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Phenolic Acids in Jerusalem Artichoke (Helianthus tuberosus L.): Plant Organ Dependent Antioxidant Activity and Optimized Extraction from Leaves

Department of Biotechnology, Inland Norway University of Applied Sciences (INN), Campus Hamar, Holsetgata 31, 2318 Hamar, Norway
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Molecules 2019, 24(18), 3296; https://doi.org/10.3390/molecules24183296
Received: 14 August 2019 / Revised: 6 September 2019 / Accepted: 8 September 2019 / Published: 10 September 2019
Phenolic acids including chlorogenic acids are major polyphenolic compounds found in Jerusalem artichoke (Helianthus tuberosus L.). The plant itself is an emerging biorefinery crop due to the inulin-rich tubers, a bioethanol feedstock, but the aerial parts represent a rich source of bioactive compounds. We have determined the level of major phenolic acids in extracts of four plant organs: tuber, leaf, flower, and stem. Employing three heating conditions (20 °C, 60 °C, and microwaving), corrected total phenolic content (TPC) was highest in the leaves (4.5–5.7 mg gallic acid equivalents g−1 dry substance), followed by flower (2.1–2.9), tuber (0.9–1.4), and lowest in stem extracts (0.1–0.2). A previously overlooked interference of the Folin–Ciocalteu assay, namely a signal contribution from ascorbic acid, caused overestimation of TPC in various organs ranging from 65% to 94%. Radical scavenging activity of extracts correlated significantly with TPC, both on corrected (R2 = 0.841) and uncorrected (R2 = 0.884) values. Out of the identified phenolic acids determined by quantitative HPLC-UV analysis, chlorogenic and dicaffeoylquinic acids accounted for 72–82% of corrected TPC in leaf and tuber extracts. Optimization of leaf extraction was tested in a 23-factorial Central Composite Face (CCF) design. Temperature was the most important model term, and a solvent strength of less than 50% ethanol promoted the highest TPC yields. Further developments in extraction processing of crop residues may open avenues for improving the utilization of Jerusalem artichoke in valuable products. View Full-Text
Keywords: Jerusalem artichoke; chlorogenic acid; total phenolic content; ascorbic acid; antioxidant activity; yield Jerusalem artichoke; chlorogenic acid; total phenolic content; ascorbic acid; antioxidant activity; yield
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Showkat, M.M.; Falck-Ytter, A.B.; Strætkvern, K.O. Phenolic Acids in Jerusalem Artichoke (Helianthus tuberosus L.): Plant Organ Dependent Antioxidant Activity and Optimized Extraction from Leaves. Molecules 2019, 24, 3296.

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