Very-long-chain 1,2-and 1,3-bifunctional compounds from the cuticular wax of Cosmos bipinnatus petals

Four uncommon classes of very-long-chain compounds were identified and quantified in the petal wax of Cosmos bipinnatus (Asteraceae). The first two were homologous series of alkane 1,2-diols and 1,3-diols, both ranging from C-20 to C-26. The upper and lower petal surfaces contained 0.11 and 0.09 mu g/cm(2) of 1,2-diols, respectively. 1,3-Diols were present at quantities one order of magnitude less than the 1,2-diols. Both series had similar chain length distributions, with 6-20%, 59-73% and 20-31% of the C-20, C-22 and C-24 diols, respectively. The other two compound classes were primary and secondary monoacetates of C-20-C-24 1,2-diols. The monoacetates had chain length profiles similar to the free 1,2-diols, and amounted to 0.04 and 0.09 mu g/cm(2) on the adaxial and abaxial sides, respectively. Methods were developed to minimize acyl migration during monoacetate isomer analyses. The ratios of diol 1-acetates to dial 2-acetates averaged close to 3:5, and thus opposite to the chemical equilibrium ratio of 7:3. (C) 2012 Elsevier Ltd. All rights reserved.