Antifungal activity of pregnane glycosides isolated from Periploca sepium root barks against various phytopathogenic fungi

No doubt that studying the secondary metabolites produced by plants can lead to the detection of new pesticides. In this study, we followed the bioassay-guided method to isolate active ingredients from Periploca sepium root barks (PSRB) and verified their antifungal activity against seven phytopathogenic fungi in vitro. A total of six pregnane glycosides were isolated and identified as periplocoside A (PSA), periplocoside D (PSD), periplocoside E (PSE), periplocoside F (PSF), periplocoside N (PSN) and periploside W (PSW). Bioassay results revealed that PSW exhibited highly significant antifungal activity against Valsa mali and Fusarium graminearum with EC50 values of 26.50 mg/L and 93.94 mg/L, respectively. In controlling apple Valsa canker, PSW (1000 mg/L) exhibited significantly higher protective activity with 85.40% than that efficacy with 64.62% obtained by carbendazim (200 mg/L). Whereas there is no significant difference between both of them in the curative efficacy with 71.32% and 69.70%, respectively. In conclusion, our study recommended the pregnane glycosides from PSRB as a new class of fungicides or fungicide lead compounds not only because of their potential antifungal activity, but also because of their safety for human beings, mammals and non-target organisms.