Comparison of green technologies for valorizing sugar beet (Beta vulgaris L.) leaves

This study is focused on valorizing sugar beet (Beta vulgaris L.) leaves, a prominent by-product wasted during the process of sugar beet. For doing so, Ultrasound-Assisted Extraction (UAE), Pressurized Liquid Extraction (PLE), and Maceration Extraction (ME) methods were compared by evaluating the extraction yield, Total Phenolic Compounds (TPC), Total Flavonoid Content (TFC), individual phenolic profile, and antioxidant activity (i.e., DPPH, FRAP, and ABTS). EtOH 70% was employed as the extracting solvent. The TPC for UAE and PLE methods was 4.90±0.083 and 6.46±0.33 mg GAE.mL-1, respectively, differing significantly (P<0.05) from each other. Moreover, the extract obtained by the PLE method had the highest TFC (1.45±0.06 mg QE.mL-1). The antioxidant activity of PLE extract was higher than other samples, differing significantly (P<0.05) in FRAP and ABTS methods. Benzoic acid was present only in the PLE extract, while PLE and ME recovered the highest quantity of syringic acid (0.35±0.00 mg.mL-1) and pyrogallol (74.80±0.01 mg.mL-1), respectively. However, the extraction yield obtained by the UAE method (19.58±0.33%) was significantly higher than the other methods. Therefore, despite the higher TPC and antioxidant activity achieved by the PLE method, it was proved that UAE yields higher polyphenolic compounds with a lower quantity of beet leaves.