• 7-methoxycryptopleurine;
  • antiviral activity;
  • phenanthroquinolizidine alkaloids;
  • salification;
  • structure–activity relationships;
  • tobacco mosaic virus

A series of 7-methoxycryptopleurine derivatives 223 were prepared and evaluated for their antiviral activity against tobacco mosaic virus (TMV) for the first time. The bioassay results showed that most of these compounds exhibited excellent in vivo anti-TMV activity, of which 7-methoxycryptopleurine salt derivatives 16, 19, and 23 displayed significantly higher activity than 7-methoxycryptopleurine (1) and commercial ribavirin and ningnanmycin. Salification, the most commonly employed method for modifying physical-chemical properties, did significantly increase antiviral activity, and different salt forms displayed different antiviral effect. This study provides fundamental support for development and optimization of phenanthroquinolizidine alkaloids as potential inhibitors of plant virus.