Gastroprotective effects of polysaccharides from purple sweet potato (Ipomoea batatas (L.) Lam) on an ethanol-induced gastric ulcer via regulating immunity and activating the PI3K/Akt/Rheb/mTOR pathway.

The study aimed to investigate the alleviation of an ethanol-induced gastric ulcer in mice by apolysaccharide (PSP) from purple sweet potato (Ipomoea batatas (L.) Lam) and explore the mechanism. The anti-ulcer activity was determined by histopathological evaluation, total gastric acidity, pepsin activity, gastric ulcer index and gastric ulcer inhibition rate. The expression levels of inflammatory factors were detected using ELISA. A special protein meter was used to detect the content of immunoglobulin lgM, immunoglobulin lgG, and complements C3 and C4 in the serum of mice. The expression of CD4+/CD8+ lymphocyte subsets of mice was detected using flow cytometry. Western blot analysis was used to examine the effect of PSP on the PI3K/Akt/Rheb/mTOR pathway. The results showed that PSP could effectively reduce the total gastric acidity, pepsin activity, and the index and inhibition rate of gastric ulcers. At the same time, PSP could significantly increase the levels of immunoglobulins (lgG and lgM) and complements (C3 and C4). It could also increase the activity of peritoneal macrophages in mice and the expression of CD4+/CD8+ in the spleen. ELISA analysis showed that the contents of TNF-α, IL-1ß and IL-6 were significantly decreased and the content of IL-10 was significantly increased in the PSP group. The western blot analysis showed that PSP could upregulate the relative protein expressions of MUC5AC, PI3K, p-Akt, Rheb and mTOR. These results indicate that PSP can activate the PI3K/Akt/Rheb/mTOR signaling pathway to improve the immunity of mice and maintain the balance of the immune system, thereby protecting the gastric mucosa and improving stress gastric ulcers.

Optimization of Extraction Process and Activity of Angiotensin-Converting Enzyme (ACE) Inhibitory Peptide from Walnut Meal.

In order to further realize the resource reuse of walnut meal after oil extraction, walnut meal was used as raw material to prepare polypeptide, and its angiotensin-converting enzyme (ACE) inhibitory activity was investigated. The ACE inhibitory peptides were prepared from walnut meal protein by alkaline solution and acid precipitation. The hydrolysis degree and ACE inhibition rate were used as indexes to optimize the preparation process by single-factor experiment and response surface method. The components with the highest ACE activity were screened by ultrafiltration, and their antioxidant activities were evaluated in vitro. The effect of gastrointestinal digestion on the stability of walnut peptide was analyzed by measuring molecular weight and ACE inhibition rate. The results showed that the optimal extraction conditions were pH 9.10, hydrolysis temperature 54.50 °C, and hydrolysis time 136 min. The ACE inhibition rate of walnut meal hydrolysate (WMH) prepared under these conditions was 63.93% ± 0.43%. Under the above conditions, the fraction less than 3 kDa showed the highest ACE inhibitory activity among the ACE inhibitory peptides separated by ultrafiltration. The IC50 value of scavenging ·OH free radical was 1.156 mg/mL, the IC50 value of scavenging DPPH free radical was 0.25 mg/mL, and the IC50 value of scavenging O2- was 3.026 mg/mL, showing a strong total reducing ability. After simulated gastrointestinal digestion in vitro, the ACE inhibitory rate of walnut peptide decreased significantly, but it still maintained over 90% ACE inhibitory activity. This study provides a reference for the application of low-molecular-weight walnut peptide as a potential antioxidant and ACE inhibitor.