**4. Phenolic compounds in maize by grain color**

The content and type of phenolic compounds in the maize grain will vary depending on the color of the grain, the genetic origin, and the extraction method used. In the latter factor is determining if technologies such as ultrasound and microwave to favor extraction are used, in addition to the type of solvent used to extract them. **Table 2** contains information regard‐ ing the amount of free or bound soluble and insoluble phenolics found in maize grain. The data show very large differences in the reported values by different authors for the same maize grain color. This is undoubtedly due to the genetic variability of the biological material itself. Furthermore, in some works as that of Montilla et al. [29], the extraction of the insoluble phenolic was performed sequentially with three different hydrolysis methods and finally the phenolic compounds recovered from each were added. This method differs from what has been done, for example, by López‐Martínez et al. [30], who performed alkaline hydrolysis and recovered the phenolics by liquid‐liquid extraction with ethyl acetate, which is the most common method applied. Under this method, the authors reported very different values in four samples of purple grain of different genetic background.
