Page:Indian Medicinal Plants (Text Part 1).djvu/413

Rh Part used : — The root-bark.

Uses: — The powdered root-bark is carminative, stomachic, tonic and stimulant ; useful in atonic dyspepsia, debility and slight cases of fever (Moodeen Sheriff).

The powdered bark (mixed with gingelly oil) is also said to be sometimes used in South India as an external application for itch and other skin diseases (Watt).

On treating this dye-stuff with carbon bisulphide five crystalline substances are extracted, together with a wax and a resinous colouring matter.

1. A substance of the formula C16H12O5. This crystallises in long, orange-red needles, melting at 200° ; it sublimes at higher temperatures, partially carbonising. Its alkaline solutions have a purple tint, and the corresponding salt can be obtained in the form of violet-colored needles sparingly soluble in alcohol. There is a great deal of similarity in appearance, properties, and melting point between emodin from Rhamnus frangula and this substance. They are probably identical.

2. A substance of the formula C16H14O4(A). This forms long, colourless needles, which decompose at about 260° before melting ; it is soluble in alkaline solutions with a yellowish brown coloration.

3. A substance of the formula C16H14O4(B). This crystallises in pale yellow needles melting at 173°. With acetic anhydride, it yields what is probably a triacetyl compound melting at 227-229°, the alcoholic solution of which has a strong blue fluorescence. Tt dissolves in alkalis forming yellowish brown solutions which on long exposure to air become red, and on treatment with acid yield a precipitate of emodin methyl ether.

4. A substance of the formula C16H8O8. This is an orange-red, crystalline powder, which, when heated, begins to darken at 260°, and melts and carbonises at 275-280°. It is distinguished from the preceding substances by its sparing solubility in most solvents. Solutions of the alkalis dissolve it with an orange-red coloration, and it yields an acetyl derivative, C16H7O8(C2H3O), which crystallises in yellow needles melting and decomposing at 216-220°.

5. A substance of the formula C17H12O5. This is a chocolate-colored, crystalline powder. When treated with dilute alkali, it dissolves with a yellow coloration, but on exposure to air the solution deposits a blue, amorphous precipitate, and it therefore appears to contain in its molecule a reduced quinone group.

6. The wax (C9H16O)n, consists of nearly colourless, minute needles, melting at 72°.