Phytoalexins are antibiotics produced by plants that are under attack. 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. Resveratrol is also one of 300 identified Salvestrols. Salvestrols are invited into each cell of body. Abnormal cells, including malignant cells contain an enzyme system called CYP1B1. When this enzyme combines with a salvestrol a toxin is produced. This toxin kills the abnormal or malignant cell.
Phytoalexins produced in plants act as toxins to the attacking organism. They may puncture the cell wall, delay maturation, disrupt metabolism or prevent reproduction of the pathogen in question. However, phytoalexins are often targeted to specific predators; a plant that has anti-insect phytoalexins may not have the ability to repel a fungal attack.
When a plant cell recognizes particles from damaged cells or particles from the pathogen, the plant launches a two-pronged resistance: a general short-term response and a delayed long-term specific response.
As part of the induced resistance, the short-term response, the plant deploys free radicals such as superoxide and hydrogen peroxide to kill invading cells. In pathogen interactions, the common short-term response is the hypersensitive response, wherein apoptosis-compromised cells commit suicide in order to create a physical barrier for the invader.
Long-term resistance, or systemic acquired resistance (SAR), involves communication of the damaged tissue with the rest of the plant using plant hormones such as jasmonic acid, ethylene, abscisic acid or salicylic acid. The reception of the signal leads to global changes within the plant, which induce genes that protect from further pathogen intrusion, including enzymes involved in the production of phytoalexins. Often, if jasmonates or ethylene (both gaseous hormones) is released from the wounded tissue, neighboring plants also manufacture phytoalexins in response. For herbivores, common vectors for disease, these and other wound response aromatics seem to act as a warning that the plant is no longer edible. Also, in accordance with the old adage, “an enemy of my enemy is my friend,” the aromatics may alert natural enemies of the plant invaders to the presence thereof.
Phytoalexin in Recent Research
Allixin (3-hydroxy-5-methoxy-6-methyl-2-penthyl-4H-pyran-4-one), a non-sulfur containing compound having a g-pyrone skeleton structure, was the first compound isolated from garlic as a phytoalexin, a product induced in plants by continuous stress. This compound has been shown to have unique biological properties, such as anti-oxidative effects, anti-microbial effects, anti-tumor promoting effects, inhibition of aflatoxin B2 DNA binding, and neurotrophic effects. Allixin showed an anti-tumor promoting effect in vivo, inhibiting skin tumor formation by TPA in DMBA initiated mice. Analogs of this compound have exhibited anti tumor promoting effects in in vitro experimental conditions. Herein, allixin and/or its analogs may be expected useful compounds for cancer prevention or chemotherapy agents for other diseases.