- Photogeneration of an o-quinone methide from pyridoxine (vitamin B6) in aqueous solution
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Photolysis (254, 266 or 308 nm) of pyridoxine (vitamin B6) in aqueous solution gives an o-quinone methide efficiently which is trapped by MeOH and ethyl vinyl ether.
- Brousmiche, Darryl,Wan, Peter
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- Quantification of a botanical negative marker without an identical standard: Ginkgotoxin in Ginkgo biloba
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A new strategy for the analysis of natural products uses a combination of quantitative 1H NMR (qHNMR) and adsorbent-free countercurrent separation (CS) methodology to establish a quantification method for ginkgotoxin (4′-O-methylpyridoxine) in Ginkgo biloba preparations. The target analyte was concentrated in a one-step CS process using the ChMWat +2 solvent system (CHCl3-MeOH-H2O, 10:5:5) and subsequently assayed by qHNMR. While commercial G. biloba seeds contained 59 μg of ginkgotoxin per seed, the compound was below the limit of detection (9 ppm) in a typical leaf extract. Due to the enrichment potential and loss-free operation of CS, the combination of CS and qHNMR is a generally suitable approach for threshold assays aimed at quantifying target compounds such as botanical negative markers at the low ppm level. As the proof of principle is demonstrated for relatively small CS capacities (20 mL, 1:40 loading) and modest NMR sensitivity (n = 16, 400 MHz, 5 mm RT probe), the approach can be adapted to quantification at the ppb level. The procedure enables the quantification of a botanical negative marker in the absence of identical reference material, which otherwise is a prerequisite for LC-based assays.
- Liu, Yang,Chen, Shao-Nong,McAlpine, James B.,Klein, Larry L.,Friesen, J. Brent,Lankin, David C.,Pauli, Guido F.
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- A regioselective etherification of pyridoxine via an ortho-pyridinone methide intermediate
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The catalyst-free, regioselective synthesis of 4′-O-substituted pyridoxine derivatives under solventless conditions is described. The methodology relies on the highly regioselective formation of the ortho-pyridinone methide from pyridoxine and subsequent oxa-Michael addition of alcohol nucleophiles. This methodology provides good to excellent yields for primary and secondary alcohols and moderate yields for tertiary alcohols.
- Yazarians, Jessica A.,Jiménez, Brian L.,Boyce, Gregory R.
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