Methods for purifying camptothecin compounds

A method of purifying 20(S)-camptothecin comprising the steps:

• (1) combining an aqueous base containing an hydroxide ion, a water immiscible organic solvent, and a starting natural plant material containing 20(S)-camptothecin to form a mixture having an aqueous phase containing 20(S)-camptothecin and an organic phase, wherein the lactone ring in said 20(S)-camptothecin is converted to a carboxylate salt in the aqueous phase;
• (2) separating said organic phase from said aqueous phase containing 20(S)-camptothecin;
• (3) acidifying said aqueous phase containing 20(S)-camptothecin to form 20(S)-camptothecin crystals by the addition of an acid whereby the carboxylate salt is reconverted to said lactone ring;
• and
• (4) separating 20(S)-camptothecin crystals obtained in step (3).