1133. The pigments of stick lac. Part I. Isolation and preliminary examination

Abstract

Laccaic acid contains a t least four components. Methods have been devised for separating these and for obtaining pure the major component, laccaic acid A,. This compound, of probable molecular coinposition C,,H,,NO,,, is a quinone-carboxylic acid containing four acetylatable hydroxyl groups (three arranged as in purpurin), one C-Me group, and a nonbasic nitrogen atom which can be estimated by the van Slyke method. The chromophore of laccaic acid A, is probably that of an anthraquinone modified by further conjugation.T H E insect Lnccifer Zacca Kerr, found on the twigs of certain trees native to India and South-East Asia, produces a resin known as stick 1ac.l Extraction of stick lac with dilute sodium carbonate solution removes pigments and leaves behind shellac. Treatment of the extract with chalk or alum precipitates lac-dye which, until the advent of synthetic dyes, was of considerable commercial importance. isolated material named laccaic acid. The isolation was effected by leaching the powdered dye with dilute acid. The crude pigment from the acid extract was purified by decomposing its lead salt with hydrogen sulphide and recrystallisation from water. Schmidt made preliminary studies of the chemistry of laccaic acid, but a more detailed investigation was carried out by Dimroth and Gold~chmidt,~ who isolated laccaic acid by extracting powdered stick-lac with water. Concentration of the extract and acidification with hydrochloric acid precipitated crude laccaic acid as a red solid which was recrystallised from formic acid. Chemical studies, summarised by Thorn~on,~ led Dimroth and Goldschmidt to a partial formulation of laccaic acid as a polysubstituted anthraquinone. This was elaborated by Mayer5 to the expression (I). Tschirch and Ludy6 obtained support for the presence of the anthraquinone nucleus from zinc dust distillation studies. Evidence for the presence of nitrogen in laccaic acid was obtained by Kamath and Potnis by analysis of the crude calcium salt of laccaic acid, but the H O 1 ~* ~C O M e nature of their preparation could not generate confidence HO \ Et in the result. Recently Venkataraman and his co-workers OH ,(TI found laccaic to be a mixture of pigments containing l-2yo of nitrogen present as -NH,.8 A second pigment isolated by Tschirch and Ludy6 from stick lac, and called erythrolaccin was recently formulated as 1,3,5,6-tetrahydro~y-8-methylanthraquinone.~ It is the purpose of this Paper to report work carried out on laccaic acid, isolated from stick lac essentially by the method of Dimroth and Gold~chmidt,~ in which the major component of laccaic acid has been obtained pure.Laccaic acid represented about ly0 by weight of stick lac, as was also found by DimrothFrom lac-dye Schmidt

An adsorption and thermodynamic study of lac dyeing on cotton pretreated with chitosan

“…The neutralization of laccaic acid A, in water containing 4% of dimethyl sulfoxide by volume, by 0.1 M sodium hydroxide gave pK a2 and pK a3 values to be about 4.4 and 6.5, respectively, whilst the most strongly acidic group was completely ionized below pH 4.0 [29]. Laccaic acid A, the major lac dye component [30,31], may then bind to the pretreated cotton via hydrogen bonding and ionic interactions under acidic conditions. Chitosan could then act as an organic mordant to enhance the uptake of lac dye on the cellulose surface resulting in lac dye sorption on the cotton.…”

Enhancement of lac dye adsorption on cotton fibres by poly(ethyleneimine)

“…It may also be used for oil painting, in varnishes and possibly in watercolors. It is identified to be two groups of substances: four closely related laccaic acids A, B, C, and E, all of which are water-soluble pigments producing a red color and erythrolaccin which dissolves in alcohol producing pale-yellow color [3][4][5].…”

Identification of anthraquinone coloring matters in natural red dyes by electrospray mass spectrometry coupled to capillary electrophoresis

“…20 The lac is gathered in the hills near the Ganges river (rich in laccaic acids A, D and E) and in Thailand (rich in laccaic acids B and C). 15,16,21 Madder 19 is a dye found in the roots of various plants of the Rubiaceae family: Rubia tinctorum, R. peregrina, R. cordifolia, R. munjista and others. Plants of this family grow in South America and Europe and their active components are mainly anthraquinones-alizarin and purpurin.…”