Characteristics and Mode of Action of a Virus Inhibitor from Cuscuta reflexa Plants

Abstract

Summary The aqueous extract from the filaments of Cuscuta reflexa has shown a broad spectrum and highly significant antiviral activity. Treatment of the inhibitor on the two basal leaves of several hypersentitive hosts, prior to inoculation of viruses (isometric and anisometric), resulted in gradual increase in virus inhibition with the increase in time interval between treatment and virus challenge up to 24 hrs., thereafter the resistance of the host plants gradually decreased. In post inoculation treatments, it was effective only when applied up to 2 hrs. following virus inoculation. Along with the high degree of local inhibitory response, systemic acquired resistance (resistance at non-treated sites) was also observed in different host—virus combinations. The resistance induced (both localized and systemic) by C. reflexa inhibitor was significantly reversed by the application of actinomycin D up to 6 hrs. after treatment. AD had no effect when applied 24 hrs. after treatment with the inhibitor. The maximum inhibition was achieved by the inhibitor from the filaments of mature plants of C. reflexa, parasitizing on Zizyphus jujuba. The resistance induced by C. reflexa inhibitor was sensitive to high temperature. Extract from C. reflexa filaments was inhibitory up to a dilution of 1: 100, inactivated at 70 °C, and survived at room temperature for 12 days. The inhibitory material in crude extract was non-dialyzable, not sedimented at 120,000 g for 120 min, precipitated by a saturated solution of ammonium sulphate or ethanol, inactivated by trichloroacetic acid, adsorbed on animal charcoal, wood charcoal or celite, active at pH 10, and insoluble in diethyl ether, petroleum ether, chloroform or benzene.