives, catechin, anthocyanins, resveratrol, and viniferin, were analyzed at 2, 4, and 6 months.
• High-performance liquid chromatography (HPLC) was likely employed for quantification.

Main Results:

• Gallic acid and quercetin derivatives remained stable throughout the storage.
• Catechin degraded completely within two months of storage.
• Anthocyanins were sensitive to temperature, with light exacerbating degradation at 40°C.
• Resveratrol and viniferin concentrations decreased over time, significantly affected by both temperature and light.

Conclusions:

• Storage conditions significantly influence the stability of key antioxidants in grape stem extracts.
• Catechin, anthocyanins, resveratrol, and viniferin are particularly vulnerable to degradation.
• Optimal storage conditions (e.g., lower temperature, protection from light) are necessary to preserve the antioxidant potential of grape stem extracts.