## 2 Discussion
Meanwhile, the ABTS test uses the green-colored radical ABTS** by ABTS oxidation with potassium persulfate. Similar to that observed for DPPH, ABTS** stabilizes through the reduction provoked by the antioxidant compound. The result is a colorless solution that can be spectrophotometrically followed at 415 nm [69]. This methodology allows the evaluation of both hydrophilic and lipophilic substances. The results are expressed referring in comparison to the standard scavenger Trolox, a vitamin E analog that serves to construct a calibration curve. Trolox equivalents (TEs) indicate the antioxidant present for both assays [77]. Previous works have dealt with the evaluation of the antioxidant activity of several vegetal products and extracts obtained from them, which is the case of diverse berries [78], grapes [79], wines [80], kiwi [81], tea [82], ginger [83], carrot [84], quinoa [85], maize [86; 87], ginkgo [88], and so on. In our laboratory, we have been working on several vegetables to evaluate their antioxidant properties for diverse purposes. This is the case of the evaluation of the antioxidant activity retention of spray-dried blueberry extracts [55]. In this work, we report the high antioxidant activity of blueberry extracts (116.2 TE/g soluble solid of the blueberry extract) following the abovementioned spectrophotometric ABTS assay [89]. The time evolution of the spray-dried extracts from the blueberry is also spectrophotometrically followed. These extracts reach values as high as 101.89-102.22 TE/g ss berry extracts, corresponding to antioxidant activity retentions of more than 87% in some of the prepared capsules. In addition, we reported on the evaluation of phenolic compounds to measure the antioxidant activity of the extracts from pigmented maize (_Zea mays_), roselle calyxes (_Hibiscus sabkariffsa_), mamey (_Pouteria sapota_), coffee fruit (_Coffea arabica_), carrot (_Daucus carota_), and passion fruit (_Passiflora edulis_). A study focused on the antioxidant activity of anthocyanins from _Hibiscus sabkariffsa_ L. [90] deals with the measuring of roselle petals' extracts cultivated in Taiwan. In this work, the antioxidant activity was measured through FRAP, ORAC, and total antioxidant status (TAS) assays. It is noteworthy that the extraction time was positively correlated with the antioxidant activity of the extracts. In this regard, the longer was the extraction the most antioxidant activity of the extracts was detected, no matter the methodology employed. Additionally, there was a linear relationship between all the assays probed in this work. As well, other authors have made evident the reducing capacity of the extracts of roselle attributed to the presence of anthocyanins, either using the ABTS, DPPH, or ORAC methodologies [91; 92]. Related to the extraction of anthocyanins from roselle, [PERSON] et al. [93] established a mathematical model to predict the thermo-degradation kinetics of water-extracted anthocyanins. For this purpose, total monomeric anthocyanins were spectrophotometrically measured using the pH differential method (510 nm). In this way, it was possible to spectrophotometrically follow the degradation of anthocyanins to construct a mass transfer model. For the pigmented maize, some studies have enabled the identification of anthocyanins present in this product. [PERSON] and [PERSON] [94] obtained the HPLC profiles of the anthocyanins present in powders from purple maize cobs using a diode array detector (DAD). The results showed the presence of C3G as the major anthocyanin present in this pigmented grain, followed by cyanidin-3-malonylglucoside (C3 MG), peonidin-3-O-glucoside (P3G), pelargonidin-3-(6\"-malonyl-glucoside) (PG3(6 MG)), pelargonidin-3-O-glucoside (PG3G), and peonidin 3-(6\"-malonyl-glucoside) (P3(6 MG)). In this sense, we have been working on the extraction, quantification, and identification of anthocyanins from blue maize from central Mexico (unpublished data).