Antitumor activity of acylated oridonin.

14-O-Acyl derivatives of oridonin were prepared and tested for antitumor activity against Ehrlich ascites carcinoma cells in the mouse. In a series of derivatives 7-12, the activity increased with increase of the acyl carbon chain length. The 14-O-benzoyl derivative 5 was shown to have the same order of activity as oridonin. 6-O-Acyl derivatives were also prepared and tested. In a series of derivatives 13-15, no activity was observed at the doses of 5 mg/kg and 10 mg/kg in mice, at which doses oridonin did exhibit activity. Thus, the importance of the ester side chain and the hydrogen-bonding for antitumor activity was demonstrated in oridonin and its derivatives.