POLYPHENOLS PROFILE OF WILD THYME EXTRACTS OBTAINED BY CONVENTIONAL SOLID-LIQUID AND ULTRASOUND-ASSISTED EXTRACTION

Abstract

Thymus serpyllum extracts, potentially enriched with a wide spectrum of polyphenols, were subjected to LC-MS-MS analysis in order to determine their qualitative polyphenols profile. Analyses were conducted in the sample with the highest polyphenols yield and antioxidant activity obtained by conventional extraction using 60% of ethanol for 24 h at shaking speed of 150 rpm (Sample CE), sample obtained by ultrasound-assisted extraction at 65 °C for 55 min using 60% ethanol (Sample UAE-CP) and sample obtained at the temperature of 70.28 °C, extraction time of 70 min and using 45% ethanol as a solvent (Sample UAE-OPT). According to results of identification, the Sample UAE-CP contained the highest number of compounds, 31, a total of 30 different compounds were identified in the Sample CE and 27 compounds in the Sample UAE-OPT. Identified flavonoid subgroups were flavanones, flavan-3-ols, flavonols, flavones and isoflavones. Some of them were identified in aglycone form only. On the other side, flavanones were identified not only in aglycone form, but also in a form of their 7-O-glucoside, e.g. naringenin-7-O-glucoside. Finally, flavonols were identified in various forms, as compounds in aglycone form, then in form of their 3-O-glycosides with rutinose, glucose and galactose as the carbohydrate compounds, but in form of glucuronide and hexoside isomer as well. Identified phenolic acids were gallic, vanillic, ellagic, caffeic, 3-p-coumaroylquinic, 4-p-coumaroylquinic acid, coumaric acid hexoside isomer, p-coumaric, cis- and trans-coutaric acid. Taking into account the discrepancy in the polyphenols profiles of aforementioned extracts, it could be concluded that different extraction techniques under different extraction conditions or using different extraction solvent could be of a great importance for establishing the adequate polyphenols profile of T. serpyllum extracts.