Plant-derived compounds: A potential source of drugs against Tobacco mosaic virus

Tobacco mosaic virus (TMV) is an important plant virus that led to significant losses in the crops worldwide. In this study, the antiviral activities of Ursolic Acid (UA) and 4-methoxycoumarin against TMV and their underlying mechanisms were initially investigated for the first time. The results demonstrated that the antiviral effects of UA and 4-methoxycoumarin were as effective as those of the commercial agent lentinan, in either the protective effect, inactivation effect or curative effect. In addition, both plant-derived compounds could induce the resistance responses of tobacco plants against TMV, showing increased antioxidant enzyme activities (SOD and POD) and H₂O₂ accumulation in tobacco leaves after treatment with UA or 4-methoxycoumarin, along with highly expressed regulatory and defence genes in the salicylic acid signaling pathway. Meanwhile, electrolyte leakage and malondialdehyde experiments indicated that these effects did not result in phytotoxicity or damage to the leaf plasma membrane of tobacco plants. Collectively, the results demonstrate that UA and 4-methoxycoumarin have potential as eco-friendly and safe strategies to control TMV in the future.