Preparation method and stability of ellagic acid-rich pomegranate fruit peel extract

Abstract

A simple one-step purification using liquid–liquid extraction for preparing pomegranate peel extract rich in ellagic acid has been demonstrated. The method involved partitioning of the 10% v/v water in methanol extract of pomegranate peel between ethyl acetate and 2% aqueous acetic acid. This method was capable of increasing the ellagic acid content of the extract from 7.06% to 13.63% w/w. Moreover, the antioxidant activity of the extract evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay was also increased (ED₅₀ from 38.21 to 14.91 μg/mL). Stability evaluations of the ellagic acid-rich pomegranate peel extract in several conditions through a period of four months found that the extracts were stable either kept under light or protected from light. The extracts were also stable under 4° ± 2°C, 30° ± 2°C and accelerated conditions at 45°C with 75% relative humidity. However, study on the effect of pH on stability of the extract in the form of solution revealed that the extract was not stable in all tested pH (5.5, 7 and 8). These results indicated that the ellagic acid-rich pomegranate peel extract was stable when it was kept as dried powder, but it was not stable in any aqueous solution.

Keywords::

• Punica granatum
• pomegranate
• ellagic acid
• stability
• antioxidant

Acknowledgements

The authors wish to thank the National Research Council of Thailand and the Graduate School, Prince of Songkla University, for support in the form of a research grant.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.