Saponarin : a new glucoside, coloured blue with iodine / by George Barger.

  • George Barger
Date:
[1906?]
Catalogue details

Licence: Public Domain Mark

Credit: Saponarin : a new glucoside, coloured blue with iodine / by George Barger. Source: Wellcome Collection.

    16/20 page 1223
    or to the corresponding reduced chalkone formula : oh/ oh <!0-(.'H(0H )-C!I(< HI) • UH. OH Both these formulae contain six hydroxyl groups, whereas both Perkin’s determinations and those of the author show that there are but five acetyl groups in acetylvitexin. As the number of hydroxyl groups is unusually large, it may be that one escapes acetylation. Acetylsaponarin contains nine acetyl groups. Assigning to the glucose part of the molecule the structure of an ay-anhydride, this would have four hydroxyl groups; the vitexin part would therefore have five, and, after hydrolysis, six, hydroxyl groups. The formation of |>hydroxyacetophenone from an u/3-hydroxypyrone compound of the type figured would probably take place through the elimination of water, yielding the complex CH2IC(OH),C6H4*OH, the process being analogous to the formation of lsevulic acid from dextrose. Mr. Perkin has, by letter, raised objections to the above constitution for vitexin, and has suggested the presence of a reduced phloroglucinol nucleus, which would lead to a formula of the following type, with five hydroxyl groups : H 0 > H OH H> OH-^ \j\S OH CO CH-OH The study of vitexin is complicated by the difficulty experienced, by Perkin as well as by the author, of preparing crystalline derivatives other than the acetyl compound. Numerous attempts were made to prepare a crystalline azobenzene derivative and an alkyl ether ; in the former case, a resinous product was formed, and in the latter the reaction was very slow and incomplete, whether methyl iodide or dimethyl sulphate were used. Vitexin seems to belong to a new class of colouring matters which are closely allied to the flavone group, and differ from the correspond¬ ing flavone derivatives by two molecules of water. Scoparin, which, according to Perkin, is probably methoxyvitexin, would also belong to this group. Whether saponaretin is a chalkone derivative corresponding to vitexin, or whether it is identical with homovitexin, cannot at present be determined, nor is it known if the glucoside in Vitex littoralis, from which vitexin is formed by hydrolysis, is identical with saponarin.
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