Bergamot fiber shows promise in battling neurodegenerative disorders

By Dr. Chinta SidharthanJun 13 2023Reviewed by Benedette Cuffari, M.Sc.

In a recent study published in the journal Plants, researchers investigate the composition, antioxidant activity, flavonoid and polyphenol content, as well as other properties of bergamot fiber powder. The researchers also determined the effect of bergamot fiber on an in vitro neurotoxicity model induced by amyloid beta protein.

Study: Protective role of an extract waste product from Citrus bergamia in an in vitro model of neurodegeneration. Image Credit: THALERNGSAK MONGKOLSIN / Shutterstock.com

Background

Recent nutrition research promotes the consumption of vegetables and fruits as part of a balanced diet to reduce the risk of various chronic diseases. However, the large-scale consumption of vegetables and fruits in various forms results in the production of large quantities of waste products.

The estimated quantity of citrus waste products produced worldwide is close to 15 million tons annually. The bioactive content of these waste products necessitates an eco-friendly and responsible method of disposal, which subsequently increases disposal costs.

New regulations for food waste management have created the concept of byproducts, from which more bioactive compounds can be derived. Notably, citrus waste contains bioactive compounds with anti-inflammatory, anti-cancer, anti-infective, antioxidant, and neuroprotective activity, all of which have applications in treating hypertension, cancer, obesity, diabetes, and neurodegenerative disorders.

The citrus fruit Citrus bergamia or bergamot is grown in various regions throughout the world, including Italy, Antilles, Greece, and Canary Islands. It is used widely in the Mediterranean diet, as well as for cosmetics and perfumes. It is believed that the solid waste generated from the production of bergamot oil and juice contains numerous bioactive compounds that have therapeutic properties.

About the study

In the present study, researchers obtained bergamot oil, juice, and solid waste or “pastazzo” from bergamot harvested in February 2022 from the Bianco region of Italy. The solid waste was then ground, washed, and centrifuged to obtain a solid phase, which was then dried and powdered. A portion of this bergamot fiber powder was subjected to high-performance liquid chromatography (HPLC) to determine the bioactive content.

The oxygen radical absorbance capacity was measured to determine the antioxidant activity of the bergamot fiber powder. The Folin-Ciocalteu method was used to estimate the total phenolic content of bergamot fiber.

Additionally, the aluminum chloride-based colorimetric technique was utilized to determine the flavonoid content of the bergamot extract. The antioxidant activity of bergamot fiber was also measured using the 2,20-diphenyl-1 picrylhydrazyl (DPPH) assay.

To evaluate the neuroprotective properties of the bergamot fiber powder, the researchers acquired and cultured human neurons and oligodendrocytes. These cells were subsequently treated with bergamot fiber powder and amyloid beta protein. Colorimetric assays were used to evaluate the proliferation of the cells, whereas the Trypan blue exclusion assay was used to determine cytotoxicity.

The reactive oxygen species (ROS) content in treated cells was measured using 2',7'-dichlorodihydrofluorescein diacetate (H₂DCF-DA), where the cleaved H₂DCF binds to ROS and forms the fluorescent dichlorofluorescein (DCF). The concentration of proteins in the extract was also measured, while the annexin V staining method was used to assess the type of cell death. Additionally, immunoblot assays and immunofluorescence techniques with antibodies against the amyloid beta protein were used to identify specific proteins.

Study findings

The bergamot fiber powder contained flavonoids and polyphenols with antioxidant properties. In fact, the bergamot fiber protein exhibited neuroprotective effects against amyloid beta protein damage while also preserving cell viability and preventing ROS accumulation, caspase-3 expression and involvement, and apoptotic or necrotic death. Notably, the oligodendrocytes appeared to be more fragile and sensitive than the neurons.

The effects of increased concentrations of bergamot fiber powder were evaluated on neurons and oligodendrocytes. To this end, bergamot fiber fractions were not significantly toxic at the tested concentrations. Notably, even 10 µg/mL of bergamot fiber powder resulted in a significant decrease in cell mortality of amyloid beta-treated cells.

The chromatography techniques also revealed the presence of melitidine, brutieridine, neoeriocitrine, naringin, neohesperidine, and other polyphenols that have shown protective effects against Alzheimer’s disease-related neurodegenerative pathology.

Conclusions

To researchers of the current study examined the bioactive compounds and protein content of bergamot fiber powder and evaluated its antioxidant properties and concentration-dependent effect in an in vitro neurodegenerative model. The study findings indicate that bergamot fiber powder provided significant protection against amyloid beta protein-induced apoptosis in neurons and oligodendrocytes.

The antioxidant properties of bergamot fiber need to be further examined to determine its potential therapeutic applications against neurodegenerative conditions.