NOESY on neurotoxins: NMR and conformational assignments of picrotoxins

Abstract

Nuclear Overhauser effect spectroscopy (NOESY) gave full assignments of the 1H‐NMR spectra of the picrotoxane neurotoxins tutin, hyenanchin, picrotoxinin and picrotin, as well as the solution conformations of these compounds, consistent with molecular modelling. Fully assigned 13C‐NMR data are reported. Copyright © 2001 John Wiley & Sons, Ltd.

Sweet Poisons: Honeys Contaminated with Glycosides of the Neurotoxin Tutin

“…In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet. 18 Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5. There were no other tutin glycosides detectable by 1 H NMR spectroscopy in the other RPLC fractions, and the NMR spectra of the two glycosides fully explained the NMR spectrum of the crude tutin glycoside fraction.…”

“…In order to maximize the chance of detecting tutin conjugates, we first wanted to separate them from the bulk of honey sugars and from tutin itself. Reversed-phase C 18 (RP) fractionation of toxic honeys analyzed by 1 H NMR spectroscopy showed that most of the sugars eluted in the first water fraction, and then there were two fractions, fraction B (10–20% acetonitrile in water) and fraction C (30–40% acetonitrile in water), in which the typical tutin methyl signals at 1.25 and 1.75 ppm could be detected. RP LC-MS analysis showed that tutin was the major component in the C fractions, but just a minor component in the B fractions (Table ).…”

“…The 1 H NMR spectrum of the latter fraction showed two main sets of tutin-type signals, in a ratio of about 1:1. In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet . Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5 .…”

“…High-resolution mass spectra were obtained on a Bruker microTOFQ mass spectrometer. A reference sample of tutin was isolated as previously described, and hyenanchin was isolated from fruits of Hyaenanche globosa by similar methods.…”

Sweet Poisons: Honeys Contaminated with Glycosides of the Neurotoxin Tutin

“…In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet. 18 Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5. There were no other tutin glycosides detectable by 1 H NMR spectroscopy in the other RPLC fractions, and the NMR spectra of the two glycosides fully explained the NMR spectrum of the crude tutin glycoside fraction.…”

“…In order to maximize the chance of detecting tutin conjugates, we first wanted to separate them from the bulk of honey sugars and from tutin itself. Reversed-phase C 18 (RP) fractionation of toxic honeys analyzed by 1 H NMR spectroscopy showed that most of the sugars eluted in the first water fraction, and then there were two fractions, fraction B (10–20% acetonitrile in water) and fraction C (30–40% acetonitrile in water), in which the typical tutin methyl signals at 1.25 and 1.75 ppm could be detected. RP LC-MS analysis showed that tutin was the major component in the C fractions, but just a minor component in the B fractions (Table ).…”

“…The 1 H NMR spectrum of the latter fraction showed two main sets of tutin-type signals, in a ratio of about 1:1. In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet . Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5 .…”

“…High-resolution mass spectra were obtained on a Bruker microTOFQ mass spectrometer. A reference sample of tutin was isolated as previously described, and hyenanchin was isolated from fruits of Hyaenanche globosa by similar methods.…”

Picrotoxane sesquiterpenoids: chemistry, chemo- and bio-syntheses and biological activities

“…Furthermore, dendrobine decreased the depolarisations of primary afferent neuron terminals induced by b-alanine and taurine and had no effect on GABA and glycine-induced depolarisations, which implied that the effects of dendrobine showed a closer resemblance to strychnine than to picrotoxinin. The research results for GABAergic transmission through neurons were signicantly different for tutin (18), coriamyrtin (17), and dihydrotutin (21), and the structure-activity relationship revealed that the presence of 5,3-g-lactone and 6-hydroxyl group, as well as the 4-isopropenyl moiety, were essential for the inhibitory activities, whereas the 2-hydroxyl group was not decisive. 39 GABA receptor antagonists include structurally quite distinct compounds (such as a-endosulphan, lindane, pronil, and picrotoxinin), and surprisingly, these small molecules appear to bind to the same site.…”

Sweet Poisons: Honeys Contaminated with Glycosides of the Neurotoxin Tutin

“…In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet. 18 Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5. There were no other tutin glycosides detectable by 1 H NMR spectroscopy in the other RPLC fractions, and the NMR spectra of the two glycosides fully explained the NMR spectrum of the crude tutin glycoside fraction.…”

“…In order to maximize the chance of detecting tutin conjugates, we first wanted to separate them from the bulk of honey sugars and from tutin itself. Reversed-phase C 18 (RP) fractionation of toxic honeys analyzed by 1 H NMR spectroscopy showed that most of the sugars eluted in the first water fraction, and then there were two fractions, fraction B (10–20% acetonitrile in water) and fraction C (30–40% acetonitrile in water), in which the typical tutin methyl signals at 1.25 and 1.75 ppm could be detected. RP LC-MS analysis showed that tutin was the major component in the C fractions, but just a minor component in the B fractions (Table ).…”

“…The 1 H NMR spectrum of the latter fraction showed two main sets of tutin-type signals, in a ratio of about 1:1. In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet . Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5 .…”

“…High-resolution mass spectra were obtained on a Bruker microTOFQ mass spectrometer. A reference sample of tutin was isolated as previously described, and hyenanchin was isolated from fruits of Hyaenanche globosa by similar methods.…”

Picrotoxane sesquiterpenoids: chemistry, chemo- and bio-syntheses and biological activities

“…Furthermore, dendrobine decreased the depolarisations of primary afferent neuron terminals induced by b-alanine and taurine and had no effect on GABA and glycine-induced depolarisations, which implied that the effects of dendrobine showed a closer resemblance to strychnine than to picrotoxinin. The research results for GABAergic transmission through neurons were signicantly different for tutin (18), coriamyrtin (17), and dihydrotutin (21), and the structure-activity relationship revealed that the presence of 5,3-g-lactone and 6-hydroxyl group, as well as the 4-isopropenyl moiety, were essential for the inhibitory activities, whereas the 2-hydroxyl group was not decisive. 39 GABA receptor antagonists include structurally quite distinct compounds (such as a-endosulphan, lindane, pronil, and picrotoxinin), and surprisingly, these small molecules appear to bind to the same site.…”

Sweet Poisons: Honeys Contaminated with Glycosides of the Neurotoxin Tutin

“…In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet. 18 Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5. There were no other tutin glycosides detectable by 1 H NMR spectroscopy in the other RPLC fractions, and the NMR spectra of the two glycosides fully explained the NMR spectrum of the crude tutin glycoside fraction.…”

“…In order to maximize the chance of detecting tutin conjugates, we first wanted to separate them from the bulk of honey sugars and from tutin itself. Reversed-phase C 18 (RP) fractionation of toxic honeys analyzed by 1 H NMR spectroscopy showed that most of the sugars eluted in the first water fraction, and then there were two fractions, fraction B (10–20% acetonitrile in water) and fraction C (30–40% acetonitrile in water), in which the typical tutin methyl signals at 1.25 and 1.75 ppm could be detected. RP LC-MS analysis showed that tutin was the major component in the C fractions, but just a minor component in the B fractions (Table ).…”

“…The 1 H NMR spectrum of the latter fraction showed two main sets of tutin-type signals, in a ratio of about 1:1. In particular there were two prominent singlets in the 4.0 to 4.3 ppm region, where H-2 of tutin occurs as a singlet . Preparative RPLC of this fraction, which required much care because of the weak UV absorption and the similar retention times of the peaks (9.00 and 9.35 min), led to the isolation of two tutin derivatives: glycosides 4 and 5 .…”

“…High-resolution mass spectra were obtained on a Bruker microTOFQ mass spectrometer. A reference sample of tutin was isolated as previously described, and hyenanchin was isolated from fruits of Hyaenanche globosa by similar methods.…”

Picrotoxane sesquiterpenoids: chemistry, chemo- and bio-syntheses and biological activities

“…Furthermore, dendrobine decreased the depolarisations of primary afferent neuron terminals induced by b-alanine and taurine and had no effect on GABA and glycine-induced depolarisations, which implied that the effects of dendrobine showed a closer resemblance to strychnine than to picrotoxinin. The research results for GABAergic transmission through neurons were signicantly different for tutin (18), coriamyrtin (17), and dihydrotutin (21), and the structure-activity relationship revealed that the presence of 5,3-g-lactone and 6-hydroxyl group, as well as the 4-isopropenyl moiety, were essential for the inhibitory activities, whereas the 2-hydroxyl group was not decisive. 39 GABA receptor antagonists include structurally quite distinct compounds (such as a-endosulphan, lindane, pronil, and picrotoxinin), and surprisingly, these small molecules appear to bind to the same site.…”