# Structural Elucidation of a Novel Pectic Polysaccharide from Zizyphus jujuba cv. Muzao, a Potential Natural Stabiliser

## TL;DR

This paper identifies a new pectin from a type of jujube that could be used as a natural stabilizer in acidic fruit and vegetable juices.

## Contribution

The study isolates and structurally characterizes a novel pectic polysaccharide from Zizyphus jujuba cv. Muzao suitable for acidic environments.

## Key findings

- ZMP2 contains high levels of galacturonic and glucuronic acids, indicating it is likely pectin.
- The primary structure of ZMP2 was determined using NMR and other spectroscopic techniques.
- ZMP2 has a main chain with specific glycosidic bonds and branching patterns.

## Abstract

The pH of fruit and vegetable juices is usually around 4.0. To adapt to the pH of fruit and vegetable juices, we developed a highly branched pectin as a natural stabiliser, whose polarity is well suited to conditions under weakly acidic conditions. The pectin content of jujube is high (about 2.0%), in which the polysaccharide content of Muzao (2.0–4.8%) is generally higher than the average value of the jujube. To separate the weak polar pectin in jujube, we extracted the crude polysaccharide (ZMP) with 4 times the volume of alcohol. Then we used Diethylaminoethyl (DEAE) cellulose (DEAE-52) ion-exchange chromatography to separate ZMP, and selected the fraction eluted with 0.2 M NaCl for gel purification to obtain ZMP2. After the hydrolysis of ZMP2 with TFA, four fractions, namely ZMP2n5, ZMP2y5, ZMP2n1, and ZMP2y1, were obtained. The purity, molecular weight, and monosaccharide composition of the above four fractions were determined. It was found that each fraction of ZMP2 contained large amounts of galacturonic acid (GalA) and glucuronic acid (GlcA), indicating that ZMP2 was most likely pectin, making it the natural, polar stabiliser we sought. To further determine the primary structure of ZMP2, we also performed FT-IR spectroscopy; methylation; one-dimensional mapping, including Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR) and Distortionless Enhancement by Polarization Transfer 135 (DEPT 135); and two-dimensional mapping, including Correlation Spectroscopy (1H-1H COSY), Heteronuclear Single Quantum Coherence (HSQC), Heteronuclear Multiple-Bond Correlation (HMBC), and Nuclear Overhauser Effect Spectroscopy (NOESY). In summary, the primary structure of ZMP2 should be as follows: the main chain is connected as →4)-α-D-GalAp-(1→3)-β-D-Galp-(1→, while the end glycosidic bonds of α-D-Galp-(1→ and α-L-Araf-(1→5)-α-L-Araf-(1→ are attached to the main chain by O-3 and O-6 bonds from →3,4)-α-D-GalAp-(1→ and →3,6)-β-D-GalAp-(1→, respectively.