Comparison of Conventional and Ultrasound-assisted Extraction Techniques on Mass Fraction of Phenolic Compounds from Sage (Salvia officinalis L.)

Sage (Salvia officinalis L.) is a popular herb which is native to the Mediterranean region and cultivated worldwide. Sage is an important source of antioxidants used as preservatives and has wider implications for the dietary intake of natural antioxidants.1,2 This antioxidant effect has been attributed to the main phenolic components, caffeic acid dimer – rosmarinic acid1 and flavonoids, being mostly present as flavones and their glycosides. Flavone glycosides are apparently common in sage, and most of them are flavones 7-glycosides represented by apigenin and luteolin 7-glucoside and their corresponding 3and 7-glucuronides.2 In the last few decades, research regarding the extraction of phenolic compounds found in plants have attracted special interest regarding their application in the food industry. Extraction is a very important step in the isolation, identification, and use of polyphenols.3 The conventional extraction methods, which have been employed for decades, require prolonged extraction times and relatively larger quantities of solvent.4,5 Therefore, various novel extraction techniques have been developed for the extraction of bioactive compounds from herbs, including ultrasound-assisted extraction,6–8 microwave-assisted extraction,9 supercritical fluid extraction.10 Ultrasound-assisted extraction is an upcoming extraction technique that can offer high reproducibility in shorter time, higher yields of bioactive compounds, simplified manipulation, decreased temperature during processing, reduced solvent consumption, and lower energy input.11–13 In our previous paper,5 the influence of solvent polarity and composition, time and temperature of conventional extraction on mass fraction of polyphenols from sage were researched. The mixtures of ethanol and water are possibly the most suitable solvents for the extraction of sage due to different polarities of the active constituents, and acceptability of this solvent system for human consumption.4,5 Albu et al.3 and Sališova et al.14 have investigated the difference in the application of conventional extraction and ultrasonic-assisted extraction on the concentration of biologically active compounds in sage. They concluded that the content of biologically active compounds is approximately 60 % higher under the influence of ultrasound. Rosmarinic acid is the more active of these antioxidants, but it is relatively easily degraded in solvent and the rate of degradation is solvent-dependant.6 The ultrasonic-assisted extraction has been widely used for obtaining polyphenols from plants using ethanol, mixture of ethanol/waComparison of Conventional and Ultrasound-assisted Extraction Techniques on Mass Fraction of Phenolic Compounds from Sage (Salvia officinalis L.)