Effects of Temperature and Time on Polyphenolic Content and Antioxidant Activity in the Pressurized Hot Water Extraction of Deodorized Thyme (Thymus vulgaris)
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Date
2012
Journal Title
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Volume Title
Publisher
AMER CHEMICAL SOC
Abstract
The effects of temperature (50-200 degrees C) and contact time (5-30 min) on the pressurized hot water extraction of deodorized thyme were explored for antioxidant activity, polyphenol profiles, and total antioxidants. Six not previously reported polyphenolic compounds were identified in thyme. An inverse correlation was found between the antioxidant activity and total antioxidants with the amount and diversity of polyphenols. The highest total extract yield and antioxidant activity were obtained at 200 degrees C, although maximum polyphenol extraction yields of hydroxycinnamic acids, flavones, flavonols/flavanones, and total polyphenols were detected at 100 degrees C and 5 min. Higher temperatures and longer exposure times reduced extract polyphenol diversity. Dihydroxyphenyllactic acid was the only phenolic compound for which extraction yield increased with temperature, probably as a product of the thermal degradation of rosmarinic acid. Consequently, for extracting phenolics from thyme, 100 degrees C and 5 min would be appropriate operating conditions, whereas antioxidant active nonphenolic compounds were favored at higher temperatures and exposure times.
Description
Keywords
pressurized hot water, thermal degradation, rosmarinic acid, Thymus vulgaris, LC-MS, TANDEM MASS-SPECTROMETRY, SUBCRITICAL WATER, PHENOLIC-COMPOUNDS, FUNCTIONAL-CHARACTERIZATION, CHROMATOGRAPHIC TECHNIQUES, DIETARY POLYPHENOLS, OFFICINALIS L., CAFFEIC ACID, HERBAL DRUGS, WILD THYME