## 4 Health-Promoting Effects of Avocado and Its Bioactives  
### Antioxidant Activity  
Avocados are rich in antioxidative chemicals, which have scientifically been proven to have a positive impact on overall health and well-being. Remarkably, abundant polyphenol content--especially in terms of phenolic and tannin compounds--has a strong correlation with avocados' antioxidant function. These polyphenols increase avocados' total antioxidant activity, which raises their nutritional content and may hold positive effects on health. Knowing this relationship can help people make educated food decisions that promote general health and well-being, and avocado has been in the spotlight of research over the past few years [47]. A series of mechanisms underline polyphenols' antioxidant qualities. In detail, the phenolic hydroxyl group can donate one hydrogen atom or an electron to the reactive oxygen species (ROS), which results in their decomposition. Also, the activity and synthesis of enzymes that are essential for neutralizing oxidants can be controlled from polyphenols. The main oxidase enzymes that are responsible for this are SOD1 and SOD2 because of their ability to convert superoxide into hydrogen peroxide. Afterward, CAT or GSH-Px deactivates hydrogen peroxide to produce water and oxygen. Moreover, in the Nrf pathway, Nrf2 is a transcriptional factor that regulates the expression of detoxifying enzymes like SOD, GPx1, NQO1, GST, and HO-1 and is in turn regulated by polyphenols via their binding to antioxidant response elements (AREs) in the promoter regions of enzyme genes. This process increases the antioxidant activity of cells. Resveratrol has the ability to break down the Nrf2-Keap complex in the cytosol, which permits Nrf2 to go into the nucleus and attach itself to the 5\({}^{\prime}\)-promoter region of NQO1 that contains AREs, thus activating transcription [95].  
The quantification of antioxidant activity (AA) can be achieved with a series of tests. The DPPH free radical is a long-lived organic nitrogen radical with a deep purple color, while when a DPPH solution is mixed with an antioxidant, its color turns from purple to yellow of the corresponding hydrazine, and, thus, the reducing ability of antioxidants toward DPPH is usually evaluated by monitoring the decrease in its absorbance at 515-528 nm, with the results usually expressed as half the maximum inhibitory concentration (IC50 value) or as a % scavenging of DPPH\({}^{\bullet}\) at a fixed antioxidant concentration for all the tested compounds, or even as Trolox equivalent antioxidant capacity (TEAC) after normalizing with the respective Trolox equivalent IC50 value [96]. Many studies have utilized the in vitro assay to investigate and validate the antioxidant properties of avocado fruit [18; 46; 47; 64; 71; 79; 97; 98; 99; 100; 101; 102; 103; 104]. Moreover, the reduction of ferric-tripyridtriazine to a unique blue ferrous-tripyridtriazine complex that displays a noticeable absorption peak at 593 nm is a common step in the FRAP assay that is utilized to evaluate antioxidant activity [105]. This assay has proven to be useful in determining the antioxidant capacity of different avocado constituents [18; 46; 47; 63; 64; 71; 98; 99; 100; 102]. In order to validate the statements made about avocados' antioxidant activity (AA), further tests such as ABTS ([18; 46; 47; 63; 100; 101]), RPA ([46; 47; 99]), TAC ([46; 47]), OH--RSA ([46; 47; 99]), FICA ([46; 47]) were conducted. These studies contributed to our full understanding of the health benefits of avocados by shedding more light on the antioxidant potential of various avocado segments, as displayed in Table 2.