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Loline alkaloid
A loline alkaloid is a member of the 1-aminopyrrolizidines (often referred to as lolines), which are bioactive natural products with several distinct biological and chemical features. The lolines are insecticidal and insect-deterrent compounds that are produced in grasses infected by endophytic fungal symbionts of the genus ''Epichloë'' (anamorphic species: ''Neotyphodium''). Lolines increase resistance of endophyte-infected grasses to insect herbivores, and may also protect the infected plants from environmental stresses such as drought and spatial competition. They are alkaloids, organic compounds containing basic nitrogen atoms. The basic chemical structure of the lolines comprises a saturated pyrrolizidine ring, a primary amine at the C-1 carbon, and an internal ether bridge—a hallmark feature of the lolines, which is uncommon in organic compounds—joining two distant ring (C-2 and C-7) carbons (see Fig. 1). Different substituents at the C-1 amine, such as methyl, formyl, and acetyl groups, yield loline species that have variable bioactivity against insects. Besides endophyte–grass symbiota, loline alkaloids have also been identified in some other plant species; namely, ''Adenocarpus'' species (family Fabaceae) and ''Argyreia mollis'' (family Convolvulaceae).
==Discovery==
A member of the loline alkaloids was first isolated from the grass ''Lolium temulentum'' and its elemental composition determined in 1892. It was initially named ''temuline'' and later renamed ''norloline''. (Reviewed by Schardl et al. (2007).) Studies in the 1950s and 1960s by Russian researchers established the name ''loline'' and identified the characteristic 2,7 ether bridge in its molecular structure.〔 Since then the analytical methods for purification and analysis of the lolines have been refined and several different loline species have been identified in many ''Lolium'' and related grasses infected by the ''Epichloë/Neotyphodium'' (epichloae) endophytes. Lolines are absent in grass plants that do not harbor the epichloae endophytes, and not all epichloae produce the lolines.〔 Because of the very intimate association of plant and endophyte and difficulties to reproduce the symbiotic conditions ''in vitro'', it was long unknown if the fungus was the producer of the lolines, or if they were synthesized by the plant in response to endophyte infection. In 2001, it was demonstrated that the endophyte ''Neotyphodium uncinatum'' produces lolines in some chemically defined growth media, which suggests that the endophyte is also the producer of the lolines in the grass plant. The lolines have also been reported from some plants in several plant families, suggesting a more widespread occurrence of these compounds in nature.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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