Rishitin

Ribonuclease, deoxy P1NT576 Ribonuclease P1NT576 Rishitin ... 

Kodama, H., T. Fujimori, and K. Kato. Glucosides of ionone-related compounds in several Nicotiana species. Phytochemistry 1984 23(3) 583-585. Kodama, H., T. Fujimori, and K. Kato. A nor-sesquiterpene glycoside, rishitin-beta-sophoroside, from tobacco. Phytochemistry 1984 23(3) 690-692. 

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

Ishiguri, Y., Tomiyama, A.K., Murai, A., Katsui, N., Masamune, N. Toxicity of rishitin, rishitin-M-1, andrishitin-M-2 to Phytophthora infestans and potato tissue. Ann Phytopathol Soc Japan 1978 44 52-56. 

Lyon, G.D. Evidence that the toxic effect of rishitin may be due to membrane damage. J Exper Bot 1980 31 957-966. 

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

Suleman, P., Tohamy, A.M., Saleh, A. A., Madkour, M.A., Straney, D.C. Variation in sensitivity to tomatine and rishitin among isolates of Fusarium oxysporum f. sp. lycopersici, and strains not pathogenic on tomato. Physiol Mol Plant Pathol 1996 48 131-144. 

Yao M.K. Desilets H., Charles M.T., Boulanger R. Tweddell R.J. Effect of mycorrhization on the accumulation of rishitin and solavetivone in potato plantlets challenged with Rhizoctonia solani. Mycorrhiza 2003 13 333-336. 

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 sesquiterpenoid, rishitinol (306), co-occurring with rishitin (307) in diseased potato tubers, has been identified.Its low-yield synthesis starting from (308) is also reported. 

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. ... 

Thus it has been shown that addition of sodium [ C2]acetate to potato tuber slices, which have been inoculated with Monilinia fructicola or Glomeralla cingulata, provides rishitin (549), lubimin (550), hydroxylubimin (551), 15-dihydrolubimin (552), solavetivone (553), isolubimin (554), 10-epilubimin (555),... 

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... 

Tuber slices (338 kg) (1.5-2,0 mm thickness) of Ri cultivar Rishiri were inoculated with a zoospore suspension (250000-500000 zoospores/ml) of incompatible race of Phytophthora infestans (Mont.) de Bary, race 0 and incubated at 18-20°C for two days. The inoculated slices were stored in an ice-box (-30°C) for a week and then immersed in methanol (250 1) for a week. The supernatant was separated by decantation and the process was repeated twice with methanol (2 x 150 ml). The methanol extracts were combined and concentrated under reduced pressure below 30°C. The concentrate was extracted with chloroform and evaporated to yield oily residue from which a solid material was precipitated on treatment with acetone and was then removed by filtration. The filtrate w as c oncentrated to yield an o ily residue which w as treated with hexane. The hexane solution was concentrated, extracted with ether and washed with aqueous sodium carbonate (10%) and hydrochloric acid (0.1 M) to remove acidic and basic components. The ether extract was washed with water, dried and evaporated. The residue, which contained many c ompounds (by tlc) w as subjected toehromatographic p urification over silicic acid (Mallinckrodt, AR-100) and celite. Benzene ether (1 1 and 1 2) afforded crude rishitin which showed an almost single spot on tic. This was chromatographed over silica gel (Merck). Ether eluted pure rishitin (40) (3.9 g, from 338 Kg tuber slices), m.p. 65-67°C, [ai]-35.1°, max s, 3060,1640 and 890 cm 1 1HNMR 51.12 (3H, d, J=6 Hz), 3.12 (1H, t, J=9Hz),3.55 (lH,br,do,d, J=9and7 Hz), 4.18 (2H, br, s, 2 OH) C,3NMR 148.9 (Cn), 129.0 (C5), 124.9 (C10), 10.9 (C12), 79.2 (C8), 71.5 (C2), 41.6 (C7), 40.4 (C4), 38.3 (C8), 31.1 (C6), 29.7 (C9), 26.5 (C,), 21.0 (C13), 16.4 (Cm).22... 

Rishitin reaches two days after infection a concentration of about 100 g/g fresh weight of tuber tissue. This concentration is enough to delay hyphal growth of P. infestans in resistant tuber tissue. It leads one to think that rishitin may play some role in the defense reaction of potato tubers to infection by pathogen. Owing to growth retardant effect, rishitin may affect the parasite and host plant tissue. Further investigation is required to clarify the role of rishitin in the metabolism of both parasite and host and the host-parasite relationship. 

Masamune and collaborators have accomplished26 a total synthesis or rishitin (40) from a-santonin and this is described in Scheme 4. 

Scheme 4 Compound (45) prepared from a-santonin (41), on reduction afforded alcohol (46), which was converted to derivative (48) by standard organic reaction. Irradiation of (48) in benzene at room temperature followed by reflux in tetrahydrofuran and 2-propanol, produced 15-oxime derivative (49). Its conversion to nitrile (50) was achieved by treatmente with acetic anhydryde in pyridine. Dehydration of (50) followed by decyanation, yielded compound (52). Its acetonide derivative (53), was converted to compound (54), whose convertsion to rishitin (40), was achieved by heating with 0.5% PPA in ethanol...

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. 

It has been already reported in this article that extracts from tubers of potato, variety Rishri, on elution with benzene ether (1 1 and 1 2) afforded crude rishitin. Further elution with benzene ether (3 2) afforded an oil (4.8 g) which was again dissolved in ether. The ether solution was washed with aqueous sodium carbonate (10%), hydrochloric acid (1M) solution and water respectively. The organic extract was dried and evaporated until obtain an oil, which contained two main components as evidenced by TLC. 

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