Antioxidant dehydrotocopherols as a new chemical character of Stemona species
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- 作者：Brem ; Brigitte ; Seger ; Christoph ; Pacher ; Thomas ; Hartl ; Markus ; Hadacek ; Franz ; Hofer ; Otmar ; et. al.
- 关键词：Stemona tuberosa ; Stemona collinsae ; Stemona curtisii ; Stemona cochinchinensis ; Stemona kerrii ; Stemona burkillii ; Stemona pierrei ; Stemonaceae ; Tocopherols ; Dehydrotocopherols ; Antioxidant ; Radical scaveng
- 刊名：Phytochemistry
- 出版年：2004
- 出版时间：October, 2004
- 年：2004
- 卷：65
- 期：19
- 页码：2719-2729
- 全文大小：400 K
文摘
From the roots of various Stemona species four new dehydrotocopherols (chromenols) were isolated and their structures and stereochemistry elucidated by spectroscopic methods. The double bond between C-3 and C-4 proved to be a typical chemical character of the genus found in most of the species. Various C-methylations of the aromatic ring reflect differences in methyltransferase activities and agreed with the current species delimitations showing an exclusive accumulation of dehydro-??-tocopherol for the Stemona tuberosa group, whereas different provenances of Stemona curtisii were characterized by dehydro-??-tocopherol accompanied by small amounts of dehydro-??-tocopherol. From Stemona collinsae all four tocopherols were isolated with a clear preponderance of dehydro-??-tocopherol accompanied by smaller amounts of the rare dehydro-??-tocopherol. Stemona burkillii and a group of unidentified species showed a weak accumulation trend towards dehydro-??-tocopherol, whereas Stemona cochinchinensis and especially Stemona kerrii clearly differed by a preponderance of chromanol derivatives. In Stemona cf. pierrei no tocopherols could be detected at all. Based on TLC tests and microplate assays with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) the antioxidant capacities of all chromenol derivatives were comparable with that of ??-tocopherol showing no significant differences among each other, except for a more rapid kinetic behaviour of the 5,7,8-methylated dehydro-??-tocopherol.