Nonan-2-ol esters in sorghum leaf epicuticular wax and their collection by preparative gas chromatography

Abstract

Epicuticular wax from sorghum seedling leaves was isolated and analyzed by TLC and GC. Its composition was remarkably similar to that of waxes on many other Gramineae leaves with the exception that three alkan-2-ol esters (nonan-2-ol docosanoate, nonan-2-ol tetracosanoate, and nonan-2-ol hexacosanoate) were present. This was unexpected as such esters have hitherto only been reported in waxes of plants with the capability of synthesizing 13-diketone lipids. The C~,-C~s alkan-2-ol esters were separated from the C~s-C~ alkan-1-ol esters by preparative GC.The column effluent was passed through a small Dexsil-300 trap maintained at 150 ~ and the esters eluted therefrom with chloroform. This technique gave better than 90% recovery of a [1-"C]-C~. ester. INTRODUCI'IONDisclosing the I~-diketone (primarily, hentriacontan-14,16-dione and 25-hydroxyhentriacontan-14,16-dione) and esterified alkan-2-ol (primarily tridecan-2-ol and pentadecan-2-ol) biosynthetic pathways and their genetic control is our primary goal. As biological material we have used barley spikes of the eceriferum mutants which determine synthesis and deposition of the very long chain lipids on the external surface of epidermal cell walls. Since large amounts of material would spur attempts to isolate the enzymes involved, we have been looking for a plant which synthesizes one or more of the specified lipids on rapidly growing seedling leaves. Herein we identify nonan-2-ol Abbreviations: GC = gas chromatography; MS = mass spectrometry; TLC = thin layer chromatography: TMS = trimethylsilyl.Springer-Verlag

Cuticle characteristics and volatile emissions of petals in Antirrhinum majus

“…Whereas branched alkanes comprise 23.6% to 27.8% of snapdragon petal waxes, in petals of these other species branched alkanes range from 0.01% to less than 2% of total petal wax. Although alkan‐2‐ol esters have been reported in Eucalyptus species and Sorghum bicolor L. Moench leaf waxes and Hordeum vulgare L. (barley) stem waxes (Horn et al 1964, Wettstein‐Knowles and Netting 1976, Wettstein‐Knowles and Mikkelsen 1984, Walton 1990), we are unaware of any reports of plant alkan‐2‐ol esters with a hydroxy group as described here for snapdragon petal waxes. What ecological significance these unique petal lipids have is as yet unknown.…”

TheCer-cqugene cluster determines three key players in a β-diketone synthase polyketide pathway synthesizing aliphatics in epicuticular waxes

“…As in barley, the β-diketones in three Agropyron species are accompanied by esterified 2-ols (primarily C 13 and C 15 ) ( Tulloch, 1983 ). In the absence of β-diketones, short esterified alkan-2-ols occur in sorghum leaf waxes (C 9 ) and in some Papaver fruit capsule waxes (C 11 –C 17 ) ( von Wettstein-Knowles et al , 1984 ; Jetter and Riederer, 1996 ). With the exception of the Papaver waxes the above observations suggest an intimate biochemical relationship between β-diketone aliphatics and esterified alkan-2-ols.…”

Identification of In-Chain-Functionalized Compounds and Methyl-Branched Alkanes in Cuticular Waxes of Triticum aestivum cv. Bethlehem

“…2-Alkanol esters have been identified in several grass species, typically as minor components associated with the much more prominent wax β-diketones [30,55,56]. Most previous analyses revealed only esters of 2-alkanols bearing no other functional groups, except for one report identifying 7-oxo-pentadecan-2-ol as a minor constituent of barley spike wax [45].…”