634. Trigallic acid, a probable component of tannic acid

King, Harley; White, T.

doi:10.1039/jr9610003231

Cited by 5 publications

(2 citation statements)

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“…It has been established that the pentagalloylglucose represents the core of natural gallotannins, to which three to five additional galloyl groups may be attached by depsidic linkages (2,(8)(9)(10)(11). By chemical analysis, the tannic acid used in our preceding paper (21), like the Aleppo gallotannin, has as major components penta-and hexagalloylg l u c o s e s / T h e synthetic pentagalloylglucose used in the experiments now reported has been shown to be identical with that isolated from gailotannins (6,8,11,13). Since we have obtained similar effects in both cases, we can ascribe the mordanting activity of the natural products to their galloylglucoses and thereby eliminate the involvement of unidentified impurities.…”

Section: A Mordanting With Synthetic P Entamonogallo Y Lglucosementioning

confidence: 86%

“…13), whereas prolonged hydrolysis destroys digallic and trigallic acids, the sole ultimate product being gallic acid. Analytical, chromatographic, and optical identity has been reported between synthetic and naturally occurring gallic acid, digallic acid, and trigallic acid (3,6,11,13,15). There is no clear evidence on the extent to which, in solution or in contact with certain tissue components, the galloylglucoses yield gallic, digallic, or trigallic acids.…”

Section: B Mordanting With Gallic Acidmentioning

confidence: 99%

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Galloylglucoses of low molecular weight as mordant in electron microscopy. II. The moiety and functional groups possibly involved in the mordanting effect.

Simiónescu¹,

Simionescu²

1976

The Journal of Cell Biology

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Synthetic pentamonogalloylglucose applied to fixed tissues acts as a mordant, inducing high and diversified contrast similar to that obtained with natural gallotannins of low molecular weight (LMGG). By the separate use of each of the two moieties of the galloylglucose molecule, it was found that gallic acid is the mordanting agent. Glucose may contribute, however, to the effect by increasing the solubility and cross-linking potential of the compound, since the mordanting induced by gallic acid alone is weaker than that produced by its hexose esters. As suggested by results obtained with various phenolics and benzoic acid derivatives, the functional groups required for the mordanting effect of such agents are the carboxyl group, and at least one hydroxyl group concomitantly present on the benzene ring. In the case of galloylglucoses, it is assumed that the effect is due to hydrolysis products (gallic, digallic, or trigallic acids) or to the multiple hydroxyl groups of the intact molecule. Esters of gallic acid (propyl-and methylgallate), as well as pyrogallol, produce a "reversed staining" of all membranes, except for those of communicating (gap) junctions.In the previous paper (21), we showed that natural gallotannins of low molecular weight (LMGG) commercially available as tannic acid AR, usually extracted from Turkish nutgalls, can be used for increasing and diversifying contrast in electron microscopy, The effect was obtained on tissues previously fixed in one step by Os04 or in two steps by aldehydes and Os04. We demonstrated that the gallotannins act as mordants and ascribed this effect to their major components, namely, the penta-and hexagalloylglucoses, the relative low molecular weight of which may explain their satisfactory penetration into the cells.To exclude the possibility that other minor components or contaminants occurring in these natural gallotannins might be responsible for the mordanting effect, we have carried out experiments with synthetic pentagalloylglucose (i.e. synthetic ester of gallic acid with glucose [5,6] which has been found to be chemically identical to one of the main components of natural gallotannins [1,6,15, 181).In additional experiments we tried to find out which part of the galloylglucose molecule accounts for the mordanting effect and which functional groups are involved in this process. 622

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