## 2 Discussion
For example, anthocyanins can be chemically or enzymatically modified by acylation, glycosylation, and methylation [106,107] to produce more stable compounds. These compounds could be differentiated from the original by identifying, measuring, and quantifying through HPLC-TOF-MS, UV-vis, and HPLC. This is the case of the chemical synthesis of six novel pyranoanthocyanins that were obtained by our research group from anthocyanins delphinidin-3-O-sambubioside (D3S) and C3S, which were extracted and purified from the extracts of roselle calves (_Hibiscus sabdariffia_ L), which is widely used to prepare alcoholic and nonalcoholic refreshing beverages and infusions. These anthocyanins reacted with 4-vinylphenol, acetone, and butanone to synthesize novel pigments, purified and characterized by UV-vis and HPLC, and identified by MS [108]. The original anthocyanins D3S and C3G showed maximum absorptions at 526 and 518 nm, respectively. Nevertheless, the changes provoked by chemical modifications made to different spectra associated with the novel hydroxyphenyl-anthocyanins (\(\lambda_{\text{max}}\) 503 and 501 nm, respectively) and to the synthesized methyl-pyranoanthocyanins (\(\lambda_{\text{max}}\) 478 and 354, 475 and 340, 480 and 353, and 478 and 338 nm, respectively). The new pyranoanthocyanins have different spectroscopic properties compared with their original phenolics. Additionally, the search for more stable antioxidant compounds was conducted to the anthocyanin stabilization through the construction of physical barriers, such as the micro- or nanoencapsulation of the phenolic compounds. Through the construction of these polymeric or nanostructure matrices, anthocyanins can endure for long-time periods, and the evolution of their preservation can be followed by spectroscopic means. Furthermore, the specific properties of these antioxidant compounds can be followed during the shelf life of the vegetal, food product, or from the extracts obtained from that vegetal. An example of this is our previous work on the stabilization of blueberry extracts as an anthocyanin source. Blueberry is an important local product consumed as jams and beverages. Unfortunately, blueberry and its anthocyanins responsible for providing color are very unstable. Blueberry extracts were spray-dried using as an encapsulating agent mesquite gum affording a powder to stabilize the color. We proceeded to the powder evaluation in terms of color and anthocyanin content over time of storage. The evaluation consisted of the spectroscopic quantification of the total phenolic content, total anthocyanins, antioxidant capacity, and color [55]. Consequently, the polymeric wall usage was found to be effective in avoiding the losses of phenolics, anthocyanins, and color under different storage conditions (light and temperature). In terms of stability, our research group conducted another approach to look for the anthocyanin stabilization from coffee husks (_Coffea anabica_) by using ZnO nanoparticles. Herein, we were able to stabilize anthocyanins from the extracts obtained in this byproduct from the coffee industry. First, ZnO nanoparticles were successfully prepared following a previously described methodology [109] and used to stabilize the mentioned anthocyanins. Atomic absorption spectrometry was used to determine the mass of the anthocyanins coated by the ZnO nanoparticles by comparing the intensity of the signal obtained to a calibration curve previously prepared and convert the intensity into the zinc ion mass. The total mass of ZnO was stoichiometrically calculated and subtracted from the mass of the dried sample, obtaining the mass of the anthocyanins coating the nanoparticles (data unpublished). Another spectroscopic technique frequently employed is infrared spectroscopy. It is useful to follow the amount and stability of anthocyanins over time. In previous work, anthocyanins from _Hibiscus sabdariffa_ were used to dope titanium dioxide nanotubes and ensure more stability and capability for electrode regeneration.