Pressurized hot water extraction of phenolic compounds from leaves of Stevia rebaudiana: An UPLC‐ESI‐MSMS study

Abstract

AbstractBioactive polyphenolic compounds are present in Stevia rebaudiana leaves and pressurized hot water was applied for their extraction. The extraction was carried out at a constant pressure of 10.34 MPa and the effects of extraction parameters, temperature (100–160°C), time (5 and 10 min), and cycles (1–3) on the polyphenolic composition and content were determined [Correction added on 6 January 2020, after first online publication: the preceding sentence has been updated to reflect the correct temperature from “(10–160°C)” to “(100–160°C)”.]. A total of 33 polyphenolic compounds of four major categories namely phenolic acids, flavonols, flavones, and flavanols were determined in stevia extracts using UPLC‐ESI‐MS2, but the main polyphenolics were mono‐ and diacyl caffeoylquinic acids and quercetin glycosides. The observed pressurized hot water extraction parameters had a statistically significant effect on extraction yield of all analyzed stevia polyphenol subclasses. Cumulative effects of temperature and cycle number did not cause a significant difference in the extraction yield of flavan‐3‐ols. There was no difference in phenolic acids and flavonols with prolonged static extraction time at the highest temperature. Increasing the cycle number minimizes the effect of static time prolongation. The most suitable extraction conditions of stevia phenolic acids and flavanols were found to be at the 130°C and for flavonols and flavones at 160°C at the same extraction time of 10 min and 3 cycles.Practical ApplicationsThe major application of stevia extracts and stevioside is their use as a sweetener and dietary supplement. Apart from the sweet content, Stevia rebaudiana has numerous compounds with bioactive potential such as flavonoids and phenolic acids, sterols, triterpenoids, chlorophylls, alkaloids, lipids, essential oils, and trace elements. Past few years, stevia has attracted significant scientific interest as a natural antioxidant agent. Therefore, in this study, pressurized hot water extraction was optimized using water as generally recognized as safe solvent in order to establish an effective method for the production of stevia leaf extract rich in polyphenols. UPLC‐MS/MS analysis showed 33 different phenolic compounds belonging to the classes of phenolic acids, flavonols, flavones, and flavanols with mono‐ and diacyl caffeoylquinic acids and quercetin glycosides in the highest concentrations, indicating high potential of stevia leaves' extract for use in food and pharmaceutical industries.