Capsidiol is a phytoalexin produced by certain plants in response to pathogenic attack.
Phytoalexins areantimicrobial substances, some of which areantioxidative as well. They are defined not by their having any particular chemical structure or character, but by the fact that they are defensively synthesizedde novo byplants that produce the compounds rapidly at sites of pathogen infection. In general phytoalexins are broad spectrum inhibitors; they are chemically diverse, and different chemical classes of compounds are characteristic of particular planttaxa. Phytoalexins tend to fall into several chemical classes, includingterpenoids,glycosteroids, andalkaloids; however, the term applies to anyphytochemicals that are induced by microbial infection.
Phytoalexins are produced in plants to act as toxins to the attacking organism. They may puncture thecell wall, delay maturation, disrupt metabolism or prevent reproduction of the pathogen in question. Their importance in plant defense is indicated by an increase in susceptibility of plant tissue to infection when phytoalexin biosynthesis is inhibited. Mutants incapable of phytoalexin production exhibit more extensive pathogen colonization as compared to wild types. As such, host-specific pathogens capable of degrading phytoalexins are more virulent than those unable to do so.[1]
When a plant cell recognizes particles from damagedcells or particles from the pathogen, the plant launches a two-pronged resistance: a general short-term response and a delayed long-term specific response.[citation needed]
As part of the induced resistance, the short-term response, the plant deploysreactive oxygen species such assuperoxide andhydrogen peroxide to kill invading cells. In pathogen interactions, the common short-term response is thehypersensitive response, in which cells surrounding the site of infection are signaled to undergoapoptosis, or programmed cell death, in order to prevent the spread of the pathogen to the rest of the plant.[citation needed]
Long-term resistance, orsystemic acquired resistance (SAR), involves communication of the damaged tissue with the rest of the plant usingplant hormones such asjasmonic acid,ethylene,abscisic acid, orsalicylic acid. The reception of the signal leads to global changes within the plant, which induce expression of genes that protect from further pathogen intrusion, including enzymes involved in the production of phytoalexins. Often, if jasmonates or ethylene (both gaseous hormones) are released from the wounded tissue, neighboring plants also manufacture phytoalexins in response. For herbivores, commonvectors forplant diseases, these and other wound response aromatics seem to act as a warning that the plant is no longer edible.[citation needed] 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.
Allixin (3-hydroxy-5-methoxy-6-methyl-2-pentyl-4H-pyran-4-one), a non-sulfur-containing compound having aγ-pyrone skeletal structure, was the first compound isolated fromgarlic as a phytoalexin, a product induced in plants by continuousstress.[2] This compound has been shown to have unique biological properties, such as anti-oxidative effects,[2] anti-microbial effects,[2] anti-tumor promoting effects,[3] inhibition ofaflatoxin B2DNA binding,[4] and neurotrophic effects.[4] Allixin showed an anti-tumor promoting effect in vivo, inhibiting skintumor formation byTPA inDMBA initiated mice.[3] Herein, allixin and/or its analogs may be expected to be useful compounds for cancer prevention or chemotherapy agents for other diseases.[citation needed]
Role of natural phenols in the plant defense against fungal pathogens
^abNishino H, Nishino A, Takayama J, Iwashima A, Itakura Y, Kodera Y, Matsuura H, Fuwa T (1990). "Antitumor promoting activity of allixin, a stress compound produced by garlic".Cancer J.3:20–21.
^abYamasaki T.; Teel R. W.; Lau B. H. S. (1991). "Effect of allixin, a phytoalexin produced by garlic, on mutagenesis, DNA-binding and metabolism of aflatoxin B1".Cancer Lett.59 (2):89–94.doi:10.1016/0304-3835(91)90171-D.PMID1909211.
^Timperio, Anna Maria; d’Alessandro, Angelo; Fagioni, Marco; Magro, Paolo; Zolla, Lello (2012). "Production of the phytoalexins trans-resveratrol and delta-viniferin in two economy-relevant grape cultivars upon infection withBotrytis cinerea in field conditions".Plant Physiology and Biochemistry.50 (1):65–71.doi:10.1016/j.plaphy.2011.07.008.PMID21821423.
^Mercier, J.; Arul, J.; Ponnampalam, R.; Boulet, M. (1993). "Induction of 6-Methoxymellein and Resistance to Storage Pathogens in Carrot Slices by UV-C".Journal of Phytopathology.137:44–54.doi:10.1111/j.1439-0434.1993.tb01324.x.
^Hoffman, R.; Heale, J.B. (1987). "Cell death, 6-methoxymellein accumulation, and induced resistance toBotrytis cinerea in carrot root slices".Physiological and Molecular Plant Pathology.30:67–75.doi:10.1016/0885-5765(87)90083-X.
^Echeverri, Fernando; Torres, Fernando; Quiñones, Winston; Cardona, Gloria; Archbold, Rosendo; Roldan, Javier; Brito, Ivan; Luis, Javier G.; Lahlou, El-Hassane (1997). "Danielone, a phytoalexin from papaya fruit".Phytochemistry.44 (2):255–256.Bibcode:1997PChem..44..255E.doi:10.1016/S0031-9422(96)00418-9.PMID9004541.
^Hart, John H.; Hillis, W. E. (1974). "Inhibition of wood-rotting fungi by stilbenes and other polyphenols inEucalyptus sideroxylon".Phytopathology.64 (7):939–48.doi:10.1094/Phyto-64-939.
Moriguchi, Toru; Matsuura, Hiromichi; Itakura, Yoichi; Katsuki, Hiroshi; Saito, Hiroshi; Nishiyama, Nobuyoshi (1997). "Allixin, a phytoalexin produced by garlic, and its analogues as novel exogenous substances with neurotrophic activity".Life Sciences.61 (14):1413–1420.doi:10.1016/S0024-3205(97)00687-5.PMID9335231.
