Prunasin

Last updated
Prunasin
Prunasin.svg
Names
IUPAC name
(R)-(β-D-Glucopyranosyloxy)(phenyl)acetonitrile
Systematic IUPAC name
(R)-Phenyl{[(2R,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}acetonitrile
Other names
(R)-Prunasin
D-Prunasin
D-Mandelonitrile-β-D-glucoside
Prulaurasin Laurocerasin
Sambunigrin
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.002.489 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 202-738-0
KEGG
PubChem CID
UNII
  • InChI=1S/C14H17NO6/c15-6-9(8-4-2-1-3-5-8)20-14-13(19)12(18)11(17)10(7-16)21-14/h1-5,9-14,16-19H,7H2/t9-,10+,11+,12-,13+,14+/m0/s1
    Key: ZKSZEJFBGODIJW-GMDXDWKASA-N
  • InChI=1/C14H17NO6/c15-6-9(8-4-2-1-3-5-8)20-14-13(19)12(18)11(17)10(7-16)21-14/h1-5,9-14,16-19H,7H2/t9-,10+,11+,12-,13+,14+/m0/s1
    Key: ZKSZEJFBGODIJW-GMDXDWKABY
  • C1=CC=C(C=C1)[C@H](C#N)O[C@H]2[C@@H]([C@H]([C@@H]([C@H](O2)CO)O)O)O
Properties
C14H17NO6
Molar mass 295.291 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

(R)-prunasin is a cyanogenic glycoside related to amygdalin. Chemically, it is the glucoside of (R)-mandelonitrile.

Contents

Natural occurrences

Prunasin is found in species in the genus Prunus such as Prunus japonica or P. maximowiczii and in bitter almonds. [1] It is also found in leaves and stems of Olinia ventosa , O. radiata , O. emarginata and O. rochetiana [2] and in Acacia greggii . It is a biosynthetic precursor of and intermediate in the biosynthesis of amygdalin, the chemical compound responsible for the taste of bitter almond.[ citation needed ]

It is also found in dandelion coffee, a coffee substitute.[ citation needed ]

Sambunigrin

Sambunigrin, a diastereomer of prunasin derived from (S)-mandelonitrile instead of it the (R)-isomer, has been isolated from leaves of the elder tree ( Sambucus nigra ). [3] Sambunigrin is present in the leaves and stems of elder at a 1:3 ratio of sambunigrin to prunasin, and 2:5 in the immature seed. [4] It is not found in the root. [4]

Biosynthesis

Overview

(R)-prunasin begins with the common amino acid phenylalanine, which in plants is produced via the Shikimate pathway in primary metabolism. The pathway is catalyzed mainly by two cytochrome P450 (CYP) enzymes and a UDP-glucosyltransferase (UGT). After (R)-prunasin is formed, it is either converted into amygdalin by an additional UDP-glucosyltransferase or degraded into benzaldehyde and hydrogen cyanide.

Researchers have shown that the accumulation (or lack of) of prunasin and amygdalin in the almond kernel is responsible for sweet and bitter genotypes. [1] Because amygdalin is responsible for the bitter almond taste, almond growers have selected genotypes which minimize the biosynthesis of amygdalin. The CYP enzymes responsible for generation of prunasin are conserved across Prunus species. [5] There is a correlation between high concentration of prunasin in the vegetative regions of the plant and the sweetness of the almond, which is relevant to the almond agricultural industry. In almonds, the amygdalin biosynthetic genes are expressed at different levels in the tegument (mother tissue, or outer section) and cotyledon (kernel, or father tissue), and vary significantly during almond ontogeny. [1] [6] [7] The biosynthesis of prunasin occurs in the tegument, then transported to other tissues for conversion to amygdalin or degraded. [1] [5]

Biosynthesis of (R)-prunasin

Biosynthetic pathway for the production of (R)-prunasin in Prunus species (top) and Eucalyptus cladocalyx (bottom) Prunasin biosynthetic mechanism.gif
Biosynthetic pathway for the production of (R)-prunasin in Prunus species (top) and Eucalyptus cladocalyx (bottom)

Biosynthesis of (R)-prunasin in Prunus dulcis

L-phenylalanine is first hydroxylated by CYP79D16, followed by a decarboxylation and dehydration, forming the E-oxime phenylacetaldoxime. [8] Next, CYP71AN24 catalyzes the rearrangement of the E-oxime to the Z-oxime followed by a dehydration and a hydroxylation to form mandelonitrile. [8] Finally, UGT85A19 or UGT94AF3 utilize UDP-glucose to glycosylate mandelonitrile, forming (R)-prunasin. [1]

After generating (R)-prunasin, the product is further glycosylated into amygdalin by either isoform UGT94AF1 or UGT94AF2. [1] Expression of UGTAF1/2 and prunasin hydrolases results in a low overall concentration of (R)-prunasin in almond tissues. It is important to note that an alpha-glucosidase or prunasin hydrolase can convert (R)-prunasin to mandelonitrile, its precursor, which can then be spontaneously or enzymatically hydrolyzed to benzaldehyde and hydrogen cyanide. [9]

Biosynthesis of (R)-prunasin in Eucalyptus cladocalyx

The biosynthesis of (R)-prunasin in E. cladocalyx, the sugar gum tree, has been shown to synthesize (R)-prunasin using an additional intermediate, phenylacetonitrile, using CYP706C55. [10] The pathway proceeds similarly to the pathway in Prunus species, where the multifunctional CYP79A125 catalyzes the conversion of L-phenylalanine to phenylacetaldoxime. Then, CYP706C55 catalyzes the dehydration of phenylacetaldoxime to phenylacetonitrile. Phenylacetonitrile is then hydroxylated by CYP71B103 to mandelonitrile. After generating mandelonitrile, UGT85A59 transfers glucose to yield (R)-prunasin. [10]

Metabolic Pathway Interactions

As (R)-prunasin is a product of secondary metabolism, its generation and degradation affect multiple metabolic pathways by consuming L-phenylalanine or increasing quantities of benzaldehyde and toxic hydrogen cyanide through prunasin degradation.

Metabolic profiling in almond, cassava, and sorghum identified a potential recycling mechanism where (R)-prunasin and other cyanogen glycosides may be utilized for nitrogen storage and nitrogen recycling without generating HCN. [11] In 2017, researchers used stable isotope labeling to demonstrate that 13C-labeled L-phenylalanine incorporated in (R)-prunasin could be converted to benzaldehyde and to salicylic acid using mandelonitrile as an intermediate. [12]

Toxicity

The toxicity of prunasin is based in its degradation products: (R)-prunasin is hydrolyzed to form benzaldehyde and hydrogen cyanide, which causes toxicity. Plants containing prunasin may therefore be toxic to animals, particularly ruminants. [13]

To degrade amygdalin to prunasin, amygdalin beta-glucosidase hydrolyzes the disaccharide to produce (R)-prunasin and D-glucose. Then, prunasin beta-glucosidase uses (R)-prunasin and water to produce D-glucose and mandelonitrile. After generating the aglycone mandelonitrile, then a mandelonitrile lyase can degrade the compound into benzaldehyde and hydrogen cyanide.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Almond</span> Species of nut

The almond is a species of small tree from the genus Prunus, cultivated worldwide for its seed, a culinary nut. Along with the peach, it is classified in the subgenus Amygdalus, distinguished from the other subgenera by corrugations on the shell (endocarp) surrounding the seed.

<span class="mw-page-title-main">Amygdalin</span> Cyanogenic glycoside present in kernels of fruit

Amygdalin is a naturally occurring chemical compound found in many plants, most notably in the seeds (kernels) of apricots, bitter almonds, apples, peaches, cherries and plums, and in the roots of manioc.

A glucoside is a glycoside that is chemically derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes.

<i>Prunus laurocerasus</i> Species of plant

Prunus laurocerasus, also known as cherry laurel, common laurel and sometimes English laurel in North America, is an evergreen species of cherry (Prunus), native to regions bordering the Black Sea in southwestern Asia and southeastern Europe, from Albania and Bulgaria east through Turkey to the Caucasus Mountains and northern Iran.

<span class="mw-page-title-main">Glycoside</span> Molecule in which a sugar is bound to another functional group

In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. Many such plant glycosides are used as medications. Several species of Heliconius butterfly are capable of incorporating these plant compounds as a form of chemical defense against predators. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.

<span class="mw-page-title-main">Cyanohydrin</span> Functional group in organic chemistry

In organic chemistry, a cyanohydrin or hydroxynitrile is a functional group found in organic compounds in which a cyano and a hydroxy group are attached to the same carbon atom. The general formula is R2C(OH)CN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids. Cyanohydrins can be formed by the cyanohydrin reaction, which involves treating a ketone or an aldehyde with hydrogen cyanide (HCN) in the presence of excess amounts of sodium cyanide (NaCN) as a catalyst:

<i>Prunus serotina</i> Species of tree

Prunus serotina, commonly called black cherry, wild black cherry, rum cherry, or mountain black cherry, is a deciduous tree or shrub of the genus Prunus. Despite being called black cherry, it is not very closely related to the commonly cultivated cherries such as sweet cherry, sour cherry and Japanese flowering cherries which belong to Prunus subg. Cerasus. Instead, P. serotina belongs to Prunus subg. Padus, a subgenus also including Eurasian bird cherry and chokecherry. The species is widespread and common in North America and South America.

<span class="mw-page-title-main">Mandelic acid</span> Chemical compound

Mandelic acid is an aromatic alpha hydroxy acid with the molecular formula C6H5CH(OH)CO2H. It is a white crystalline solid that is soluble in water and polar organic solvents. It is a useful precursor to various drugs. The molecule is chiral. The racemic mixture is known as paramandelic acid.

<span class="mw-page-title-main">Apigenin</span> Chemical compound

Apigenin (4′,5,7-trihydroxyflavone), found in many plants, is a natural product belonging to the flavone class that is the aglycone of several naturally occurring glycosides. It is a yellow crystalline solid that has been used to dye wool.

<span class="mw-page-title-main">Glycoside hydrolase</span> Class of enzymes which break glycosidic bonds via hydrolysis

In biochemistry, glycoside hydrolases are a class of enzymes which catalyze the hydrolysis of glycosidic bonds in complex sugars. They are extremely common enzymes, with roles in nature including degradation of biomass such as cellulose (cellulase), hemicellulose, and starch (amylase), in anti-bacterial defense strategies, in pathogenesis mechanisms and in normal cellular function. Together with glycosyltransferases, glycosidases form the major catalytic machinery for the synthesis and breakage of glycosidic bonds.

<span class="mw-page-title-main">Dhurrin</span> Chemical compound

Dhurrin is a cyanogenic glycoside produced in many plants. Discovered in multiple sorghum varieties in 1906 as the culprit of cattle poisoning by hydrogen cyanide, dhurrin is most typically associated with Sorghum bicolor, the organism used for mapping the biosynthesis of dhurrin from tyrosine. Dhurrin's name is derived from the Arabic word for sorghum.

<span class="mw-page-title-main">Lotaustralin</span> Chemical compound

Lotaustralin is a cyanogenic glucoside found in small amounts in Fabaceae austral trefoil, cassava, lima bean, roseroot and white clover, among other plants. Lotaustralin is the glucoside of methyl ethyl ketone cyanohydrin and is structurally related to linamarin, the acetone cyanohydrin glucoside also found in these plants. Both lotaustralin and linamarin may be hydrolyzed by the enzyme linamarase to form glucose and a precursor to the toxic compound hydrogen cyanide.

<span class="mw-page-title-main">Mandelonitrile lyase</span>

The enzyme (R)-mandelonitrile lyase (EC 4.1.2.10, (R)-HNL, (R)-oxynitrilase, (R)-hydroxynitrile lyase) catalyzes the chemical reaction

In enzymology, a hydroxymandelonitrile glucosyltransferase is an enzyme that catalyzes the chemical reaction

<span class="mw-page-title-main">Mandelonitrile</span> Chemical compound

In organic chemistry, mandelonitrile is the nitrile of mandelic acid, or the cyanohydrin derivative of benzaldehyde. Small amounts of mandelonitrile occur in the pits of some fruits.

Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful.

Tyrosine N-monooxygenase (EC 1.14.13.41, tyrosine N-hydroxylase, CYP79A1) is an enzyme with systematic name L-tyrosine,NADPH:oxygen oxidoreductase (N-hydroxylating). This enzyme catalyses the following chemical reaction

Isoleucine N-monooxygenase (EC 1.14.13.117, CYP79D3, CYP79D4) is an enzyme with systematic name L-isoleucine,NADPH:oxygen oxidoreductase (N-hydroxylating). This enzyme catalyses the following chemical reaction

(S)-hydroxynitrile lyase (EC 4.1.2.47, (S)-cyanohydrin producing hydroxynitrile lyase, (S)-oxynitrilase, (S)-HbHNL, (S)-MeHNL, hydroxynitrile lyase, oxynitrilase, HbHNL, MeHNL, (S)-selective hydroxynitrile lyase, (S)-cyanohydrin carbonyl-lyase (cyanide forming), hydroxynitrilase) is an enzyme with systematic name (S)-cyanohydrin lyase (cyanide forming). This enzyme catalyses the interconversion between cyanohydrins and the carbonyl compounds derived from the cyanohydrin with free cyanide, as in the following two chemical reactions:

<span class="mw-page-title-main">Benzyl gentiobioside</span> Chemical compound

Benzyl gentiobioside is a decyanogenated form of amygdalin. Benzyl gentiobioside occurs in Prunus persica seeds.

References

  1. 1 2 3 4 5 6 Sánchez-Pérez, Raquel; Belmonte, Fara Sáez; Borch, Jonas; Dicenta, Federico; Møller, Birger Lindberg; Jørgensen, Kirsten (April 2012). "Prunasin Hydrolases during Fruit Development in Sweet and Bitter Almonds". Plant Physiology. 158 (4): 1916–1932. doi:10.1104/pp.111.192021. ISSN   0032-0889. PMC   3320195 . PMID   22353576.
  2. ↑ Nahrstedt, Adolf; Rockenbach, Jürgen (1993). "Occurrence of the cyanogenic glucoside prunasin and II corresponding mandelic acid amide glucoside in Olinia species (oliniaceae)". Phytochemistry. 34 (2): 433. Bibcode:1993PChem..34..433N. doi:10.1016/0031-9422(93)80024-M.
  3. ↑ Andrew Pengelly (2004), The Constituents of Medicinal Plants (2nd ed.), Allen & Unwin, pp. 44–45, ISBN   978-1-74114-052-1
  4. 1 2 Miller, Rebecca E.; Gleadow, Roslyn M.; Woodrow, Ian E. (2004). "Cyanogenesis in tropical Prunus turneriana: characterisation, variation and response to low light". Functional Plant Biology. 31 (5): 491–503. doi:10.1071/FP03218. ISSN   1445-4408. PMID   32688921.
  5. 1 2 Thodberg, Sara; Del Cueto, Jorge; Mazzeo, Rosa; Pavan, Stefano; Lotti, Concetta; Dicenta, Federico; Jakobsen Neilson, Elizabeth H.; Møller, Birger Lindberg; Sánchez-Pérez, Raquel (November 2018). "Elucidation of the Amygdalin Pathway Reveals the Metabolic Basis of Bitter and Sweet Almonds (Prunus dulcis)1[OPEN]". Plant Physiology. 178 (3): 1096–1111. doi:10.1104/pp.18.00922. ISSN   0032-0889. PMC   6236625 . PMID   30297455.
  6. ↑ Sánchez-Pérez, Raquel; Jørgensen, Kirsten; Olsen, Carl Erik; Dicenta, Federico; Møller, Birger Lindberg (March 2008). "Bitterness in Almonds". Plant Physiology. 146 (3): 1040–1052. doi:10.1104/pp.107.112979. ISSN   0032-0889. PMC   2259050 . PMID   18192442.
  7. ↑ Neilson, Elizabeth H.; Goodger, Jason Q.D.; Motawia, Mohammed Saddik; Bjarnholt, Nanna; Frisch, Tina; Olsen, Carl Erik; Møller, Birger Lindberg; Woodrow, Ian E. (December 2011). "Phenylalanine derived cyanogenic diglucosides from Eucalyptus camphora and their abundances in relation to ontogeny and tissue type". Phytochemistry. 72 (18): 2325–2334. Bibcode:2011PChem..72.2325N. doi:10.1016/j.phytochem.2011.08.022. PMID   21945721.
  8. 1 2 Yamaguchi, Takuya; Yamamoto, Kazunori; Asano, Yasuhisa (September 2014). "Identification and characterization of CYP79D16 and CYP71AN24 catalyzing the first and second steps in l-phenylalanine-derived cyanogenic glycoside biosynthesis in the Japanese apricot, Prunus mume Sieb. et Zucc". Plant Molecular Biology. 86 (1–2): 215–223. doi:10.1007/s11103-014-0225-6. ISSN   0167-4412. PMID   25015725. S2CID   14884838.
  9. ↑ Zhou, Jiming; Hartmann, Stefanie; Shepherd, Brianne K.; Poulton, Jonathan E. (2002-07-01). "Investigation of the Microheterogeneity and Aglycone Specificity-Conferring Residues of Black Cherry Prunasin Hydrolases". Plant Physiology. 129 (3): 1252–1264. doi:10.1104/pp.010863. ISSN   0032-0889. PMC   166519 . PMID   12114579.
  10. 1 2 Hansen, Cecilie Cetti; Sørensen, Mette; Veiga, Thiago A.M.; Zibrandtsen, Juliane F.S.; Heskes, Allison M.; Olsen, Carl Erik; Boughton, Berin A.; Møller, Birger Lindberg; Neilson, Elizabeth H.J. (November 2018). "Reconfigured Cyanogenic Glucoside Biosynthesis in Eucalyptus cladocalyx Involves a Cytochrome P450 CYP706C55". Plant Physiology. 178 (3): 1081–1095. doi:10.1104/pp.18.00998. ISSN   0032-0889. PMC   6236593 . PMID   30297456.
  11. ↑ Pičmanová, Martina; Neilson, Elizabeth H.; Motawia, Mohammed S.; Olsen, Carl Erik; Agerbirk, Niels; Gray, Christopher J.; Flitsch, Sabine; Meier, Sebastian; Silvestro, Daniele; Jørgensen, Kirsten; Sánchez-Pérez, Raquel (2015-08-01). "A recycling pathway for cyanogenic glycosides evidenced by the comparative metabolic profiling in three cyanogenic plant species". Biochemical Journal. 469 (3): 375–389. doi:10.1042/BJ20150390. ISSN   0264-6021. PMID   26205491. S2CID   206152311.
  12. ↑ Diaz-Vivancos, Pedro; Bernal-Vicente, Agustina; Cantabella, Daniel; Petri, Cesar; Hern�ndez, Jos� Antonio (2017-12-01). "Metabolomics and Biochemical Approaches Link Salicylic Acid Biosynthesis to Cyanogenesis in Peach Plants". Plant and Cell Physiology. 58 (12): 2057–2066. doi: 10.1093/pcp/pcx135 . hdl: 10317/7678 . ISSN   0032-0781. PMID   29036663.
  13. ↑ Peter R. Cheeke (1989). Toxicants of Plant Origin: Glycosides. Vol. 2. CRC Press. p. 137.
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