31-Norcycloartanol Fatty Acid Esters: Cholesteric Liquid Crystals from a Triterpene of Plant Origin

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Abstract
The triterpene 31-norcycloartanol, previously reported present in pollen of Taraxacum den leonis, was isolated from the ester fraction but not the free sterol fraction, of lipid extracts of this pollen. Even chain esters of this triterpene from the acetate to the palmitate were found to be mesomorphic. The acetate, butyrate, hexanoate and octanoate formed only a cholesteric mesophase while the decanoate, laurate, myristate and palmitate formed both smectic and cholesteric mesophases. Only the palmitate ester could be specifically detected by gas-liquid chromatography in the naturally occurring fraction, but the probability of other liquid crystalline forms in the complex ester mixture seemed very likely.