Comparative Analyses of Few West Turkish Varieties of Pomegranate (Punica granatum L.) Peels for Phenolic Content Using Liquid Chromatography

Abstract

In this work, the amounts of phenolic compounds in the peels of four different pomegranate varieties grown in Özdere-İzmir, Turkey were investigated for the first time. Three different extraction processes namely reflux, ultrasonic bath and mixing, were carried out with dry and fresh pomegranate peels for two different periods of 4 and 12 h. The best results for ellagic acid, hesperidin, and quercetin, except resveratrol, were observed in refluxing extraction in MeOH. It is seen that the amounts of ellagic acid obtained from the dry samples are quite good in shorter extraction time (4-h) as 2778, 3376, 5024 and 3115 µg/g, when compared to fresh samples where reduced amounts were obtained as 973, 2046, 3232 and 1822 µg/g. Similarly, the highest ellagic acid quantities were observed in dry and fresh samples as named of İzmir 8; 2624 µg/g and 8761 µg/g, respectively by using HPLC-DAD for longer extraction time (12-h) which was found to negatively affect the phenolics for fresh samples. In fresh samples, extraction is rapid and long heating causes deterioration. As expected, the amount of ellagic acid was higher in the dry ones. The flavonoids hesperidin and quercetin were detected in quite well amounts for most of the samples, also hesperidin was in high as about 85.5 and 73.3 µg/g in one of the samples. Fifteen different phenolics such as ellagic acid, hesperidin, quercetin, resveratrol, catechin, epicatechin, gallocatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, cyanidin, delphinidin, malvidin, myricetin, caffeic acid, caftaric acid, p-coumaric acid, gallic acid and ferulic acid were investigated. The antioxidant activity and total phenolic content analyses were also conducted in the methanolic supernatant extracts. DPPH inhibitions of all extracts varied from 47.22% to 93.83% at 4-h and from 36.88% to 94.96% at 12-hour extractions. Furthermore, ANOVA analyzes for ellagic acid and some catechin derivatives was conducted.

Keywords:

• Antioxidant effect
• HPLC-DAD
• phenolics
• pomegranate peel
• UHPLC-MS/MS

Acknowledgements

We would like to thank S. Şentürk, half director of Redox Lab, and T. Kaymaz, an academic staff member of University of Suleyman Demirel, for their valuable supports and UHPLC-MS/MS analysis.

Disclosure statement

The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.