BIOACTIVE COMPOUNDS EXTRACTION FROM BLACK TEA: COMPARISON OF CONVENTIONAL TECHNIQUES AND ADVANCED TECHNIQUES USING GREEN SOLVENTS

There are several methods for the extraction of phenolic compounds from natural products, ranging from classic to modern techniques. However, to achieve the selective extraction of specific compounds, it is necessary to resort to advanced techniques. The objective of this work was to evaluate the coupling two advanced techniques, pressurized liquid extraction (PLE) coupled to solid phase extraction (SPE), to compare it with conventional extraction techniques, as well as to evaluate the use of ethanol as a solvent in the process. The results obtained with the developed method were compared to those produced by ultrasound (37 and 80 kHz), stirring and Soxhlet (1 cycle and 5 cycles) extractions. The developed method produced one of the highest yields of gallic acid (1.45 ± 0.22 mg / g) but caffeine recovery (11.51 ± 0.58 mg / g) was lower than produced with ultrasound (37 kHz) (17.76 ± 0.97 mg / g), which was one of the most efficient techniques. PLE-SPE techniques yield the highest flavonoid extraction (7.95 ± 0.64 mg / g), even using ethanol as solvent. In this context, the advanced technique not only allowed high extraction yields with a lower volume of green solvent but also separated the compounds into different fractions (gallic acid: 60,88 ± 6,53 mg / L), caffeine (97,80 ± 3,97 mg / L) e flavonoids (201,40 ± 6,21 mg / L), being them: epicatechin, rutin, quercetin 3-O-galactoside, quercetin 3-O-glucoside, quercetin 3-O-galactosyl-rhamnosyl-glucoside, quercetin 3-(2G-p-coum-cis-3G)-2G-arabinosyl-3Rglucosylrutinoside, kaempferol 3-O-rutinoside, kaempferol 3-O-glucoside and theaflavin 3-gallate, providing significant advantages over the techniques and methods tested. These results indicate a potential for the advanced coupled PLE-SPE techniques and that ethanol can substitute methanol as an extraction solvent to exploit its benefits regarding cost, toxicity and sustainability.