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TitlePossible protective role for 3',4'-dihydroxyflavones induced by enhanced UV-B in a UV-tolerant rice cultivar
Publication TypeJournal Article
Year of Publication1998
AuthorsMarkham, K.R., Tanner G.J., Caasi-Lit M., Whitecross M.I., Nayudu M., and Mitchell K.A.
Pagination1913 - 1919
Date Published1998
ISSN00319422 (ISSN)
Keywords3',4' dihydroxyflavone, article, flavone derivative, glucoside, high performance liquid chromatography, isoorientin 2'' o beta [6 o 4 coumaroylglucoside], isoorientin 2'' o beta [6 o feruloylglucoside], nonhuman, nuclear magnetic resonance, radiation absorption, radiation protection, rice, ultraviolet b radiation, ultraviolet irradiation, unclassified drug
AbstractThe investigation reported here defines the structures of the flavonoids enhanced by increased UV-B levels in a UV-tolerant rice cultivar, M202 [Caasi-Lit, M., Whitecross, M. I., Nayudu, M., Tanner, G. J., Aust. J. Plant Physiology, 1997, 24, 261], as isoorientin-2-O-β-D-glucopyranoside, isoorientin-2-O-β-[6-O-E-p-coumaroylglucopyranoside] and isoorientin-2-O- β-[6-O-E-feruloylglucopyranoside], the last two being new natural products. Enhanced to a lesser extent were the isovitexin analogues of the last two, together with isoscoparin-2-O-β-[6-O-E-p-coumaroylglucopyranoside]. The UV- susceptible cultivar, Dular, accumulated virtually none of these compounds and no enhancement resulted from increased UV-B levels. Since the two classes of flavonoid differ very little in their ability to absorb radiation in the 290-320 nm range, these findings support recently expressed views that flavonoids may play a more subtle role in plant UV-B protection than simple UV-B screening. The presence of an ortho-dihydroxyl grouping in the structure is seen as of pivotal importance in that role, which may involve free radical scavenging or more efficient dissipation of UV energy.

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