A review on the extraction of polyphenols from pomegranate peel for punicalagin purification: techniques, applications, and future prospects

Pomegranate peel is rich in polyphenols with punicalagin as the dominant compound but is always regarded as agricultural waste. This review focuses on the extraction of polyphenols as well as the purification, food industry applications and health effects of punicalagin. Considering polyphenol extraction, solvent extraction is the most commonly used method because it offers the highest total phenolic content; however, it is time consuming and energy intensive. Therefore, advanced methods are used to enhance its extraction efficiency, such as enzyme-assisted solvent extraction, resulting in the highest extraction yield. As for the purification of punicalagin from polyphenols, liquid chromatography is the most widely used method, and the highest purity is achieved with semi-high-pressure liquid chromatography (HPLC). Medium-pressure liquid chromatography (MPLC) and high-speed countercurrent chromatography (HSCCC) have similar effects, but relatively fewer studies have adopted these two methods. Besides, punicalagin has outstanding antioxidant properties and can thus be added to functional foods to extend their shelf life. Moreover, it shows great antibacterial effects on drug-resistant pathogens. Its anti-inflammatory potential is governed by its ability to treat infection and hyperimmune-related disorders. This work provides a comprehensive review of methods for extracting and purifying valuable compounds from pomegranate peel, particularly punicalagin, and highlights its potential applications in functional foods and health therapies.