Phlorotannins: A review of extraction methods, structural characteristics, bioactivities, bioavailability, and future trends

Abstract Background In recent years, phlorotannins, a class of polyphenols with strong biological properties derived from brown algae and not present in terrestrial organisms, have attracted widespread attention due to their broad application prospects. Scope and approach This review focuses on the extraction methods of phlorotannins and summarizes the structural characterization of phlorotannins with different molecular weight as well as their main biological properties in vitro and in vivo, highlighting future trends and applications of these compounds. Key findings and conclusions There are multiple extraction methods to obtain phlorotannins, being some of the most promising ultrasonic assisted extraction (UAE), microwave assisted extraction (MAE) and enzyme assisted extraction (EAE). However, there is no standard unified extraction method for phlorotannins, and there is still potential for development and optimization of the application of these technologies. In addition, methods involving the combination of multiple extraction techniques should be further explored for phlorotannins' extraction. Moreover, the structural characterization of phlorotannins and its potential bioactivities, such as anti-diabetic, anti-cancer, and anti-inflammatory effects, still need to be further explored. The structural change of phlorotannins with high degree of polymerization may contribute to the increase of its bioactivity. Phlorotannins research trends include more efficient and optimized extraction methods, specific bioactivity of single phlorotannins, relationship between structure and its biological activity, research on drug delivery systems, and development of functional foods and nutraceutical.