Novel galloylated catechin-menthofuran conjugate derived from persimmon tannin with potential anti-ulcer activity

A new method for acid-catalyzed degradation of Persimmon tannin (PT) was established using menthofuran as a nucleophile. Four new flavan-3-ol conjugates were obtained by reacting menthofuran with PT at 60 °C in 0.2M HCl-ethanol solution for 90 min by single factor experiment, with the yield of the main degradation products epigallocatechin gallate-menthofuran (EGCG-MF) and epicatechin gallate-menthofuran (ECG-MF) being 246 mg/g and 77 mg/g, respectively. Animal experiments proved that, compared to the untreated mice, the two main degradation products showed equivalent anti-ulcer activity as positive drug cimetidine, with inhibition rates of 55.32 % and 53.90 % for EGCG-MF and ECG-MF, respectively. H&E staining and PAS staining showed that the two substances had a protective effect on the gastric mucosa. They exerted the anti-ulcer activity by enhancing the expression of tight junction proteins Occludin and Zonula occludens-1 (ZO-1). The recovery rates of the two products for the two proteins were 73.89 %, 80.23 % and 68.72 %,88.44 %, respectively. In addition, by measuring the levels of oxidative stress markers such as MDA, SOD, GSH, as well as inflammatory factors TNF-α, IL-6, IL-10 in mice, it was found that two degradation products could treat gastric ulcers by reducing the levels of oxidative stress and inflammation. This work provided new application ideas for the application of proanthocyanidins in functional foods and medical fields.