Isogeraniol (3,7-Dimethyl-3,6-octadien-1-ol): Ein neues Monoterpen bei der Sorte Muscat Roy (Vitis vinifera L.)Der Monoterpengehalt im Most der Neuzüchtung Vitis vinifera L. cv. Muscat Roy und ihrer Elternsorten Muscat Frontignan und Dabuki wurde untersucht. Das Monoterpenprofil von Muscat Roy ist dem von Muscat Frontignan sehr ähnlich. Trotzdem enthält es wesentlich höhere Konzentrationen an Geraniol und α-Terpineol. Im Most von Muscat Roy wurde ein neuer Monoterpenalkohol, 3,7-Dimethyl-3,6-octadien-1-ol (Isogeraniol) identifiziert; im Most der Elternsorten ist jedoch kein Isogeraniol nachweisbar

Bravdo, B. A.

Cohen, S.

Goldman, A.

Ikan, R.

Shoseyov, O.

Siegel, D.

English

JKI Open Journal Systems (Julius Kühn-Institut)

Vitis 29, 159-163 (1990) Department of Horticulture, The Faculty of Agriculture, The Hebrew University of Jerusalem, Israel Iso-geraniol (3,7-dimethyl-3,6-octadien-1-ol): A novel monoterpene in Vitis vinifera L. cv. Muscat Roy by 0. SHOSEYOV1), B. A. BRAVDO, D. SIEGEL, A. GOLDMAN2), s. COHEN and R. IKAN Isogeraniol (3, 7 -Dimethyl-3,6-octadien-1-ol): Ein neues Monoterpen bei der Sorte Muscat Roy (Vitis vinifera L.) Zu s am m e n f a s s u n g : Der Monoterpengehalt im Most der Neuzüchtung Vitis vm1-fera L. cv. Muscat Roy und ihrer Elternsorten Muscat Frontignan und Dabuki wurde untersucht. Das Monoterpenprofil von Muscat Roy ist dem von Muscat Frontignan sehr ähnlich. Trotzdem ent-hält es wesentlich höhere Konzentrationen an Geraniol und a-Terpineol. Im Most von Muscat Roy wurde ein neuer Monoterpenalkohol, 3,7-Dimethyl-3,6-octadien-1-ol (Isogeraniol) identifiziert; im Most der Elternsorten ist jedoch kein Isogeraniol nachweisbar. K e y wo r d s : iso-geraniol, terpene, flavour, constituent, must, new breeding, variety of vine. Introduction The selection of new varieties for better fruit flavor is one of the most difficult goals plant breeders ever aspired to. Since flavor compounds are secondary metabo-lites, their formation depends on many gene products and therefore the 'inheritance of flavor' is not well understood. The role of the monoterpenes in flavor of musts and wines has been reviewed (MARAIS 1983; RAPP et al. 1984; STRAUSS et al. 1986). lt has been established that Muscat varieties contain more monoterpenes, such as linalool (RIBER-EAU-GAYON et al. 1975), as compared to Sauvignon blanc (AuGUSTYN et al. 1982) and Chardonnay (SIMPSON and MILLER 1984). Sauvignon blanc and Chardonnay contain lower concentrations of monoterpenes with different flavor compound profiles. Muscat Roy (Muscat Frontignan x Dabuki) is a new wine grape cultivar developed by Prof. SPIEGEL-ROY (Volcani Institute, Israel). The delicate Muscat flavor and lack of bitterness of its wine (unpublished data) encouraged us to study the monoterpene con-tent of this promising cultivar. We report the identification of iso-geraniol, a new monoterpene alcohol in grapes and the comparison of the monoterpene content between Muscat Roy and its parental cultivars. Materials and methods Monoterpene extraction and identification Grapes of Dabuki, Muscat Frontignan, and Muscat Roy (Vitis vinifera L.) were obtained from the Shfela region of Israel. The grapes were processed immediately after 1) Current address to which all correspondence should be addressed: Department of Horticulture, The Faculty of Agriculture, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel. 2) Deceased 1987. 160 0. SHOSEYOV, B. A. BRAVDO, D. SIEGEL, A. GOLDMAN, s. COHEN and R. IKAN the harvest and 250 ml of musts were extracted by freon 11 according to RAPP et al. (1976). Freon samples were concentrated to 100 µl and injected into either a Finnigen MAT 4600 GC-MS system or to a GC Varian-3700 equipped with 60 m 0.32 mm i.d. Supelcowax-10 column (Supelco). Helium served as carrier gas and GC temperature was programmed as follows: 5 min at 60 °C, then increased to 230 °C at 2 °C/min. Ioni-zation energy was 70 eV. All MS identifications were confirmed by injecting authentic standards. Iso-geraniol {3,7-dimethyl-3,6-octadien-1-ol) preparation Iso-geraniol was prepared according to ARPINO et al. {1977), except sodium dichro-mate was substituted as the oxidizer. 15 ml of 16.8 mM sodium dichromate in sulfuric acid (2.5 g sodium dichromate were dissolved in 1.9 ml concentrated sulfuric acid, then 12.5 ml H20 were added) were added dropwise to 10 ml of 50 mM geraniol in ether in a round bottom flask at a rate of 1 ml/min. The mixture was stirred for 2 hat room tem-perature, at which time the organic phase was separated, washed twice with an equal volume of water, once with 5 % sodium carbonate solution, and again with water. Dehydrated magnesium sulfate was added to the organic phase (to remove water trace) and filtered after 15 min. The ether was removed by vacuum. The oily residue was dis-solved in freon 11 and subsequently injected into GC-MS. Results and discussion In the course of our work we identified a new monoterpene alcohol in the grapes of Muscat Roy. The new monoterpene was identified as 3,7-dimethyl-3,6-octadien-1-ol, which is also known as iso-geraniol. The mass spectrum shown in Fig. 1 as well as the retention time of grape iso-geraniol (Fig. 2) were identical to the data of the synthetic compound. The partial oxidation of geraniol resulted in the formation of citral (gera-nial) as a major product and iso-geraniol as a minor constituent (Fig. 2, peaks no. 1 and 2, respectively), coinciding with the results of ARPINO et al. {1977). The concentration of iso-geraniol in the must was 50 µg/l (Table). Iso-geraniol was previously identified in the flowers of the small evergreen tree Zinchoge (Daphne odora THUNB.) by WATANABE et al. {1982) and in the essential oil of Petitgrain Eureka lemon fruit by BAALIOUAMER et al. {1985). Since no sensing threshold value for iso-geraniol is available, its effect on the flavor of Muscat Roy remains in question. However, the fact that no one has ever reported its presence in grapes led us to examine the monoterpene content of the pa-rental cultivars of Muscat Roy (Muscat Frontignan and Dabuki). Both cultivars are Vitis vinifera L., the latter cultivar is a local white table grape. The table summarizes the GC-MS must data of the three cultivars. As expected, Muscat Frontignan contains more monoterpenes, such as linalool and citronellol, compared with Dabuki (a non-muscat cultivar). Muscat Roy shows a profile similar to Muscat Frontignan regarding most monoterpenes, thus explaining itS Muscat flavor. However, iso-geraniol was found only in Muscat Roy. lt seems odd to find in a cultivar a compound that is unde-tectable in its parental cultivars. The relatively high concentration of a-terpineol in Dabuki and Muscat Roy has very little contribution to the flavor due to its high sensing threshold (MARAIS 1983), but is indicative of higher oxidative conditions in both culti-vars. One may speculate that Dabuki inherited oxygenase and isomerase genes result-ing in monoterpenes of a high oxidative state. In such biochemical conditions when monoterpenes are present in high concentrations (inherited by Muscat Frontignan), a new monoterpene, such as iso-geraniol, could be formed. Iso-geraniol in cv. Muscat Roy 41 108.11 79 „ 121 39 107 "" 77 .. •• „ •• .. „ „ 154 „ 1 l 1 ~ r 'L 139 1 IVZ „ „ .„ .„ .„ Fig. 1: Mass spectrum of iso-geraniol (3,7-dimethyl-3,6-octadien-1-ol). Massenspektrum von Isogeraniol (3,7-Dimethyl-3,6-octadien-1-ol). The monoterpene content of Muscat Frontignan, Dabuki and their progeny Muscat Roy Monoterpengehalt von Muscat Frontignan, Dabuki und ihrem Abkömmling Muscat Roy Monoterpene Muscat Dabuki Muscat (µg/l) Frontignan Roy cis-furan-linalooloxide 20 20 30 trans-furan-linalooloxide 30 15 15 linalool 210 20 350 a-terpineol 20 200 180 cis-pyran-linalooloxide 190 50 230 trans-pyran-linalooloxide 5 5 5 citronellol 120 30 110 nerol 40 5 60 iso-geraniol 50 geraniol 50 20 150 161 230. In conclusion, prediction of the flavor of a given cultivar by evaluating its parental cultivars is presently unreliable. The mechanism by which various monoterpenes are inherited is not fully understood and when breeding for flavor compounds a high rate of diversity is to be expected. 162 0. SHOSEYOV, B. A. BRAVDO, D. SIEGEL, A. GOLDMAN, s. COHEN and R. IKAN 0 1 i 1 "! 1 ·.1 ' 1 1 • 1' ISOGERANIOL · 3,7,-Dimethyl-3,6-octadien-1-ol · 1 1----· L ... ! . „6. ·5 •• -- :- -- ··1-·-. 4.i !: j •• l „; ; ···--·-··---·· ·- ! ! .. ~--.-.-~~---3„ 1 ' I· T !: ·i·-. ·-t i" ' [~- . 2 ~ „. : -- t . -~-· _) ___ . t · i ~ i · ! ck \:-, Jt :: ·:LJ_~1k+,:. 15 i- ! 1 : . 1 __ !. 1 -1 :I . !" ·-i:' .............. t-'1 ... 1 ..... • ~·1~:··1_J;, ___ i:_ 1 1 i . ~~ . . ! 30 R.t. min 45 Fig. 2: GC analysis of geraniol that was partially oxidized with sodium dichromate. 1 = geranial (citral), 2 = iso-geraniol (3,7-dimethyl-3,6-octadien-l-ol), 3 = geraniol. GC-Analyse von mit Natriumdichromat partiell oxidiertem Geraniol. 1 = Geranial (Citral), 2 = Iso-geraniol (3,7-Dimethyl-3,6-octadien-l-ol), 3 = Geraniol. Summary The must monoterpene content of the new Vitis vinifera L. cultivar Muscat Roy and its parental cultivars, Muscat Frontignan and Dabuki, was studied. The monoter-pene profile of cv. Muscat Roy is very similar to that of Muscat Frontignan. However, it contains significantly higher concentrations of geraniol .and a-terpineol. A new mono-terpene alcohol, 3,7-dimethyl-3,6-octadien-1-ol (iso-geraniol), was identified in the must of Muscat Roy, but not in the musts of its parental cultivars. lso-geraniol in cv. Muscat Roy 163 Acknowledgements We thank Prof. Dr. A. RAPP for providing us with the mass spectrum data of grape monoter-penes and his valuable contribution in setting the monoterpenes analysis system. We also thank Mrs. NEHAMA BAR, Mrs. LISA SHOSEYOV and Mrs. MARINA CHARNIAK for their skillful technical assist-ance. This study was partially supported by BARD US-1018-85. Literature ARPINO, P.; VIDAL-MADJAR, C.; GUROCHON, G.; 1977: Production of citral from geraniol. II. Capi!lary gas chromatographic-mass spectrometric investigation of two different oxidation reactions using a graphite porous-layer open tubular column with !arge coating ratio of polar liquid phase. J. Chromatogr.138, 173-182. Aum.:STIN, 0. P. H.; RAPP, A.; VA<'I WYK, C.J.; 1982: Some volatile aroma components of Vitis vini-fera L. cv. Sauvignon blanc. S. Afr. J. Enol. Viticult. 3, 53-60. BAALIOUAMER, A.; MEKLATI, B. Y.; FRAISSE, D.; ScHARFF, C.; 1985: Qualitative and quantitative analysis of Petitgrain Eureka lemon essential oil by fused silica capillary column gas chromatography mass spectrometry. J. Sei. Food Agricult. 36, 1145--1154. MARAJS, J.; 1983: Terpenes in the aroma of grapes and wines: A review. S. Afr. J. Enol. Viticult. 4, 49-60. RAPP, A.; HASTRICH, H.; ENGEL, L.; 1976: Gaschromatographische Untersuchungen über die Aroma-stoffe von Weinbeeren. 1. Anreicherung und kapillarchromatographische Auftrennung. Vitis 15,29-36. - - ; MANDERY, H.; GüNTER, M.; 1984: Terpene compounds in wine. In: NYKANEN, L.; LEHTONEN, P. (Eds.): Proceedings of the Alko Symposium on Flavour Research of Alcoholic Beverages. Hel-sinki, FBIFR 3, 255--274. R.!BEREAU-GAYON, P.; BOIDRON, J. N.; TERRIER, A.; 1975: Aroma of Muscat grape varieties. J. Agricult. Food Chem. 23, 1042-1047. SIMPSON, R. F.; MILLER, G. C.; 1984: Aroma composition of Chardonnay wine. Vitis 23, 143-158. STRAUSS, c. R.; WILSON, B.; GooLEY, P. R.; WILLIAMS, R.J.; 1986: Role of monoterpenes in grape and wine flavor. In: PARLIMENT„T. H.; CROTEAU, R. (Eds.): Biogeneration of Aromas, 222-242, ACS, Washington. WATANABE, I.; YANAI, T.; AwANO, K.; KOGAM!, K.; liAYASHI, K.; 1982: Volatile components of Zinchoge flower (Daphne odora THUNB.). Agricult. Bio!. Chem. 47, 483-490. Eingegangen am 16. 10. 1989 Dr. 0. SHOSEYOV Department of Biochemistry and Biophysics Briggs Hall UCDavis Davis, California 95616 USA 

Iso-geraniol (3,7-dimethyl-3,6-octadien-1-ol): A novel monoterpene in Vitis vinifera L. cv. Muscat Roy

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Iso-geraniol (3,7-dimethyl-3,6-octadien-1-ol): A novel monoterpene in Vitis vinifera L. cv. Muscat Roy

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