1. A process for the extraction and purification of the diterpene alcohol known as Plaunotol of the formula: ##STR3## wherein dried ground leaves of the Thai medicinal plant, "Plau-noi" Croton sublyratus Kurz are first extracted with an unsubstituted lower aliphatic alcohol, and then the extract is turn extracted with a chlorinated hydrocarbon solvent, the resultant extract is partitioned between an unsubstituted lower aliphatic alcohol and a hydrocarbon solvent, the alcohol is treated with a dilute alkali solution to hydrolyze unwanted compounds, and the Plaunotol is separated from the impurities by extraction with a hydrocarbon solvent.
2. A process as claimed in claim 1 wherein the lower aliphatic alcohol is C1 to C4 monohydric aliphatic alcohol.
3. A process as claimed in claim 2 wherein the lower aliphatic alcohol is methanol or ethanol.
4. A process as claimed in claim 1 wherein the chlorinated hydrocarbon is methylene chloride, chloroform or carbon tetrachloride.
5. A process as claimed in claim 1 wherein the hydrocarbon is n-hexane, cyclohexane or heptane.
6. A process as claimed in claim 1 wherein the alcoholic extraction of the dried ground leaves is carried out at a temperature of from 60° to 80° C. for a period of 60 to 120 minutes in an agitated extracting vessel.
7. A process as claimed in claim 1 wherein the hydrocarbon extract of Plaunotol is filtered through an adsorbent.
8. A process as claimed in claim 7 wherein the adsorbent is kieselguhr, diatomaceous earth, fullers earth or bentonite.
9. A process as claimed in claim 1 wherein the chlorinated hydrocarbon extract is treated with activated carbon prior to hydrolysis.