From China:Xinjiang Institute of Physics and Chemistry has made progress in the study of polyphenols in pomegranate peel

Pomegranate is widely grown in Xinjiang as a nutrient-rich fruit, and the non-edible portion of pomegranate skin accounts for about half of the total fruit weight. In addition to direct consumption, the most important industrial processing way of pomegranate is to press juice, resulting in a large amount of pomegranate skin waste, not only pollution to the environment, but also a serious waste of resources. Studies have shown that pomegranate peel has antioxidant, antibacterial, anti-tumor, anti-inflammatory and other biological activities. Polyphenols are important active components in pomegranate peel, and are the first choice raw materials to develop pomegranate biological activity, which has great potential application value.

Pomegranate peel polyphenols have strong polarity, poor solubility, and are easy to be oxidized or decomposed. The content of other polyphenols in pomegranate peel is low except garnet glycoside, so the separation and purification of pomegranate peel polyphenols is a very challenging task. In addition, there is a large amount of quaternary carbon in the structure of pomegranate peel polyphenols, which has a low signal in 2D nuclear magnetic resonance spectroscopy (2D-NMR), which brings great difficulty to the structure identification. Therefore, in recent years, the research on pomegranate peel mainly focuses on the qualitative analysis of its chemical constituents, but less on the isolation and structural characterization of monomeric compounds.

Aji Ekbel Issa, a researcher at the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, conducted a study on the isolation, purification, structural identification and biological activity of polyphenols from pomegranate peel in Xinjiang. The team isolated and purified 10 polyphenols from pomegranate peels using a combination of column chromatography, cryogenic chromatography and high phase liquid chromatography. The structures of these compounds were determined by high resolution mass spectrometry, one – and two-dimensional nuclear magnetic resonance spectroscopy. Three of them were new compounds containing a hexahydroxydiphenoyl (HHDP). A 2,3,4, 5-tetra-substituted benzoate group and a 1,4, 6-trisubstituted glucose group.

To gain a preliminary understanding of the biological activities of these polyphenols, antibacterial, antioxidant and antitumor activities were measured in vitro. The results showed that six compounds showed significant scavenging activity against 1, 1-diphenyl 2-picrylhydrazyl radical 2, 2-diphenyl 1-(2,4, 6-Trinitrophenyl)hydrazyl, DPPH】 ability; The two compounds had certain antibacterial activities against Candida albicans. One compound had certain antibacterial activity against Candida albicans and Escherichia coli. The four compounds had weak inhibitory effect on the proliferation of human cervical cancer Hela cells.

This study not only enriched the chemical composition and biological research results of pomegranate peel, but also further confirmed the functional value of pomegranate peel extract and the potential application value of pomegranate peel extract as functional food additives.

The study was published in the Journal of Agricultural and Food Chemistry. The research work was supported by the “Light of the West” talent training program of Chinese Academy of Sciences and the Technical Innovation Project of instrument and equipment Function Development of Chinese Academy of Sciences.

The paper links

The chemical structure of compounds 1-3 is related to the main 1H-1H COSY and HMBC

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