Effects of Season, Variety, and Processing Method on Ellagic Acid Content in Pomegranate Leaves

Ellagic acid (EA) has aroused great interest worldwide owing to its antioxidant, anti-inflammatory, and anticarcinogenetic properties. The EA content in pomegranate leaf was measured in this study using high performance liquid chromatography to investigate the effects of season, variety, and processing method on the EA level. The results show that the EA content in 11 varieties of pomegranate from the Zaozhuang region in China range from 1.30 mg · g^–1 to 6.46 mg · g^–1 of dry weight in five consecutive seasons from June to October. An analysis of variance (ANOVA) shows that the EA content is significantly dependent on the season (p<0.05). The EA content increases significantly during the growing season to the highest level in September and October. The effect of the leaf variety on the EA content is less significant than the season. The processing methods have different effects on the EA content. Soaking for 24 hours slightly increases the EA content (p<0.05). Heating at 80℃ or 100℃ for 1 h after soaking has little influence on the EA content, while slow-fired cooking at high temperature significantly elevates the EA content (p<0.05). To improve quality and stability, several parameters such as leaf collection time, slow-fired cooking, and cooking time should be strictly controlled during the processing of pomegranate leaf tea and its extract.