**1. Introduction**

Cellular and tissue oxidative stress is a response to stimulation by increased reactive oxygen species (ROS) and free radicals in the body, resulting in dysregulation of the intracellular oxidative antioxidant system [1]. Cells can catalyze the superoxide anion produced in oxidative stress into H2O2, which is broken down into water and oxygen in one step by inducing superoxide dismutase (SOD), catalase, and glutathione peroxidase [2,3]. Oxidative stress could also disrupt intestinal homeostasis, which is a critical element in the development of intestinal damage. Stress can induce intestinal cells to produce large amounts of ROS metabolites, which affect the stability of intracellular nucleic acids, proteins, and lipids, increase apoptosis, inflict intestinal mucosal damage, and induce inflammatory bowel disease [4,5]. Many small intestinal epithelial cells exist on the surface of the intestine, and as a mediator of the internal and external environment of the intestine, the small intestinal epithelial cells are also part of the immune barrier that can defend the body against pathogens and other harmful substances [6–9]. Studies have shown that polysaccharides can scavenge ROS and enhance the antioxidant system to improve intestinal inflammation, therefore, it is relevant to find an antioxidant to protect the intestine from oxidative damage [10–13].

Yam is a plant from the *Dioscoreaceae* family. It grows in warm, low-altitude environments and is distributed throughout Asia, primarily in Korea, Japan, and China [14]. It contains polysaccharides, amino acids, fatty acids, trace elements, starch, protein, and other

**Citation:** Li, Z.; Xiao, W.; Xie, J.; Chen, Y.; Yu, Q.; Zhang, W.; Shen, M. Isolation, Characterization and Antioxidant Activity of Yam Polysaccharides. *Foods* **2022**, *11*, 800. https://doi.org/10.3390/ foods11060800

Academic Editors: Philippe Michaud and Lovedeep Kaur

Received: 23 December 2021 Accepted: 8 March 2022 Published: 10 March 2022

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components [15]. Polysaccharides extracted from yam have a variety of activities such as antioxidant, antitumor, immunomodulatory, and hypoglycemic. The monosaccharide composition of yam polysaccharides is complicated and caused by factors such as the growth conditions and different extraction methods. However, ribose is not found in the monosaccharide composition of most yam polysaccharides. Polysaccharides obtained from Chinese yams generally show good antioxidant activity in vitro, whereas glucose accounts for a large proportion of their monosaccharide composition. Based on the report of Liu et al., the molar ratios of glucose in the polysaccharides they obtained from Chinese yam all exceed 80% [16–20].

Over the past decade, antioxidant studies on yam polysaccharides have primarily focused on the free-radical scavenging ability in vitro. According to Zhu et al. [21], CYP has a strong antioxidant capacity and could effectively scavenge DPPH, ABTS+ and ·OH radicals, especially for DPPH radicals, whose scavenging ability is comparable to that of ascorbic acid (Vc). However, few studies have been conducted on the antioxidant activity of CYP at the cellular level. Despite salvia glycoproteins can increase the activity of antioxidant enzymes and reduce malondialdehyde (MDA) levels, the potential mechanism remains unknown. Therefore, it is meaningful to study this mechanism at the cellular level [22].

Despite the multiple biological activities of CYP, its structural features remain unclear and incomplete [23–25]. The structures of yams grown in different environments at different times are not quite the same, and their biological activities might still be different [26]. In the present study, we established a model of oxidative loss damage of cells by H2O2 and explored the protective effects of CYP on the oxidative damage of IEC-6 through cell-viability experiments and the levels of SOD and MDA levels.
