Antioxidative polyphenols from walnuts (Juglans regia L.)

Area of Science:

• Phytochemistry
• Natural Products Chemistry
• Biochemistry

Background:

• Walnuts (Juglans regia L.) are a source of diverse bioactive compounds.
• Hydrolyzable tannins and polyphenols are known for their potential health benefits.
• Understanding the specific compounds and their activities is crucial for potential applications.

Purpose of the Study:

• To isolate and characterize novel hydrolyzable tannins from walnut seeds.
• To evaluate the antioxidant and radical scavenging activities of isolated compounds.
• To identify potential therapeutic agents from natural sources.

Main Methods:

• Extraction of walnut seeds using n-BuOH.
• Isolation of compounds using chromatographic techniques.
• Structure elucidation using spectral (NMR, MS) and chemical evidence.
• Assay of superoxide dismutase (SOD)-like activity.
• Measurement of radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals.

Main Results:

• Three new hydrolyzable tannins, glansrins A-C, were isolated and characterized as ellagitannins.
• Adenosine, adenine, and 13 known tannins were also identified.
• The 14 isolated walnut polyphenols demonstrated significant SOD-like activity (EC50: 21.4–190 μM).
• These compounds exhibited potent DPPH radical scavenging effects (EC50: 0.34–4.72 μM).

Conclusions:

• Walnut seeds are a rich source of ellagitannins with potent antioxidant properties.
• Glansrins A-C represent novel compounds with significant SOD-like and DPPH radical scavenging activities.
• These findings highlight the potential of walnut-derived polyphenols as natural antioxidants.