Phenolic compounds are plant second

Phenolic compounds are plant secondary metabolites including a variety of compounds such as phenolic acids, flavonoids, stilbenes, coumarins and tannins. Avocado is not valued as good a source of phenolics as some other fruit (e.g. soft fruit), probably explaining why investigation into the polyphenolic profile of avocado has remained scarce. Most information on phenolic content has been carried out principally to understand better the economic significance and mechanism of the browning reaction when fruit are cut or where internal disorders occur (Golan et al., 1977;Kahn, 1983). Phenolic acids generally are found in the cell vacuole or in special tissues, and are precursors of many other phytochemicals. The concentration of these compounds and the activity of the enzyme polyphenol oxidase (PPO) have long been known to be related to the process of browning. When membrane intergrity is lost, the phenols are released and oxidized to quinines by PPO (Torres at al., 1987). PPO includes the conversion of polyphenolic compounds in o-quinones, which in turn form melanins, responsible for the brown corolation (Kahn, 1983; Bower and Cutting, 1998). This process is influenced by different factors, such as concentration of H2O2 in cells, the structure of phenolic compounds and the rapidity of the main reaction (Amiot et al., 1997).