Porcine epidemic diarrhea virus infection: inhibition by polysaccharide from Ginkgo biloba exocarp and mode of its action.

Porcine epidemic diarrhea virus (PEDV) is the predominant cause of severe entero-pathogenic diarrhea in swine. Until now there is no recorded clinically effective antiviral chemotherapeutic agent for treatment of diseases caused by PEDV. This study aimed to investigate in vitro anti-PEDV effect of polysaccharide from Ginkgo biloba exocarp and mode of its action. The polysaccharide exhibited potent antiviral activity against PEDV reducing the formation of a visible CPE [a 50% inhibitory concentration (IC50)=1.7±1.3µg/mL], compared to positive control, ribavirin and it did not show cytotoxicity at 100µg/mL [a 50% cytotoxicity concentration (CC50)=100µg/mL]. Polysaccharide also showed effective inhibitory effects when added at the viral attachment and entry steps. Moreover, polysaccharide effectively inactivated PEDV infection in time-, dose- and temperature-dependent manners. Overall, this research revealed that polysaccharide could inhibit PEDV infection, and that polysaccharide may be involved in PEDV-Vero cell interactions, as the virus attachment and entry to the Vero cells was hindered by the polysaccharide. Therefore, polysaccharide possessing effective inhibitory effect on viral attachment and entry steps of PEDV life cycle is a good candidate for development of antivirals.

Isolation of betulinic acid, its methyl ester and guaiane sesquiterpenoids with protein tyrosine phosphatase 1B inhibitory activity from the roots of Saussurea lappa C.B.Clarke.

Activity-guided fractionation of a MeOH extract of the roots of Saussurea lappa C.B.Clarke (Compositae), using an in vitro protein tyrosine phosphatase 1B (PTP1B) inhibition assay, led to the isolation of four active constituents: betulinic acid (1), betulinic acid methyl ester (2), mokko lactone (3) and dehydrocostuslactone (4), along with nine inactive compounds. Our findings indicate that betulinic acid (1) and its methyl ester 2, as well as the two guaiane sesquiterpenoids 3 and 4 are potential lead moieties for the development of new PTP1B inhibitors.