Possible protective role for 3′,4′-dihydroxyflavones induced by enhanced UV-B in a UV-tolerant rice cultivar

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• 作者：Markham ; Ken R. ; Tanner ; Gregory J. ; Caasi-Lit ; Merdelyn ; Whitecross ; Malcolm I. ; Nayudu ; Murali ; et. al.
• 关键词：Oryza sativa ; Gramineae ; rice ; UV-B ; tolerance ; 3&prime ; 4&prime ; -dihydroxyflavones ; isoorientin-2&Prime ; -O-β ; -[6-O-E-feruloylglucoside] ; isoorientin-2&Prime ; -O-β ; -[6-O-E-p-coumaroylglucoside]
• 刊名：Phytochemistry
• 出版年：1998
• 出版时间：December 5, 1998
• 年：1998
• 卷：49
• 期：7
• 页码：1913-1919
• 全文大小：258 K

文摘

The 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 290–320nm 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.