5-Hydroxymethyl-2-furfural and Derivatives Formed during Acid Hydrolysis of Conjugated and Bound Phenolics in Plant Foods and the Effects on Phenolic Content and Antioxidant Capacity

• Published in: Journal of agricultural and food chemistry Vol. 62; no. 20; pp. 4754 - 4761
• Main Authors: Chen, Peter X, Tang, Yao, Zhang, Bing, Liu, Ronghua, Marcone, Massimo F, Li, Xihong, Tsao, Rong
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 21.05.2014; American Chemical Society, Books and Journals Division
• Subjects: absorption; acid hydrolysis; Acids - chemistry; antioxidant activity; Antioxidants - chemistry; Chromatography, High Pressure Liquid; ethanol; foods; free radical scavengers; Fruit - chemistry; fruits; Furaldehyde - analogs & derivatives; Furaldehyde - chemistry; grains; hydrochloric acid; Hydrolysis; hydroxymethylfurfural; methanol; nuclear magnetic resonance spectroscopy; phenolic compounds; Phenols - chemistry; Plant Extracts - chemistry; reactive oxygen species; solvents; Tandem Mass Spectrometry; temperature; vegetables; Vegetables - chemistry; NMR; HPLC-DAD; hydroxymethylfurfural; plant extraction; methoxymethylfurfural; furans; ethoxymethylfurfural; fructose; dehydration; LC−MS
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf500518r

A common protocol for the extraction of phenolic aglycons or bound phenolics in plants generally involves hydrothermal hydrolysis in an aqueous methanol or ethanol solution containing 2–4 N HCl. However, as shown in the present study, this process also forms 5-(hydroxymethyl)furan-2-carbaldehyde (HMF) and its derivative products 5-(methoxymethyl)furan-2-carbaldehyde (MMF) and 5-(ethoxymethyl)furan-2-carbaldehyde (EMF), as identified by HPLC-DAD–ESI-MS/MS and NMR. These compounds are commonly misidentified as phenolics due to similar UV absorption at 280 nm. In this study, production of HMF, MMF, and EMF was shown to be dependent on the solvent condition and duration and temperature of hydrolysis. Fruits and vegetables produced HMF more readily than grains. HMF and its derivatives were subjected to various spectrophotometric antioxidant assays [2-diphenyl-1-picryhydrazyl radical scavenging activity (DPPH), ferric-reducing antioxidant power (FRAP), and oxygen radical absorbing capacity (ORAC)] and displayed antioxidant activity mainly in the ORAC assay. Results of this study help avoid overestimation of phenolic content and antioxidant activities of plant foods.