Hazelnut kernel and byproducts: phytochemicals and biological activity
What it found
Hazelnut kernels and their processing byproducts contain phenolic compounds and other phytochemicals that show antioxidant, antiproliferative, and antimicrobial effects in lab tests.
Some of these effects were also seen in animals.
What they found
Animal and lab studies
Antioxidant activity in lab
Extracts from kernels and byproducts showed strong antioxidant activity in lab tests. Some isolated compounds, like giffonin D and H, reduced lipid peroxidation by more than 60% and 50% at 10 µM, more than the methanol extract or curcumin.
Antiproliferative effects in cells
In lab tests on human cancer cell lines, some hazelnut extracts and compounds reduced cell growth. For example, Oregon roasted hazelnut skin extract inhibited HT-29 colon cancer cell growth by 96% at 6 mg/mL after 4 days.
Antimicrobial effects in lab
Hazelnut extracts and compounds showed antimicrobial activity against certain bacteria and fungi in lab tests. Giffonin U and carpinontriol B at 40 µg/disk produced zones of inhibition comparable to tetracycline at 7 µg/disk against tested strains.
Prebiotic vs antimicrobial
Dietary fiber from hazelnut skins improved the growth of two Lactobacillus strains in lab fermentation, but free phenolic substances, especially proanthocyanidins, had a strain-specific antimicrobial effect against one strain.
Anticonvulsant in mice
In mice with pentylenetetrazole-induced seizures, an aqueous extract of hazelnut leaves increased the latency to first seizure, reduced lethality, and shortened convulsions, similar to sodium valproate.
Neuroprotection in rats
In ex vivo rat brain specimens, both Italian and Turkish hazelnut varieties increased norepinephrine levels and reduced dopamine levels after amyloid beta-peptide challenge.
Antiglycative effect in lab
An aqueous extract of Turkish hazelnut kernel showed more than 40% inhibition of advanced glycation end-product formation in a protein-glucose assay, but no inhibition in a protein-methylglyoxal assay.
Other findings
Phenolics most abundant
Phenolic compounds are the most abundant phytochemicals in hazelnut kernels and also in processing byproducts such as skins, shells, and leafy covers.
What the authors conclude
“contributing to highlight C. avellana as a source of bioactive phytochemicals with the potential to exert beneficial effects on human health.”
Also in their conclusions
- They conclude that C. avellana is a source of bioactive phytochemicals with the potential to exert beneficial effects on human health.
- They highlight that phenolics are the most abundant phytochemicals in kernels and byproducts.
- They note that analytical techniques for measuring these compounds have been reviewed.
How it was done
The authors wanted to update what is known about the chemistry and biological activity of specialized metabolites in hazelnut kernels and byproducts, and to review the analytical methods used to measure them.
They reviewed published studies on the chemistry, biological activity, and analysis of specialized metabolites in hazelnut kernels, skins, shells, leafy covers, leaves, and flowers.
What it can’t tell you
- Most of the biological effects were seen in lab tests or in animals, so they cannot show what happens in people.
- The review does not include human trials, so it cannot say whether eating hazelnuts causes any health effect in people.
- The amounts of compounds used in lab tests may not reflect the amounts absorbed from eating hazelnuts.
Who paid
- Conflicts
- The authors declare that they have no conflict of interest.
- Authors work at
- Università degli Studi di Salerno, Italy
The paper
- Title
- Plant Specialized Metabolites in Hazelnut (Corylus avellana) Kernel and Byproducts: An Update on Chemistry, Biological Activity, and Analytical Aspects
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Bottone A, Cerulli A, DʼUrso G, et al (2019). Plant Specialized Metabolites in Hazelnut (Corylus avellana) Kernel and Byproducts: An Update on Chemistry, Biological Activity, and Analytical Aspects. Planta medica. doi:10.1055/a-0947-5725Free full textPubMed 31250412DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error