Which chemical compounds do Gentianales plants produce to discourage herbivores?

To discourage herbivores, plants in the Gentianales order produce several types of chemical compounds. These include:

• Iridoid compounds: These are widely produced across the order to deter herbivores.1
• Cardiotonic glycosides: These substances, which have specific toxic effects on the vertebrate heart, are also utilized by some members of the order for defense.12
• Indole alkaloids: Many species in the order produce these nitrogen-containing compounds to discourage consumption.1

These substances serve as chemical defenses, often acting as deterrents that make the plant unpalatable or toxic to potential predators. While these compounds are effective, some specialized herbivores have evolved mechanisms to tolerate or even sequester them for their own protection.132