Kováts indices diterpene hydrocarbons on fused-silica capillary columns

Nortriketones: Antimicrobial Trimethylated Acylphloroglucinols from Ma̅nuka (Leptospermum scoparium)

Four trimethylated acylphloroglucinols (5-8) have been isolated from ma̅nuka (Leptospermum scoparium) foliage. Apart from myrigalone A (8), which has previously been isolated from European bog myrtle (Myrica gale), these compounds have not been characterized before. The nortriketones are structurally similar to the bioactive tetramethylated β-triketones from ma̅nuka, but have one less ring methyl group. Two oxidized trimethylated compounds, 9 and 10, were also isolated, but these are likely isolation artifacts. When evaluated for antibacterial activity against Gram-positive bacteria, myrigalone A (8) was slightly less potent (MIC 64 μg/mL) than the corresponding tetramethylated compound, grandiflorone (4) (MIC 16-32 μg/mL). Unlike their tetramethylated analogues, the nortriketones were inactive against the herbicide target enzyme p-hydroxyphenylpyruvate dioxygenase. The Raman spectra of leaf oil glands in different ma̅nuka varieties can be used to distinguish plants that contain nortriketones from those that accumulate triketones.

Analysis of the equations for the temperature dependence of the retention index. II. Physico-chemical meaning of the parameters

A general expression for the meaning of various parameters from the retention index-temperature equations was found. This is a linear combination of two solute dependent factors consisting of differences of enthalpies and respective entropies of solution, between the solute and the reference inferior n-alkane. The particular coefficients for each parameter are stationary phase dependent factors. They were calculated from methylene contributions to the thermodynamic functions of solution in SE-30 and Carbowax-20M, revealing the influence of the used temperature range. A short review of structural influences on dI/dT is included.