Biosynthesis of 20-hydroxyecdysone in plants: 3β-Hydroxy-5β-cholestan-6-one as an intermediate immediately after cholesterol in Ajuga hairy roots

Fujimoto, Yoshinori; Maeda, Izumi; Ohyama, Kiyoshi; Hikiba, Juri; Kataoka, Hiroshi

doi:10.1016/j.phytochem.2014.12.019

Cited by 10 publications

(8 citation statements)

References 22 publications

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“…We had previously used 26,26,26,27,27,27- d 6 -chol to prepare our standards, which was synthesized using the method of Holm and Crossland, with a (optimal) 7% yield over nine steps. To our knowledge, the only other synthesis of chol-26,26,26,27,27,27- d 6 uses an expensive desmosterol starting material. , We therefore opted to develop a synthesis of 17,20,21,21,21,22- d 6 -chol ( 8 ), which was achieved in six steps from pregnenolone with an overall yield of 32% (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…Given that the computed rates of H-atom abstraction from, and peroxyl radical addition to, chol were similar, we wondered whether tunneling in the HAT pathway is responsible for the predominance of hydroperoxides over epoxides in cholesterol autoxidations. Expecting this to be revealed by a large kinetic isotope effect (KIE) on the HAT, we synthesized 2,2,4,4,7,7- d 6 -cholesterol ( 9 , 2,2,4,4,7,7- d 6 -chol) by the method of Fujimoto et al and carried out autoxidations analogous to those described above. Amazingly, the product distribution observed in the 2,2,4,4,7,7- d 6 -chol autoxidations was completely inverted compared to that observed in the chol autoxidations, such that the epoxides accounted for over 75% of the product mixture.…”

Section: Resultsmentioning

confidence: 99%

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H-Atom Abstraction vs Addition: Accounting for the Diverse Product Distribution in the Autoxidation of Cholesterol and Its Esters

Zielinski

Pratt

2019

J. Am. Chem. Soc.

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We recently communicated that the free-radical-mediated oxidation (autoxidation) of cholesterol yields a more complex mixture of hydroperoxide products than previously appreciated. In addition to the epimers of the major product, cholesterol 7-hydroperoxide, the epimers of each of the regioisomeric 4- and 6-hydroperoxides are formed as is the 5α-hydroperoxide in the presence of a good H-atom donor. Herein, we complete the story by reporting the products resulting from competing peroxyl radical addition to cholesterol, the stereoisomeric cholesterol-5,6-epoxides, which account for 12% of the oxidation products, as well as electrophilic dehydration products of the cholesterol hydroperoxides, 4-, 6-, and 7-ketocholesterol. Moreover, we interrogate how their distributionand abundance relative to the H-atom abstraction productschanges in the presence of good H-atom donors, which has serious implications for how these oxysterols are used as biomarkers. The resolution and quantification of all autoxidation products by LC-MS/MS was greatly enabled by the synthesis of a new isotopically labeled cholesterol standard and corresponding selected autoxidation products. The autoxidation of cholesteryl acetate was also investigated as a model for the cholesterol esters which abound in vivo. Although esterification of cholesterol imparts measurable stereoelectronic effects, most importantly reflected in the fact that it autoxidizes at 4 times the rate of unesterified cholesterol, the product distribution is largely similar to that of cholesterol. Deuteration of the allylic positions in cholesterol suppresses autoxidation by H-atom transfer (HAT) in favor of addition, such that the epoxides are the major products. The corresponding kinetic isotope effect (k H/k D ∼ 20) indicates that tunneling underlies the preference for the HAT pathway.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

H-Atom Abstraction vs Addition: Accounting for the Diverse Product Distribution in the Autoxidation of Cholesterol and Its Esters

Zielinski

Pratt

2019

J. Am. Chem. Soc.

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“…While considerable progress has recently been made in elucidating the later stages of ecdysteroid biosynthesis from dietary cholesterol or a related sterol in insects and other arthropods, understanding of the biosynthetic pathway(s) and the regulation in plants is still largely unknown. The current state of knowledge has been reviewed (Fujimoto et al 2000(Fujimoto et al , 2015Dinan 2001). Very briefly, plants are capable of generating sterols and steroids de novo by the cytosolic mevalonic acid (MVA) or plastidial methylerythritol phosphate (MEP) routes, although the mevalonate pathway seems to predominate in the biosynthesis of ecdysteroids.…”

Section: Biosynthesis In Plantsmentioning

confidence: 99%

Dietary Phytoecdysteroids

Dinan¹,

Mamadalieva²,

Lafont³

2019

Handbook of Dietary Phytochemicals

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“…It was recently proposed that 3β-hydroxy-5β-cholestan-6-one (5β-ketone) was involved in 20HE biosynthesis in the hairy roots of Ajuga reptans var. atropurpurea (Lamiaceae) (Fujimoto et al 2015). Cholesterol was converted to the 5β-ketone with the migration of hydrogen from the C-6 to the C-5 position.…”

Section: Introductionmentioning

confidence: 99%

“…These findings, along with the previous observation that the ketone was efficiently converted to 20-hydroxyecdysone, strongly suggest that the 5β-ketone is an intermediate immediately formed after cholesterol during 20-hydroxyecdysone biosynthesis in Ajuga sp. (Fujimoto et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Transcriptome analysis of abscisic acid induced 20E regulation in suspension Ajuga lobata cells

2018

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D. Don is a medicinal plant rich in 20-hydroxyecdysone (20E), alkaloids, and other active substances. In this study, the cell suspension was incubated for 7 days, followed by the analysis on the effects of abscisic acid (ABA) on the regulation of 20E synthesis. Then suspension cells treated with 0.15 mg/l ABA were used as material, with the Illumina technology applied for transcriptome sequencing. Digital analysis on the gene expression profile was carried out on ABA treated and control samples, respectively. Finally, transcriptomics was applied to assess the molecular response of induced by ABA through applying transcriptomics by evaluating differentially expressed genes. The results suggested that ABA promoted 20E accumulation, while longer processing time caused cell browning. A total of 154 genes were significantly regulated after ABA treatment, with 99 up-regulated and 55 down-regulated, respectively. In addition to 20E-related pathways, the genes belonged to the ko00900 (terpenoid backbone biosynthesis) pathway (six differentially expressed genes [DEGs]), ko00100 (steroid biosynthesis) pathway (four DEGs), and ko00140 (steroid hormone biosynthesis) pathway (six DEGs). Providing a better understanding of the 20E biosynthetic pathway and its regulation, in particular in plants, this study is necessary.

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Biosynthesis of 20-hydroxyecdysone in plants: 3β-Hydroxy-5β-cholestan-6-one as an intermediate immediately after cholesterol in Ajuga hairy roots

Cited by 10 publications

References 22 publications

H-Atom Abstraction vs Addition: Accounting for the Diverse Product Distribution in the Autoxidation of Cholesterol and Its Esters

H-Atom Abstraction vs Addition: Accounting for the Diverse Product Distribution in the Autoxidation of Cholesterol and Its Esters

Dietary Phytoecdysteroids

Transcriptome analysis of abscisic acid induced 20E regulation in suspension Ajuga lobata cells

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