Phytoalexins are
antimicrobial and often
antioxidative substances synthesized
de novo by
plants that accumulate rapidly at areas of pathogen infection. They are broad spectrum inhibitors and are chemically diverse with different types characteristic of particular plant species. Phytoalexins tend to fall into several classes including
terpenoids,
glycosteroids and
alkaloids; however, researchers often find it convenient to extend the definition to include all
phytochemicals that are part of the plant's defensive arsenal.