title: Fragmentation patterns of newly isolated cassane butenolide diterpenes and differentiation of stereoisomer by tandem mass spectrometry.
abstract: Different stereoisomers of active molecules often cause different physiological responses and hence pose a challenge for their identification. This study involves perceptive fragmentation behavior of newly isolated cassane butenolides, caesalpinolide A [1] and caesalpinolide B [2] (epimeric at the hemiketal position) by tandem MS. The electrospray ionization-mass spectrometry (ESI-MS)/collision-induced dissociation (CID; ESI-MS(2) and ESI-IT-MS(n)) were investigated. The effect of orientations of hemiketal hydroxyl at C-12 was clearly observed in the mass spectrum. Tandem mass spectra of 1, 1(A) or 2, 2(A) show stereospecific fragmentation resulting in significant abundance dissimilarity of [MH - H(2)O](+) as well as differences in fragmentation pathway. Both of these pathways seem to be influenced by the stereochemistry of the molecule. The differentiation can be clearly visualized from the [M + H - H(2)O](+)/[M + H](+) ratio of the two isomers where beta-isomer 2 was found to be five times higher than that of alpha-isomer 1 in full scan liquid chromatography-electrospray ionization mass spectrometry(LC-ESI-MS). In high-energy CID, the mass fingerprint of 1, 2, 1(A), and 2(A) was found to be different from one another.
authors.affiliation: Sophisticated Analytical Instrument Facility, Central Drug Research Institute, Lucknow-226001, India. s_kanojiya@rediffmail.com
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Kanojiya
authors.forename: Prem P
authors.initials: PP
authors.lastname: Yadav
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D029911:Caesalpinia / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry; D004224:Diterpenes / Q000032:analysis*; D006859:Hydrogen / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry; D014867:Water / Q000737:chemistry
chemical_list: D004224:Diterpenes; D014867:Water; D006859:Hydrogen; D003903:Deuterium; D019342:Acetic Acid