glucotropaeolin

The compound was first reported in 1899, after its isolation from Tropaeolum majus, a nasturtium species.{{cite journal |doi=10.1016/j.phytochem.2019.112100 |doi-access=free |title=Glucosinolate structural diversity, identification, chemical synthesis and metabolism in plants |year=2020 |last1=Blažević |first1=Ivica |last2=Montaut |first2=Sabine |last3=Burčul |first3=Franko |last4=Olsen |first4=Carl Erik |last5=Burow |first5=Meike |last6=Rollin |first6=Patrick |last7=Agerbirk |first7=Niels |journal=Phytochemistry |volume=169 |page=112100 |pmid=31771793 |s2cid=208318505 }}{{rp|Section 2}} Glucotropaeolin is now known to occur widely in other brassica families including Caricaceae, Phytolaccaceae, Resedaceae, Salvadoraceae and Tovariaceae.{{cite journal |doi=10.1016/S0031-9422(00)00316-2 |title=The chemical diversity and distribution of glucosinolates and isothiocyanates among plants |year=2001 |last1=Fahey |first1=Jed W. |last2=Zalcmann |first2=Amy T. |last3=Talalay |first3=Paul |journal=Phytochemistry |volume=56 |issue=1 |pages=5–51 |pmid=11198818 }}

File:Glucotropaeolin unnatural E isomer.svg

The chemical structure of glucotropaeolin was confirmed by total synthesis in 1957. This showed that it is a glucose derivative with β-D-glucopyranose configuration. At that time it was unclear whether the C=N bond was in the Z form, with sulfur and oxygen substituents on the same side of the double bond, or the alternative E form in which they are on opposite sides. The suggestion was made that the Z form was more likely, based on the known decomposition to benzyl isothiocyanate by a mechanism analogous to the Lossen rearrangement.{{cite journal |doi=10.1021/ja01564a066 |title=First Synthesis of a Mustard Oil Glucoside; the Enzymatic Lossen Rearrangement |year=1957 |last1=Ettlinger |first1=Martin G. |last2=Lundeen |first2=Allan J. |journal=Journal of the American Chemical Society |volume=79 |issue=7 |pages=1764–1765 }} However, when an identical product was obtained by an alternative route in 1963, it was pointed out that the E form would be expected to rearrange in a similar way.{{cite journal |doi=10.1139/v63-415 |title=A New Mustard Oil Glucoside Synthesis: The Synthesis of Glucotropaeolin |year=1963 |last1=Benn |first1=M. H. |journal=Canadian Journal of Chemistry |volume=41 |issue=11 |pages=2836–2838 |doi-access=free }} The matter was settled by X-ray crystallography and other spectroscopic studies and it is now known that all natural glucosinolates are of Z form.

Glucotropaeolin is biosynthesised from the amino acid phenylalanine in a multi-step pathway.

The first laboratory syntheses served to confirm the compound's structure. Later work allowed many glucosinolates including this benzyl derivative to be made. These processes are more efficient than isolating pure materials from the plants in which they are naturally found.{{rp|Section 3}}

{{Main|Glucosinolate}}

The natural role of glucosinolates are as plant defense compounds. The enzyme myrosinase removes the glucose group in glucotropaeolin to give an intermediate which spontaneously rearranges to benzyl isothiocyanate. This is a reactive material which is toxic to many insect predators and its production is triggered when the plant is damaged.{{cite journal |doi=10.1016/j.phytochem.2008.03.006 |title=β-Glucosidases as detonators of plant chemical defense |year=2008 |last1=Morant |first1=Anne Vinther |last2=Jørgensen |first2=Kirsten |last3=Jørgensen |first3=Charlotte |last4=Paquette |first4=Suzanne Michelle |last5=Sánchez-Pérez |first5=Raquel |last6=Møller |first6=Birger Lindberg |last7=Bak |first7=Søren |journal=Phytochemistry |volume=69 |issue=9 |pages=1795–1813 |pmid=18472115 }} This effect has been called the mustard oil bomb.{{cite journal |doi=10.1016/S0015-3796(80)80059-X |title="Die Senfolbombe": Zur Kompartimentierung des Myrosinasesystems |year=1980 |last1=Matile |first1=Ph. |journal=Biochemie und Physiologie der Pflanzen |volume=175 |issue=8–9 |pages=722–731 }} At concentrations typically found in foods, the glucosinolates are not toxic to humans and can be useful flavor components.{{cite journal |doi=10.1080/10408398209527361 |title=Glucosinolates and their breakdown products in food and food plants |year=1983 |last1=Fenwick |first1=G. Roger |last2=Heaney |first2=Robert K. |last3=Mullin |first3=W. John |last4=Vanetten |first4=Cecil H. |journal=C R C Critical Reviews in Food Science and Nutrition |volume=18 |issue=2 |pages=123–201 |pmid=6337782 }}

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{{Cruciferous Biochemistry}}

Category:Glucosinolates

Category:Benzyl compounds