Diverse Phytochemicals and Bioactivities in the Ancient Fruit and Modern Functional Food Pomegranate (Punica granatum)

Abstract

Having served as a symbolic fruit since ancient times, pomegranate (Punica granatum) has also gained considerable recognition as a functional food in the modern era. A large body of literature has linked pomegranate polyphenols, particularly anthocyanins (ATs) and hydrolyzable tannins (HTs), to the health-promoting activities of pomegranate juice and fruit extracts. However, it remains unclear as to how, and to what extent, the numerous phytochemicals in pomegranate may interact and exert cooperative activities in humans. In this review, we examine the structural and analytical information of the diverse phytochemicals that have been identified in different pomegranate tissues, to establish a knowledge base for characterization of metabolite profiles, discovery of novel phytochemicals, and investigation of phytochemical interactions in pomegranate. We also assess recent findings on the function and molecular mechanism of ATs as well as urolithins, the intestinal microbial derivatives of pomegranate HTs, on human nutrition and health. A better understanding of the structural diversity of pomegranate phytochemicals as well as their bioconversions and bioactivities in humans will facilitate the interrogation of their synergistic/antagonistic interactions and accelerate their applications in dietary-based cancer chemoprevention and treatment in the future.

Keywords: Punica granatum; anthocyanin; ellagic acid; ellagitannin; functional food; hydrolyzable tannin; polyphenol; pomegranate; urolithin.

Figure 1

Pomegranate ellagitannin-derived metabolites. (A) Punicalagin (a pomegranate ellagitannin) is hydrolyzed to hexahydroxydiphenic acid, which is lactonized to yield ellagic acid; (B) Chemical structures of representative urolithins, the microfloral transformation products of ellagic acid.