getpdf NLM PubMed Logo https://doi.org/10.17113/ftb.60.04.22.7443  

Increasing Antioxidant Activity in Food Waste Extracts by β-Glucosidase

Farahnaz Karami1,2orcid tiny, Mohammad Ghorbani1*orcid tiny, Alireza Sadeghi Mahoonak1orcid tiny, Alireza Pourhossein3orcid tiny, Ahmad Bagheri2orcid tiny and Reza Khodarahmi2,4*orcid tiny

1Department of Food Science and Technology, Gorgan University of Agricultural Sciences and Natural Resources, Basij street, 4918943464 Gorgan, Iran

2Medical Biology Research Center, Kermanshah University of Medical Sciences, Daneshgah street, 6714415185 Kermanshah, Iran

3Nano Drug Delivery Research Center, Health Technology Institue, Kermanshah University of Medical Sciences, Daneshgah street, 6714415153 Kermanshah, Iran

4Department of Pharmacognosy and Biotechnology, Faculty of Pharmacy, Kermanshah University of Medical Sciences, Daneshgah street, 6714415153 Kermanshah, Iran

Article history:

Received: 25 July 2021

Accepted: 2 June 2022

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Keywords:

antioxidant activity; β-glucosidase; oleuropein; quercetin; food waste

Summary:

Research backgroundFood by-products such as onion peels and olive leaves are rich in bioactive compounds applicable as natural and low-cost sources of antioxidants. Still, these compounds mainly exist in glycosylated form. Often, hydrolysis of glycoside compounds increases their antioxidant activity and health benefits. However, not many studies have been done concerning the β-glucosidase effect, specifically from Aspergillus niger, on glycosylated compounds within these by-products. Also, changes in the antioxidant activity of the mentioned by-products under the effect of β-glucosidase have not been reported yet. Therefore, this study considers the effect of A. niger β-glucosidase on glucoside compounds and the antioxidant activity of onion peel and olive leaf extracts.

Experimental approachThe antioxidant activity of the extracts was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Also, glucose, total phenolic and flavonoid contents were measured. Moreover, TLC and HPLC analyses were performed before and after the enzymatic hydrolysis.

Results and conclusionsThe obtained results showed an increase in the extract antioxidant activity after treatment. Also, β-glucosidase increased the glucose content of the extracts. The thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) results showed the β-glucosidase efficacy to hydrolyze quercetin glucosides in onion peel extract, and the quercetin concentration increased from (0.48±0.04) mg/mL in the untreated extract to (1.26±0.03) mg/mL in the treated extract (0.5 % m/V) after 3 h of enzymatic hydrolysis at 45 °C. Also, the content of quercetin-3-O-glucoside increased considerably from (1.8±0.1) to (54±9) μg/mL following the enzyme treatment. Moreover, oleuropein in olive leaf extract (1 % m/V) was hydrolyzed completely from (0.382±0.016) to 0 mg/mL by β-glucosidase for 24 h at 50 °C. 

Novelty and scientific contributionThis study showed that A. niger β-glucosidase, as a stable enzyme, hydrolyzed quercetin and oleuropein glycosides in onion peel and olive leaf extracts. Thus, A. niger β-glucosidase is a good candidate for processing the food waste and extracting valuable bioactive compounds. Also, the treated extracts with higher antioxidant and biological activity, and without bitter taste can be applicable as potent, natural and cost-effective antioxidants in the food industry.

*Corresponding authors: +989112754553
  moghorbani@yahoo.com
  +989122388184
  rkhodarahmi@mbrc.ac.ir

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