Differentiation of three pairs of aconite alkaloid isomers from Aconitum nagarum var. lasiandrum by electrospray ionization tandem mass spectrometry.[Pubmed: 16331739]

Three pairs of isomers of aconite alkaloids from Aconitum nagarum var. lasiandrum have been investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) employing ion-trap and quadrupole time-of-flight mass spectrometers in positive mode. Based on the differences of their fragmentation pathways and special fragment ions, three pairs of isomers of aconite alkaloids were differentiated. In addition, fragmentation laws of some veatchines and the discrepancy of fragmentation mechanisms between veatchine-type and aconitine-type alkaloid were also concluded. In the case of veatchines, a radical would be formed by homolysis of C18--C4 or C18--H bonds, followed by elimination of a series of C(2)H(2) and C(2)H(4). Moreover, the retro-Diels-Alder (RDA) reaction occurred in the E-ring and double-electron transfer triggered by the positive charge on C1 led to the formation of diagnostic ions at m/z 216. With regard to aconitine-type alkaloids, the N-substituent is not eliminated easily. Although there is no carbonyl group on some aconitine-type alkaloids, with hydroxyl and methoxyl on C15 and C16 respectively, CO was readily eliminated through tautomerization.

Three new diterpene alkaloids from the roots of Aconitum nagarum var. lasiandrum.[Pubmed: 16320214]

Three new diterpene alkaloids, 16,17-dihydro-12 beta,16 beta-epoxynapelline (1), N-deethyl- N-methyl-12-epi-napelline (2) and 11- epi-16 alpha,17-dihydroxylepenine (3), along with twenty-six known alkaloids (4 - 29) were isolated from the roots of Aconitum nagarum var. lasiandrum. The chemical structures of the new compounds were established by HR-MS as well as 1D- and 2D-NMR spectroscopic analysis. The absolute stereochemistry of 1 was confirmed by X-ray crystallography.