Autoxidation Products of the Methanolic Extract of the Leaves of Combretum micranthum Exert Antiviral Activity against Tomato Brown Rugose Fruit Virus (ToBRFV).

Tomato brown rugose fruit virus (ToBRFV) is a new damaging plant virus of great interest from both an economical and research point of view. ToBRFV is transmitted by contact, remains infective for months, and to-date, no resistant cultivars have been developed. Due to the relevance of this virus, new effective, sustainable, and operator-safe antiviral agents are needed. Thus, 4-hydroxybenzoic acid was identified as the main product of the alkaline autoxidation at high temperature of the methanolic extract of the leaves of C. micranthum, known for antiviral activity. The autoxidized extract and 4-hydroxybenzoic acid were assayed in in vitro experiments, in combination with a mechanical inoculation test of tomato plants. Catechinic acid, a common product of rearrangement of catechins in hot alkaline solution, was also tested. Degradation of the viral particles, evidenced by the absence of detectable ToBRFV RNA and the loss of virus infectivity, as a possible consequence of disassembly of the virus coat protein (CP), were shown. Homology modeling was then applied to prepare the protein model of ToBRFV CP, and its structure was optimized. Molecular docking simulation showed the interactions of the two compounds, with the amino acid residues responsible for CP-CP interactions. Catechinic acid showed the best binding energy value in comparison with ribavirin, an anti-tobamovirus agent.

Antiphytoviral toxins of Actinidia chinensis root bark (ACRB) extract: laboratory and semi-field trials.

BACKGROUND: Actinidia chinensis Planch, which is distributed only in China, has been used to treat hepatitis and cancer. The objective of the present work was to identify the antiviral active ingredient of A. chinensis root bark (ACRB). RESULTS: Bioassay-guided isolation of the most active fraction, the EtOAc extract, led to the identification of seven compounds, (+)-catechins-7-phytol (1), 5-methoxy-coumarin-7-ß-D-glycosidase (2), (+)-catechins (3), fupenzic acid (4), spathodic acid-28-O-ß-D-glucopyranoside (5), 3-oxo-9, 12-diene-30-oic acid (6), and 3-ß-(2-carboxy benzoyloxy) oleanolic acid (7). Of these, 5-methoxy-coumarin-7-ß-D-glycosidase (2) possessed the highest antiviral activity, followed by spathodic acid-28-O-ß-D-glucopyranoside (5). Thus, compounds 2 and 5 were the main active constituents, with potential for further development as biological antiviral agents. CONCLUSION: The results suggest that ACRB possesses great potential value for development of an antiviral agent to control phytoviral diseases. © 2018 Society of Chemical Industry.

Inhibitory Components from Glycosmis stenocarpa on Pepper Mild Mottle Virus.

The goal of this study was to identify a source of natural plant compounds with inhibitory activity against pepper mild mottle virus (PMMoV). We showed, using a half-leaf assay, that murrayafoline-A (1) and isomahanine (2) isolated from the aerial parts of Glycosmis stenocarpa have inhibitory activity against PMMoV through curative, inactivation, and protection effects. Using a leaf-disk assay, we confirmed that 2 inhibited virus replication in Nicotiana benthamiana. Using electron microscopy, we found that a mixture of the virus with 2 resulted in damage to the rod-shaped virus.