Phytoalexins: plants stress-inducible metabolites

Phytoalexins: plants stress-inducible metabolites The plant stress-inducible metabolites are mainly indued by plants in order to face pathogen attacks as a part of a number of defense mechanise (lytic and oxidative enzymes, cell wall lignifications, etc) conceived to overcome unfavourable conditions. 

Exposure to cold, ultraviolet light, physical damage, and certain chemical compounds such as metal salts, polyamines, and certain pesticides can elicit the production of phytoalexins. This hypersensitive response may all be triggered by a rye of abiotic inducers or by carbohydrate glucan elicitors derived from the cell walls of yeasts or fungi.

The French botanist Noel Bernard in 19911 observed orchid tubers and defined phytoalexins as ‘chemical compounds produced as a result of invasion of living cells by a parasite'. Phytoalexins are usually elicited locally at the site of attack. Some evidence exists for accumulation of phytoalexins in edible tissue, particularly in potatoes and sweet potatoes.

The classic example of phytoalexin production occurs in potatoes inoculated with the blight fungus, Phytophthora infestans. When inoculated onto the potato, certain strains of this fungus will initially grow rapidly, followed by gradual slowing of growth.

Isoflavonoids phytoalexins are also known as normal products in other plant species. It this follows that screening of leguminous plants for antimicrobial activity will inevitably lead to the isolation of active isoflavonoids, and will probably yields other stress not represented in the phytoalexins. Some phytoalexins have been demonstrated to be toxic to humans.

Generally stress metabolises possess some degree of toxicity to living matter and given that this toxicity can be extended t humans, one must consider there importance in the context of human and livestock safety.

Phytoalexins are often detected initially by their antifungal activity. The most widely technique is the thin layer chromatography bioassay.
Phytoalexins: plants stress-inducible metabolites