Phenolic compounds as beneficial phytochemicals in pomegranate (Punica granatum L.) peel: A review

Pomegranate peel (PoP), a juice byproduct often considered as a waste, comprises nearly around 30-40% portion of the fruit. Phenolic compounds (one class of bioactive phytochemicals) are primarily concentrated in the peel portion of pomegranate fruit. In PoP, the main phenolic compounds reported in the literature include flavonoids (anthocyanins such as pelargonidin, delphinidin, cyanidin along with their derivatives and anthoxanthins such as catechin, epicatechin and quercetin), tannins (ellagitannins and ellagic acid derivatives such as punicalagin, punicalin and pedunculagin) and phenolic acids (such as chlorogenic, caffeic, syringic, sinapic, p-coumaric, ferulic, ellagic, gallic and cinnamic acid). It is generally accepted that phenolic compounds can be more efficiently recovered from PoP by improving the extraction efficiency. The curative relevance of these compounds has been mainly assessed by in vitro experimentation. Therefore, conclusive clinical trials of the phenolic compounds present in PoP are essential for correct validation of their health benefits.