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Article

Optimization of Ultrasound-Assisted Extraction of Phloretin and Other Phenolic Compounds from Apple Tree Leaves (Malus domestica Borkh.) and Comparison of Different Cultivars from Estonia

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ERA Chair for Food (By-) Products Valorisation Technologies VALORTECH, Estonian University of Life Sciences, Kreutzwaldi 56/5, 51006 Tartu, Estonia
2
Polli Horticultural Research Centre, Estonian University of Life Sciences, Uus 2, 69108 Polli, Estonia
*
Authors to whom correspondence should be addressed.
Academic Editor: Soraya Rodríguez Rojo
Antioxidants 2021, 10(2), 189; https://doi.org/10.3390/antiox10020189
Received: 6 January 2021 / Revised: 22 January 2021 / Accepted: 25 January 2021 / Published: 28 January 2021
Polyphenolic compounds, plant secondary metabolites essential for plant survival, are known for their high antioxidant and anti-inflammatory activity. In addition, several polyphenols, such as phloretin, also have potential antiviral effects, making these compounds potential ingredients of biofunctional foods. A promising source for the extraction of phloretin is a by-product of apple production—apple tree leaves. Focusing on green technologies, the first aim of the present study was to optimize the direct ultrasound-assisted extraction conditions to gain the maximum yield of phloretin from air-dried apple leaves. For the optimization of process parameters, we applied the response surface method with Box–Behnken design. The optimal extraction conditions were extraction time 14.4 min, sonication amplitude 10% and 10 g of sample per 100 mL solvent (70% ethanol, w/w). Using these conditions, we assessed the content of individual and total polyphenolic compounds along with antioxidant activity in the leaves of different autumn and winter apple cultivars grown in Estonia. The analyses were carried out with chromatographic (HPLC-DAD-MS/MS) and spectrophotometric methods. The phloretin concentration ranged from 292 to 726 µg/g and antioxidant activity from 6.06 to 11.42 mg GA eq./g, these being the highest in the local winter cultivars ‘Paide taliõun’ and ‘Tellissaare’, respectively. View Full-Text
Keywords: Malus domestica; leaves; agri-food waste valorisation; polyphenols; phloretin; antioxidant activity; ultrasound-assisted extraction; optimization Malus domestica; leaves; agri-food waste valorisation; polyphenols; phloretin; antioxidant activity; ultrasound-assisted extraction; optimization
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MDPI and ACS Style

Ben-Othman, S.; Kaldmäe, H.; Rätsep, R.; Bleive, U.; Aluvee, A.; Rinken, T. Optimization of Ultrasound-Assisted Extraction of Phloretin and Other Phenolic Compounds from Apple Tree Leaves (Malus domestica Borkh.) and Comparison of Different Cultivars from Estonia. Antioxidants 2021, 10, 189. https://doi.org/10.3390/antiox10020189

AMA Style

Ben-Othman S, Kaldmäe H, Rätsep R, Bleive U, Aluvee A, Rinken T. Optimization of Ultrasound-Assisted Extraction of Phloretin and Other Phenolic Compounds from Apple Tree Leaves (Malus domestica Borkh.) and Comparison of Different Cultivars from Estonia. Antioxidants. 2021; 10(2):189. https://doi.org/10.3390/antiox10020189

Chicago/Turabian Style

Ben-Othman, Sana, Hedi Kaldmäe, Reelika Rätsep, Uko Bleive, Alar Aluvee, and Toonika Rinken. 2021. "Optimization of Ultrasound-Assisted Extraction of Phloretin and Other Phenolic Compounds from Apple Tree Leaves (Malus domestica Borkh.) and Comparison of Different Cultivars from Estonia" Antioxidants 10, no. 2: 189. https://doi.org/10.3390/antiox10020189

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