Isolation and identification of oligomers from partial degradation of lime fruit cutin.
Complementary degradative treatments with low-temperature hydrofluoric acid and methanolic potassium hydroxide have been used to investigate the protective biopolymer cutin from Citrus aurantifolia (lime) fruits, augmenting prior enzymatic and chemical strategies to yield a more comprehensive view of its molecular architecture. Analysis of the resulting soluble oligomeric fragments with one- and two-dimensional NMR and MS methods identified a new dimer and three trimeric esters of primary alcohols based on 10,16-dihydroxyhexadecanoic acid and 10-oxo-16-hydroxyhexadecanoic acid units. Whereas only 10-oxo-16-hydroxyhexadecanoic acid units were found in the oligomers from hydrofluoric acid treatments, the dimer and trimer products isolated to date using diverse degradative methods included six of the seven possible stoichiometric ratios of monomer units. A novel glucoside-linked hydroxyfatty acid tetramer was also identified provisionally, suggesting that the cutin biopolymer can be bound covalently to the plant cell wall. Although the current findings suggest that the predominant molecular architecture of this protective polymer in lime fruits involves esters of primary and secondary alcohols based on long-chain hydroxyfatty acids, the possibility of additional cross-linking to enhance structural integrity is underscored by these and related findings of nonstandard cutin molecular architectures.
Tian
Shiying
S
Department of Chemistry, College of Staten Island, City University of New York Graduate Center and Institute for Macromolecular Assemblies, New York, New York 10031, USA.
Fang
Xiuhua
X
Wang
Weimin
W
Yu
Bingwu
B
Cheng
Xiaofang
X
Qiu
Feng
F
Mort
Andrew J
AJ
Stark
Ruth E
RE
D001704:Biopolymers / Q000737:chemistry* / Q000302:isolation & purification*; D002957:Citrus / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry*; D006858:Hydrofluoric Acid / Q000737:chemistry; D006878:Hydroxides / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry* / Q000302:isolation & purification*; D010936:Plant Extracts / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry
D001704:Biopolymers; D006878:Hydroxides; D008563:Membrane Lipids; D010936:Plant Extracts; D017680:Potassium Compounds; C000521:cutin; D006858:Hydrofluoric Acid; C029943:potassium hydroxide