Lichen substances water solubility

Many natural substances are acid-base indicators. The most familiar one is litmus, an organic dye extracted from certain lichens. Litmus turns from blue to red in acidic solutions (< pH 7) and from red to blue in basic solutions ( pH 7). Some other natnral indicators include red cabbage extract, blueberry juice, black tea, beet juice, rhubarb, and tomato leaves, and flowers such as the rose, daylily, blue iris, and purple dahlia. Red cabbage extract undergoes sharp changes of color at several pH values. The deep purple color of red cabbage leaves is caused by a mixture of water-soluble... 

Sometimes it is possible to separate a mixture of lichen substances by their different solubility. Usnic acid and atranorin are very soluble in chloroform, but nearly insoluble in methanol. Suitable solvents for recrystallization are n-hexane, benzene, diethyl ether, acetone, ethyl acetate, methanol, ethanol, acetic acid, dioxane or water often mixtures of these solvents are used. Sugar and low molecular carbohydrates are well known for their poor tendency to crystallize. Very important is the use of diethyl ether and dioxane free from peroxides, which are highly explosive. A simple reaction to test these solvents for peroxides is to shake about 3 ml of... 

In spite of the differences in structural formulae, lichen substances have a considerable number of properties in common. All lichen substances proper are crystalline and in most cases acid in character (which accounts for the widely used designation lichen acids), and even in the form of alkaline salts their solubility in water is very poor. Several lichen substances are optically active—this applies to all aliphatics usnic acid even has an unusually high specific rotation. The color of the crystals varies from colorless to white and reddish yellow. Several lichen substances have a very bitter taste. 

Inulin, (CeHioOs) , is a starch-like substance which occurs in the roots of the dandelion and chicory, in the tubers of the potato and dahlia, in certain lichens, and in other vegetable substances. Inulin is a white powder, composed of minute spheres it is slightly soluble in cold water, and very soluble in hot water. An aqueous solution of inulin does not form a jelly, is not colored by iodine, is not fermentable, and is not affected by diastase. It is levorotatory, [o ]d = —36.6°. 

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