## 3 Avocado's Composition in Nutrients and Bioactives
### Avocado Bioactive Compounds
#### 3.2.1 Phenolic Content
Phenolic compounds exhibit properties that allow them to combat free radicals and, therefore, decrease degenerative diseases associated with oxidative stress, such as cardiovascular and neurological disorders or UV-induced skin aging. They are additionally acknowledged for their antifungal and antibacterial effects, especially against Gram-positive bacterial strains [60; 62; 64]. As a result, phenolic compounds are recognized as the primary kind of antioxidants that can neutralize free radicals by single electron transfer (SET) or hydrogen atom transfer (HAT). According to published research, the amount and arrangement of hydroxyl groups in phenolics compounds places a significant impact on avocado's antioxidant activity [62]. At the same time, avocado industries face a huge issue in managing the large amount of generated waste, which consists of seeds and peels, representing 21-30% of the total raw material. These by-products are knowingly rich in polyphenols that can be utilized for diverse biological activities mainly because of their antibacterial, antimicrobial, anti-inflammatory, anticarcinogenic, epigenetic, and chemo-preventive properties [63]. In avocado's by-product extracts, the total phenolic compounds that have been identified, as shown in Table 2, range from 4.250 to 66.1 mg g\({}^{-1}\). Some of the phenolic compounds identified in avocado's by-product extracts are epicatechin, procyanidin B2, 5-O-caffeoyl-quinic acid, procyanidin B trimmers, kaempfer O-glucosyl rhamnoside, myricetin 3-rhammoside, kaempfer, gallic acid, chlorogenic acid, p-hydrobenzoic acid, caffe acid, benzoic acid, catechhin, epigallocatechin, rutinoside-3-O-quercetin, glycoside-3-O-kaempfer, and quercetin [66]. Remarkably, the peel and seed of avocados contain higher concentrations of these phenolic compounds compared to the pulp, with the avocado peel extracts exceeding the phenolic quantities of the seed extracts. More particularly, seeds, except for their high starch content, also have a high polyphenol content, causing a bitter taste and harm if consumed in excess. Fruit peels, on the contrary, are valued for their profusion of polyphenols and antioxidants, which function as barriers to prevent oxidative stress caused by high temperatures and sunshine. [65]. Several studies in different varieties of _P. americana_ leaf extracts have demonstrated strong antioxidant activity, while purified leaf extracts have a concentration-dependent antibacterial effect. Plant phenolics are primarily attached to plant cell walls, and their effectiveness depends on both availability and chemical composition. Fermentative bacteria in the human gut convert these dietary phenolics and, hence, improve absorption and regulate health-promoting properties [64]. Moreover, limited studies suggest that avocado by-products could produce phenolic-rich extracts with antiproliferative effects, which possess valuable prospects for cancer prevention and treatment. The peel of avocado extracts have been shown to induce apoptosis in MDA\(-\)MB\(-\)231 cells through promoting the activation of caspase 3 and its target protein PARP [62]. Consequently, these residues provide a low-cost source of phenolic acids and flavonoids via extracts that have substantial functional potential [62]. In avocado peel extracts, seed coat, and seed, 72 district compounds were identified. Peel extract have the greatest amount of compound variety, with 69 phenolics noted, followed by seed coat and seed extracts, both with 58 compounds. Among the seed coat and seed extracts, the first consists of higher amounts of trans-cinnamic acid derivatives. In the peel extract, epicatechin and type B procyanidin dimers are the prevalent flavonoids, while seed coat extracts consist of type B procyanidin dimers and trimmers, along with type A procyanidin dimers and trimmers. Sakuranetin and luteolin are the only flavonoidsdetected in greater quantities in seed extracts than in peel and seed coat extracts. In contrast, pensentide, a terpene, is detected in all the parts of avocado's by-products.