通过分析红树植物秋茄(Kandelia obovata(Sheue,Liu & Yong))幼苗叶片酚类化合物含量和结构动态变化,阐述了其从成熟到衰老过程中酚类化合物的分布特征和规律.结果表明:秋茄叶片从芽至第6对叶,总酚含量((144.73±8.56)mg/g～(38.79±2.14)mg/g)和可溶缩合单宁含量((128.44±12.73)mg/g～(19.87±2.45)mg/g)均呈现先降低后升高的趋势,生理活力强的第3对成熟叶的总酚及可溶缩合单宁含量最低.通过高效液相色谱(HPLC)分析不同发育阶段叶片单宁主要降解产物(翠雀素、花青素、花葵素)的相对含量,逆向推断单宁结构差别:其中花青素含量最多且相对含量稳定; 翠雀素含量从幼嫩组织到成熟叶片逐渐增加,芽和芽中幼叶含量较低; 花葵素含量在芽中较高,其他组织中含量相差不大.由此可知,从芽中幼叶到第6对叶这一发育过程中单宁结构的羟基数量不断增加.通过基质辅助激光解吸附飞行时间质谱(MALDI-TOF MS)对各发育阶段叶片单宁结构进行分析:缩合单宁组分从二聚体到十四聚体广泛分布于芽和叶片,但从第3对叶片开始,单宁聚合体与糖苷结合,特别是在第5,6对已经开始衰老的叶片中这一现象更为明显.本研究结果显示了秋茄叶片不同发育阶段酚类化合物含量和结构的变化,为进一步研究叶片中酚类化合物对于红树植物的生存和适应性提供了理论基础和科学依据.
In this study,we quantified the overall pools of phenolics in the leaves of Kandelia obovata(Sheue,Liu & Yong),and identified the major constituents of these pools and stated their changes during leaf maturation and senescence.The contents of polyphenolics((144.73±8.56)mg/g to(38.79±2.14)mg/g)and soluble condensed tannins((128.44±12.73)mg/g to(19.87±2.45)mg/g)first decreased and then increased from bud to older leaves.The lowest content of polyphenolics and soluble condensed tannins appeared in the third mature leaves,as they showed the strongest physiological activity.Meanwhile,we used HPLC to identify the relative contents of degradation products of tannins(delphinidin,anthocyanin and pelargonidin),thus to distinguish the structure differences of tannins.Among them,the content of anthocyanin was found to be relatively high and constant.The content of delphinidin was lower in bud and young leaves,and increased gradually in older leaves.In contrast,the content of pelargonidin was higher in bud,while no significant difference was observed among other tissues.Hence,it suggested that the hydroxyl number of tannins increased from young to older leaves.Moreover,we used MALDI-TOF MS to analyze the tannins structure among the plant tissues.The results showed that the chemical structure of condensed tannins included 13 types of polymers(from dimer to tetradecamer).Specifically,the tannins polymers were combined with glucoside from the third pair leaves,particularly in the fifth and sixth pair leaves,which were senescent leaves.Our results reveal the changes in relative content and chemical structure of tannins at the different developmental stages of K. obovata,and provide the essential basis for studying the function of tannins to the coastal ecosystem.
