Structure of fructans from excised leaves of New Zealand flax

The accumulation of total water-soluble carbohydrate, and specifically sucr ose and fructan, by excised leaves of Phormium tenax and P. cookianum (fami ly Phormiaceae J. G. Agardh, order Asparagales) was investigated. Total wat er-soluble carbohydrate content of excised leaves of P. tenax and P. cookia num increased during 48 h of continuous illumination at an average rate of 1.3 and 0.9 mg g(-1) fresh weight leaf per hour, respectively. The sucrose content of excised leaves increased throughout the experimental period. The fructan content of excised leaves of P. tenax increased slightly throughou t the experimental period, whilst that of P. cookianum? was variable and sh owed no overall change. Chemical and spectroscopic analysis of the fructans obtained from the two Phormium species showed that they were similar to ea ch other and contained mostly 1-linked and terminal fructofuranosyl (Fruf) residues, together with smaller amounts of 6-linked Fruf, 1,6-branched Fruf , terminal and 6-linked glucopyranosyl residues. Separation of the fructans by thin-layer and high-performance anion-exchange chromatography revealed the presence of a complex mixture of fructo-oligosaccharides and higher mol ecular weight fructan. The branched structure of the fructans isolated from excised leaves of Phormium resembles that of fructans and fructo-oligosacc harides isolated from some related species within the order Asparagales (Ag ave vera cruz, Cordyline australis and Urginea maritima): but is distinct f rom the linear structure of fructans from others (Allium cepa and Asparagus officinalis). The structural heterogeniety of fructans within both the ord er Asparagales and superorder Liliiflorae may be a useful chemotaxonomic ai d. (C) 2001 Elsevier Science Ltd. All rights reserved.