Biosynthesis of the ipecac β-carboline alkaloid tubulosine

Bhakuni, D. S.; Jain, Sudha; Chaturvedi, Rekha

doi:10.1039/p19830001949

Cited by 4 publications

(9 citation statements)

References 5 publications

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“…These spectral features were similar to those of tubulosine (3), except for absence of the H-1′ signal, which appeared at δ 4.12 in 3, suggesting that 1 was the 1′,2′-dehydrogenated analogue of tubulosine (3). The proposed structure of 1 was consistent with its 13 C NMR spectrum, where C-1′ was observed at δ 166.4, instead of at δ 48.4 in 3. Finally, 1 was treated with NaBH 4 to afford 3 and isotubulosine (4).…”

supporting

confidence: 62%

“…The signals for a methoxyl group (δ 3.86) and two aromatic protons (δ 6.57 and 6.77) in its 1 H NMR spectrum, a NOESY correlation between OMe (δ 3.86) and H-8 (δ 6.57) which correlated with H-7, a fragment ion peak at m/z 230, 10 and its 13 C NMR spectrum (see Experimental Section) all suggested that 2 contained a 9-methoxy-10-hydroxybenzo[a]quinolizine moiety. Its 1 H NMR spectrum showed signals for a terminal vinyl group at δ 5.17, 5.23, and 5.60, signals for a hydroxymethyl group at δ 3.57 and 3.79, and a methine proton at δ 2.35.…”

mentioning

confidence: 98%

“…13 Alkaloid 1 could be derived from tubulosine (3) or isotubulosine (4). Two plausible mechanisms could be proposed for the formation of 3 and 4.…”

mentioning

confidence: 98%

“…It showed UV maxima at 225 and 285 nm and IR bands at 3569, 1613, and 1516 cm -1 . The signals for a methoxyl group (δ 3.86) and two aromatic protons (δ 6.57 and 6.77) in its 1 H NMR spectrum, a NOESY correlation between OMe (δ 3.86) and H-8 (δ 6.57) which correlated with H-7, a fragment ion peak at m/z 230, 10 and its 13 C NMR spectrum (see Experimental Section) all suggested that 2 contained a 9-methoxy-10-hydroxybenzo[a]quinolizine moiety. Its 1 H NMR spectrum showed signals for a terminal vinyl group at δ 5.17 The cis quinolizine ring junction was indicated by the absence of Bohlmann bands in its IR spectrum and the presence of a deshielded proton resonance at δ 4.07, attributed to H-11b.…”

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confidence: 99%

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Two Alangium Alkaloids from Alangium lamarckii

et al. 2000

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Two new Alangium alkaloids, 1',2'-dehydrotubulosine (1) and alangine (2), were isolated from the dried fruits of Alangium lamarckii along with tubulosine (3), isotubulosine (4), deoxytubulosine, cephaeline, isocephaeline, psychotrine, neocephaeline, 10-O-demethylcephaeline, 2'-N-(1"-deoxy-1" -beta-D-fructopyranosyl)cephaeline, protoemetine, protoemetinol, salsoline, and alangiside. The structures of the new alkaloids (1 and 2) were determined by spectroscopic and chemical means.

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supporting

confidence: 62%

mentioning

confidence: 98%

“…13 Alkaloid 1 could be derived from tubulosine (3) or isotubulosine (4). Two plausible mechanisms could be proposed for the formation of 3 and 4.…”

mentioning

confidence: 98%

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confidence: 99%

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Two Alangium Alkaloids from Alangium lamarckii

et al. 2000

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“…In Alangium, the related alkaloid tubulosine, which has a ␤-carboline skeleton instead of the second tetrahydroisoquinoline moiety of emetine, has also been demonstrated to be synthesized from N-deacetylisoipecoside (33,34). In contrast, the 1␤(R)-epimer N-deacetylipecoside is the precursor mainly of ipecoside and alangiside, the alkaloidal glucosides having a ␤-configuration.…”

Section: Discussionmentioning

confidence: 99%

The New β-D-Glucosidase in Terpenoid-Isoquinoline Alkaloid Biosynthesis in Psychotria ipecacuanha

Nomura

Quesada

Kutchan

2008

Journal of Biological Chemistry

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Ipecac alkaloids produced in the medicinal plant Psychotria ipecacuanha such as emetine and cephaeline possess a monoterpenoid-tetrahydroisoquinoline skeleton, which is formed by condensation of dopamine and secologanin. Deglucosylation of one of the condensed products N-deacetylisoipecoside (1␣(S)-epimer) is considered to be a part of the reactions for emetine biosynthesis, whereas its 1␤(R)-epimer N-deacetylipecoside is converted to ipecoside in P. ipecacuanha. Here, we isolated a cDNA clone Ipeglu1 encoding Ipecac alkaloid ␤-D-glucosidase from P. ipecacuanha. The deduced protein showed 54 and 48% identities to raucaffricine ␤-glucosidase and strictosidine ␤-glucosidase, respectively. Recombinant IpeGlu1 enzyme preferentially hydrolyzed glucosidic Ipecac alkaloids except for their lactams, but showed poor or no activity toward other substrates, including terpenoid-indole alkaloid glucosides. Liquid chromatography-tandem mass spectrometry analysis of deglucosylated products of N-deacetylisoipecoside revealed spontaneous transitions of the highly reactive aglycons, one of which was supposed to be the intermediate for emetine biosynthesis. IpeGlu1 activity was extremely poor toward 7-Omethyl and 6,7-O,O-dimethyl derivatives. However, 6-O-methyl derivatives were hydrolyzed as efficiently as non-methylated substrates, suggesting the possibility of 6-O-methylation prior to deglucosylation by IpeGlu1. In contrast to the strictosidine ␤-glucosidase that stereospecifically hydrolyzes 3␣(S)-epimer in terpenoid-indole alkaloid biosynthesis, IpeGlu1 lacked stereospecificity for its substrates where 1␤(R)-epimers were preferred to 1␣(S)-epimers, although ipecoside (1␤(R)) is a major alkaloidal glucoside in P. ipecacuanha, suggesting the compartmentalization of IpeGlu1 from ipecoside. These facts have significant implications for distinct physiological roles of 1␣(S)-and 1␤(R)-epimers and for the involvement of IpeGlu1 in the metabolic fate of both of them.

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