Antioxidant dehydrotocopherols as a new chemical character of Stemona species

• Published in: Phytochemistry (Oxford) Vol. 65; no. 19; pp. 2719 - 2729
• Main Authors: Brem, Brigitte, Seger, Christoph, Pacher, Thomas, Hartl, Markus, Hadacek, Franz, Hofer, Otmar, Vajrodaya, Srunya, Greger, Harald
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 01.10.2004; Elsevier
• Subjects: Antioxidant; antioxidant activity; antioxidants; Antioxidants - chemistry; bioaccumulation; Biochemistry & Molecular Biology; Biological and medical sciences; Chemical constitution; chemical structure; Chemosystematics; Chromatography, High Pressure Liquid; chromenols; Dehydrotocopherols; free radical scavenging activity; Free Radicals - chemistry; Fundamental and applied biological sciences. Psychology; Life Sciences & Biomedicine; Magnetic Resonance Spectroscopy; Molecular Structure; phytochemicals; Plant cytology, morphology, systematics, chorology and evolution; plant extracts; Plant physiology and development; Plant Sciences; Radical scavenger; Science & Technology; spectral analysis; Spermatophyta; Stemona; Stemona burkillii; Stemona cochinchinensis; Stemona collinsae; Stemona curtisii; Stemona kerrii; Stemona pierrei; Stemona tuberosa; Stemonaceae; Stemonaceae - chemistry; Stemonaceae - classification; Systematics (diagnosis, chromosome numbers); tissue distribution; Tocopherols; Tocopherols - chemistry; Indonesia; Stemonaceae; Stemona pierrei; Stemona cochinchinensis; Chemosystematics; Antioxidant; Radical scavenger; Stemona burkillii; Stemona kerrii; Stemona collinsae; Tocopherols; Stemona tuberosa; Dehydrotocopherols; Stemona curtisii; antioxidant; VITAMIN-E; tocopherols; ANTIFUNGAL STILBENOIDS; QUINONES; OILS; radical scavenger; ALPHA-TOCOPHEROL; TOCOPHEROL-CYCLASE; chemosystematics; dehydrotocopherols; ALKALOIDS; Monocotyledones; Molecular structure; α-Tocopherol; Stereochemistry; Slemona pierrei; Angiospermae; Isolation; Spermatophyta; Intraspecific comparison; Tocopherol
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2004.08.023

Four dehydrotocopherols were isolated from the roots of various Stemona species and their structures and stereochemistries elucidated by spectroscopic methods. Various accumulation trends towards α-, β-, γ-, or δ-form were in line with present species delimitations. Antioxidant activities tested with the free radical DPPH on TLC and microplate assays were comparable with that of α-tocopherol 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-δ-tocopherol for the Stemona tuberosa group, whereas different provenances of Stemona curtisii were characterized by dehydro-γ-tocopherol accompanied by small amounts of dehydro-α-tocopherol. From Stemona collinsae all four tocopherols were isolated with a clear preponderance of dehydro-δ-tocopherol accompanied by smaller amounts of the rare dehydro-β-tocopherol. Stemona burkillii and a group of unidentified species showed a weak accumulation trend towards dehydro-α-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 α-tocopherol showing no significant differences among each other, except for a more rapid kinetic behaviour of the 5,7,8-methylated dehydro-α-tocopherol.