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This study was undertaken to investigate the effects of hydrothermal treatments under mild acid and alkaline conditions on polyphenol release and recovery from wheat bran (WB). After an initial screening of various food-grade substances, strong evidence was raised regarding the potency of citric acid and sodium carbonate to provide WB extracts exceptionally enriched in polyphenols. Thus, these two catalysts were tested under various time and temperature combinations, and the processes were described by linear models based on severity factor. The most effective treatments were those performed with 10% of either citric acid or sodium carbonate, at a constant temperature of 90 °C for 24 h, providing yields in total polyphenols of 23.76 and 23.60 mg g−1 dry mass of ferulic acid equivalents, respectively. Liquid chromatography–mass spectrometry analyses revealed that, while the sodium carbonate treatment afforded extracts enriched in ferulic acid, treatments with citric acid gave extracts enriched in a ferulate pentose ester. The extracts produced from those treatments also exhibited diversified antioxidant characteristics, a fact ascribed to the different polyphenolic composition. To the best of the authors’ knowledge, this is the first report demonstrating the effective release of ferulic acid and a ferulate pentose ester from WB, using benign acid and alkali catalysts, such as citric acid and sodium carbonate.

Sambucus nigra flowers, known as elderberry flowers (EBF), are a plant tissue rich in polyphenolic phytochemicals with important bioactivities. However, there are few studies dealing with the production of polyphenol-containing EBF extracts. The objective of the investigation presented herein was the development of a high-performance green extraction methodology, to generate EBF extracts enriched in polyphenolic substances, using an efficient deep eutectic solvent, combined with ultrasonication pretreatment. The DES was composed of L-lactic acid (hydrogen bond donor—HBD) and glycine (hydrogen bond acceptor—HBA) and, after an initial screening to properly regulate HBD/HBA ratio, the extraction was optimized by deploying response surface methodology. Under the optimized conditions, which were DES/water (85% w/v), liquid-to-solid ratio 60 mL g−1, and stirring speed 200 rounds per minute, the extraction yield in total polyphenols amounted to 121.24 ± 8.77 mg gallic acid equivalents per g dry matter. The integration of ultrasonication prior to the batch stirred-tank extraction boosted polyphenol recovery of up to 174.73 ± 2.62 mg gallic acid equivalents per g dry matter. Liquid chromatography−mass spectrometry analysis showed that the richest EBF extract obtained was dominated by rutin, a di-p-coumaroylquic acid and chlorogenic acid.