Evaluation of the Antiviral Activity of Cuscuta Extracts Against HSV-1, HSV-2 (ACV-Resistant Strain), HCoV229E and SARS-CoV-2
TL;DR
Investigation of the antiviral potential of extracts obtained from different parts of two species of C. campestris and C. epithymum found that the metabolic composition varies depending on the host plant, hypothesize that differences in the composition of the extracts lead to differences in antiviral activity.
Abstract
The toxicological risk and development of resistance associated with synthetic drugs and supplements can be reduced by focusing efforts on medicinal plants that are of interest in pharmacognostic research to find new drugs or templates for the development of new bioactive compounds. The parasitic plant Cuscuta spp. has significant pharmacological activity at the extract level, but there is limited data on the bioactivity of its chemical compounds. In the present study, we aimed to investigate the antiviral potential of extracts obtained from different parts of two species, C. campestris and C. epithymum. The two species clearly differ in their flavonoid profiles, which could also suggest different antiviral activities of the extracts. We used methanol and aqueous extracts, MDBK, VERO E6 clone 76 and BGM cell lines, HSV-1, HSV-2 strain DD (acyclovir-resistant), HCoV-229E and SARS-CoV-2, maximum tolerable concentration, the MTT test, the plaque-forming method and the HPLS-MS analysis. It was found that the metabolic composition varies depending on the host plant. We hypothesize that differences in the composition of the extracts lead to differences in antiviral activity. Some of the tested methanol extracts showed a pronounced inhibitory effect, both on replication and on extracellular virions, in relation to the ACV-resistant strain of HSV type 2 and SARS-CoV-2 in comparison with the other viral models used by us. The strongest antiviral effect was shown by the methanol extract of C. campestris with host Chenopodium spp. against SARS-CoV-2, as the virus inhibition was about 100%, and the virucidal effect showed a decrease in the viral titer by more than 2.5 lg. Based on the results obtained, we assume possible antagonistic interaction of individual metabolites in the total methanol extracts. Extract C3, applied at the maximum tolerable concentration and one level lower, inhibits SARS-CoV-2 about 100 percent. SARS-CoV-2-infected cells preserved mitochondrial activity and relatively preserved lysosomal activity; this is also the reason why the MTT test, as well as neutral red staining, is not applicable to this viral model propagated in the VERO E6 cell line.