Design and optimization of “greener” and sustainable ultrasound-assisted extraction of valuable bioactive compounds from common centaury (Centaurium erythraea Rafn) aerial parts: A comparative study using aqueous propylene glycol and ethanol

Abstract

The design of two environmentally friendly protocols regarding ultrasound-assisted extraction (UAE) of valuable bioactive compounds from common centaury (Centaurium erythraea Rafn, Gentianaceae) aerial parts with aqueous mixtures of „green“ organic solvents (ethanol and propylene glycol) was conducted. In order to ensure the maximum total polyphenolic content (TPC), Box-Behnken experimental design (BBD) was used for both UAE/aqueous ethanol (UAE/aEtOH) and UAE/aqueous propylene glycol (UAE/aPPG) systems to optimize time, solvent concentration, liquid-to-solid ratio and temperature. The liquid-to-solid ratio had the highest effect on the TPC for tested extraction systems. For UAE/aEtOH system under the optimal conditions the predicted and experimentally obtained TPC were close (4.11 and 4.13 ± 0.04 g GAE/100 g d.w., respectively). The predicted and experimentally obtained TPC for UAE/aPPG system under the optimum conditions were 4.12 and 4.16 ± 0.04 g GAE/100 g d.w., respectively. According to UHPLC-DAD-MS/MS analysis, key bioactive components in both extracts were organic acids and derivates, flavanols, xanthones and secoiridoid glycosides. UAE/aPPG and UAE/aEtOH extracts contained 45 and 42 compounds, respectively. Since these extracts can be incorporated into different products as natural active ingredients, the extraction protocols are likely to ensure easy transfer to a large-scale production and further utilization in different industries, specifically ensuring cleaner production with reduced impact on the environment. Moreover, the usage of ethanol and its presence in the final industrial products has downsides: evaporation, flammability, irritation of different organs, discouraged use for some consumers due to preexisting medical conditions, interactions with various prescribed medicines, ethical reasons, etc. Thus, a much safer UAE/aPPG system, providing extract with more biologically functional phytochemicals and higher TPC at a lower temperature, is more recommended for eco-friendly future industrial use.