Shape Selectivity of C₃₀ Phases for RP-HPLC Separation of Tocopherol Isomers and Correlation with MAS NMR Data from Suspended Stationary Phases

Abstract

Vitamin E (tocopherol) acts in various organisms as the main free radical scavenger. This capacity, which is enhanced by the synergetic effect of vitamin C and carotenes, points to a possible application as anti-tumor agent in chemotherapy. There are several isomeric forms, namely alpha-, beta-, gamma-, and delta-tocopherol, having different antioxidative abilities, with alpha-tocopherol being the most biologically active. Using methanol as eluent and a C30 stationary phase, we achieved complete separation of alpha-, beta-, gamma-, and delta-tocopherol and alpha-tocopherol acetate by RP-HPLC within 14 min. Detection was performed by UV and 1H NMR spectroscopy. The advantage of NMR is the possibility of structural identification of chromatographic peaks. Also, coeluting peaks are easily recognized. The enhanced shape recognition of the C30 phase has been attributed to the high order of the alkyl chains of the stationary phase. This has, so far, been proven by solid-state NMR spectroscopy. We now introduce the technique of 13C MAS NMR spectroscopy of suspended stationary phases. The resulting NMR spectra reveal that, in the presence of weak eluents, like methanol, the overall high order of the C30 chains is slightly altered, whereas in stronger eluents, like MTBE, the alkyl chains possess a higher mobility.

Simultaneous Determination of Tocotrienols, Tocopherols, Retinol, and Major Carotenoids in Human Plasma

“…Nevertheless, it is not suitable for the simultaneous determination of tocopherols (23 ). Likewise, the use of nuclear magnetic resonance for tocopherol isomer analysis is limited by its low sensitivity (24 ). No single method exists that can simultaneously analyze tocotrienols, tocopherols, retinol, and carotenoids in biological samples.…”

Cupaniol, a New Branched Polyprenol, from Cupania latifolia

“…5. In addition to cupaniol, ficaprenol 12, 14,15) a-and b-tocopherols, 16) b-amyrin, 17) and taraxerol 17) were isolated from the AcOEt-soluble fraction and characterized by comparing the NMR and MS data with the reported values, while (Ϫ)-epicatechin 18,19) and proanthocyanidin A2 20) were isolated from the AcOEt-insoluble fraction of the MeOH extract.…”

Critical investigation of coupled liquid chromatography–NMR spectroscopy in pharmaceutical impurity identification

“…Certain approaches such as gradient LC methods can be useful in this respect, and some chromatographic phases have been shown to cope well with increased loading. 8 However, method redevelopment takes time, during which material could simply be isolated by preparative LC. This has to be taken into account when thinking of overall efficiency.…”