3. Guaiac
Synonyms Guaiacum resin; Gum guaiac; Resin guaiac.
Biological Source Guaiac is obtained from the heartwood of Guaiacum officinale L. or G. sanctum L., belonging to family: Zygophyllaceae.
Preparation The resin is obtained by cutting the tree and the log is suspended horizontally. The either ends of the log are set on fire and the resin which oozes out is collected carefully in earthen or metallic cups and allowed to harden in shade.
Characteristic Features The guaiac resin is brown or greenish-brown irregular lumps. It has an aromatic odour. The fracture is brittle and splintery and the exposed surface is usually glossy. It melts at 85-90°C. It is insoluble in water, but freely soluble in ethanol, ether, chloroform, creosote, solution of chloral hydrate and alkalies. It is, however, slightly soluble in carbon disulphide and benzene.
It is found to be incompatible in liquid preparations containing acacia, mineral acids, ferric chloride, gold chloride, water, spirit nitrous ether and permanganates.
Chemical Constituents A few of the major resinous constituents belong to the group of ‘lignans’.
These are essentially phenolic compounds with a C18 structure and made up from two C6-C3units.
About 10% of the guaiac is guaiaretic acid which is nothing but diaryl butane. It also contains both α-and β-guaiaconic acids (70%) and guaiacie acid. Besides, it contains traces of vanillin, saponin and volatile oil.
Chemical Tests When a small quantity of the resin is oxidised it gives rise to a distinct blue colouration (guaiac blue) due to the oxidation of α-guaiacic acid.
Uses
1. It is mostly employed as a diaphoretic and an expectorant.
2. It is used as a clinical reagent for the testing of blood and haemoglobin.
3. An ethanolic solution of guaiac is used for the detection of oxidase enzymes and cyanogenetic glycosides.
