Chemical Constituents of the Seeds of Aesculus turbinata and Their PEDV Inhibitory Activity

Abstract

Porcine epidemic diarrhea virus (PEDV) causes severe diarrhea and high fatality of piglets, influencing the swine industry. Japanese horse chestnut (seed of Aesculus turbinata) contains many saponin mixtures, called escins, and has been used for a long time as a traditional medicinal plant. Structure-activity relationship (SAR) studies on escins have revealed that acylations at C-21 and C-22 with angeloyl or tigoloyl groups were important for their cytotoxic effects. However, the strong cytotoxicity of escins makes them hard to utilize for other diseases and to develop as nutraceuticals. In this research, we investigated whether escin derivatives 1-7 (including new compounds 2, 3, 5 and 6), without the angeloyl or tigloyl groups and with modified glycosidic linkages by hydrolysis, have PEDV inhibitory effects with less cytotoxicity than the major compounds 8-10 isolated from the extract. Compounds 1-7 had no cytotoxicity at 20 μM on VERO cells, while compounds 8-10 showed strong cytotoxicity at similar concentrations, and also had moderate inhibitory activities on PEDV. Our results suggest that escin derivatives, which were prepared by two-step reactions, showed strong inhibitory activities on PEDV replication with less cytotoxicity. These studies proposed a method to utilize Japanese horse chestnut for treating PEDV with less cytotoxic effects, and to increase the diversity of its bioactive compounds.