Phytoalexin rishitin

Hodgkin, T., Lyon, G.D. Inhibition of Solanum pollen germination in vitro by the phytoalexin rishitin. Ann Bot 1979 44 253-255. 

Lyon, GD., Mayo, M.A. The phytoalexin rishitin affects the viability of isolated plant protoplasts. Phytopathol Z 1978 92 294-304. 

The latter are formed as stress metabolites after infection by fungi or bacteria such as Erwinia carotovora and Phytophthora infestans together with other compounds such as phytuberin. Compounds (3), (4), (5), and (6) in the given order are precursors in the biosynthesis of the phytoalexin rishitin. The V. are formed biosynthetically from eudesmane type sesquiterpenes. Lit. J. Am. Chem. Soc. 120, 1747 (1998) (synthesis) Tetrahedron Lett. 37, 8703 (1996). 

Murai A, Sato S, Osada A, Katsui N, Masamune T (1982a) Biosynthesis from solavetivone of the phytoalexin rishitin in potato. Implicit role of solavetivone as an activator. J Chem Soc, Chem Commun 32-33... 

Bicyclic sesquiterpenes include a variety of bioactive compounds including the Solanaceae phytoalexins capsidiol (G61G6) from Capsicum frutescms (pepper) and the Solanum tuberosum (potato) antifungals rishitin (G61C6) and solavetivone (G6-G5) the Ipomoea batatus... 

A new HPLC technique has been developed for the rapid analysis of sesquiterpene phytoalexins such as capsidiol, rishitin, luminin, and phytuberol. This method employs a cyanopropyl-bonded phase column with an isocratic mixture of hexane and isopropanol. Flame ionization and UV detection were used for the analysis of capsidiol, rishitin, lubimin, phytuberol, and debneyol. Although both detectors proved to be useful, the signal response with the flame ionization detector was proportional to the mass of each of the phytoalexins, while the signal with the UV detector was proportional to the number of carbon—carbon bonds in each of the compounds. 

Murai, A., Abiko, A., Ono, M., Masamune, T., Studies on the Phytoalexins. 31. Synthetic Studies of Rishitin and Related Compounds. 11. Synthesis of Aubergenone, a Sesquiterpenoid Phytoalexin from Diseased Eggplants, Bull. Chem. Soc. Jpn. 1982, 55, 1191 1194. 

Remote functionalization of the angular methyl group in santonin derivatives has also been accomplished using the Barton reaction. For example a key step in the previously reported synthesis of the norsesquiterpenoid rishitin (450) from tetrahydro-a-santonin (443) involves photochemical transformation of the nitrite ester (447) to the oxime (448) (c/. Scheme 46). Rishitin (450) is a well known antifungal phytoalexin produced by diseased potato tubers and recent studies... 

An investigation of the metabolism of sesquiterpenoid phytoalexins has shown that pepper or potato cell cultures can convert capsidiol (485) and rishitin (450) into their 13-hydroxy-derivatives cf. p. 136). Solavetivane derivatives of this type have previously been isolated from flue-cured tobacco (Vol. 8, p. 107). New chemical and spectroscopic evidence has led to a revised configuration for the 3-hydroxy- or 3-acyloxy-substituent in furanofukinol (486) (Petasites japonica Maxim.) and the related esters (487) and (488), previously isolated from Farfugium hiberniflorum Kitam. ... 

Rishitin (40) is an antifiigal norsesquiterpene, qualified as phytoalexin and this was isolated from tuber tissues of white potatoes infected by an incompatible race of Phytophthora infestans. It was isolated21 by... 

Katsui et al.,76 isolated two phytoalexins sesquiterpenes lubimin (144) and oxylubimin (145) from white potato tubers (Rishri) infected by an incompatible race of Phytophthora infestans. It has already been mentioned that from white potato tubers also have been isolated sesquiterpene rishitin (40). In the year 1971 Metliskii and coworkers77 isolated lubimin (144) along with rishitin (40) from white potato tubers (S.tuberlosum Lubimets ) stressed with various pathogens. 

A number of sesquiterpene phytoalexins accumulate in potato (Solanum tuberosum) in response to attack by Monol-inia fruticola, Phytophthora infestans, mdAlternaria solani. Among these are rishitin (32), lubimin (33), phytotuberin (34), and several other sesquiterpenes (Brooks and Watson, 1985 Kuc, 1992). Cell walls of P. infestans contain an elici-tor of ph) oalexin accumulation in potato (Kuc, 1982). Similar phytoalexins are synthesized by a number of other solana-... 

Fig. 2. Biosynthesis of some sesquiterpene phytoalexins. Phytub rin, solavetivone, lubimin, hydroxylu-bimin and rishitin are produced by Phytophthora-iniected potatoes (Soianum tuberosum) and by potato tuber disks treated with Elicitor (see). Capsidiol is a phytoalexin from Capsicum, [P.A.Brindle D.R.Threlfall Biochem. Society Transactions ft (1983) 516-522]...

Fig. 7.5 Solanaceous sesquiterpenoidal/worsesquiterpenoidal phytoalexins and their biogenetic relations. Formation of rishitin (Cj ) by elimination of the exocycUc C-15 (highlighted in grey) presumably via oxidation of CHO to COOH followed by decarboxylation (the corresponding lubiminoic acid was identified as a constituent of Solanum aethiopicum)...

Further Species. Interestingly, tropane alkaloid accumulating species like Datura stramonium L. or Hyoscyamus albus L. were also found to accumulate major solanaceous phytoalexins such as solavetivone, lubimin, and rishitin as a consequence of an inoculation with fungi (Stoessl et al. 1976 Miguel and Barroso 1994). Eurthermore, 2a,3P-dihydroxygermacrene A (Eig. 7.5) was identified as another stress metabolite in the former species. 

A common response of plants, often associated with disease resistance, is the localized and rapid death of plant cells at the infection site. This reaction, referred to as a hypersensitive response (HR), Includes the accumulation of phytoalexins (low molecular weight compounds which Inhibit microbial development). In some plant-parasite interactions, different races of a pathogen can be distinguished by the type of response they elicit in different cultivars. Incompatible races of Phytophthora infestans elicit the accumulation of sesquiterpenoid phytoalexins, principally rishitin and lubimin, in tubers of resistant (R-gene) cultivars faster to higher levels following infection than do... 

In light of the role of Ca in transduction of external stimulus to cellular response in a wide variety of animal and plant cells, >23 it was reasonable to investigate whether Ca is involved in the elicitation of phytoalexin accumulation. The stimulatory effects of Ca2+ and the inhibitory effects of Ca antagonists on rishitin and lubimin accumulation suggest that Ca mobilization is an essential part of the elicitation of phytoalexin accumulation in potato tuber tissue. 

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