## 1 Introduction
Currently, the green chemistry-based extraction methods could be a better option against the conventional extraction methods (CE) to meet the circular economy goals, avoiding the negative environmental impact of these methods related to high time and energy consumption, and toxic solvents usage [14]. The extraction is an essential step in the production of antioxidant extracts for food ingredients formulation since it is imperative to obtain higher concentration of target compounds while minimizing the concentration of the other compounds that could interfere with the extract quality and stability, which make them undesired in this extract, despite their nutritional value. Moreover, the extraction should be easy, low-cost, harmless, reproducible and suitable for industrial scale-up [15]. Green chemistry-based extraction methods such as microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE), has been widely explored for the recovery of polyphenols from different by-products once these methodologies demonstrate higher yield in less time while reducing solvent and energy consumption [16]. UAE requires less extraction time than CE because the contact surface between the solid and liquid phases, increases by partial destruction due to the cavitation process [17]. On the other hand, MAE enables that extraction to be heated by the interaction with the free molecules present, which leads to the destruction of fruit tissue and the release of the BCs into the solvent by the combination of high temperature and pressure. Furthermore, in both methods, the extraction time is shortened to only a few minutes in relation to 1-20 h with conventional extractions [17]. Until now, to the best of our knowledge, there are no studies applying MAE and UAE to non-compliant BE apples in order to develop natural antioxidant extracts. Notwithstanding, our research group already carried out similar works with non-compliant cherry to produce antioxidant extracts [15]. The main purpose of this research work was comparedtwo green extraction techniques (MAE and UAE) with CE (with low and high temperatures) to observe the best technique to produce a natural antioxidant extract rich in polyphenols from non-compliant BE apple for further food applications. Thereupon, other variables such as type of solvent, solvent/mass ratio, time and temperature were not considered for the study since studies of optimization of these parameters for several matrices, including apple pomace and apple peels, were already reported in the literature [18; 19; 20]. The solvent used, a mixture of ethanol and water (50:50, _v:v_), was selected based on results obtained in previous studies with different mixture percentage of ethanol in the mixture. The solvent ethanol and water (50:50, _v:v_) is considered (i) food grade, (ii) environmentally friendly, (iii) could be reused in the process, and finally (iv) this mixture is one of the most common mixtures of solvents used to produce extracts rich in phenolic compounds [15]. The four different antioxidant extracts developed were evaluated regarding their phenolic compounds composition and antioxidant capacity using chemical in vitro assays.