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Journal of Chemistry, Vol. 41, No. 1, P. 1, 2003 short communication: Further Study on Chemical Constituents of Croton tonkinensis Gagnep., Euphorbiaceae Received 15-2-2003 1 Phan Minh Giang , Jung Joon Lee2, Phan Tong Son1 1 Faculty of Chemistry, Vietnam National University, Hanoi 2 Anticancer Research Laboratory, Korea Research Institute of Bioscience and Biotechnology Croton tonkinensis Gagnep., commonly named in Vietnamese as "Kho sam Bac Bo", is a tropical shrub native to the Northern Vietnam. Its dried leaves (Folium Tonkinensis) have been used in Vietnamese traditional medicine to treat boils, abscesses, impetigo, abdominal pain, dyspepsia, dysentery, gastric and duodenal ulcers [1, 2]. The plant is of our interest since its varied biological activities demonstrated in our various in vitro bioassays including anti-inflammatory, anticancer, antiplasmodial, antibacterial and antifungal. Previously we reported on the isolation and structural determination of a new diterpenoid ent7 -hydroxy-15-oxokaur-16-en-18-yl acetate [3,4] from the ethanol extract of the leaves of C. tonkinensis. Investigation of the methanol extract of the leaves of C. tonkinensis by HPLC coupled with PDA detector revealed the presence of 3 main flavonoids (in total 60.43% of the extract) one of which was isolated and structurally identified as tiliroside on the basis of ESIMS, 1H NMR, 13C NMR spectra [5]. The other constituents of the extract are diterpenoids (12.5%) among which four ent-kaurane-type diterpenoids were isolated and structurally characterized on the basis of ESIMS, FABMS, 1D and 2D NMR including two new ent-1 -acetoxy7 ,14 -dihydroxykaur-16-en-15-one (1.26%) and ent-18-acetoxy-7 ,14 -dihydroxykaur-16en-15-one (1.22%) together with two known ent-7 ,14 -dihydroxykaur-16-en-15-one (0.57%) [6] and ent-7 -hydroxy-15-oxokaur-16-en-18-yl acetate (5.6%). The phytosterols -sitosterol, stigmasterol and two long chain alkyl alcohols were also isolated from the non-polar parts of the methanol extract. Acknowledgements: The authors are grateful to International Foundation for Science (IFS, Stockholm, Sweden) and the National Basic Research Program in Natural Sciences for the financial support for this work. References 1. Vo Van Chi. Dictionary of Vietnamese Medicinal Plants, Medicine Publishing House, HCM City, P. 622 - 623 (1997). 2. Selected Medicinal Plants in Vietnam. Science and Techniques Publishing House, Hanoi, Vol. 1, P. 260 - 262 (1999). 3. Phan Tong Son, Van Ngoc Huong, Phan Minh Giang, Walter C. Taylor. Vietnam J. Chem., Vol. 37, No. 4, P. 1 - 2 (1999). 4. Phan Tong Son, Phan Minh Giang, Walter C. Taylor. Aust. J. Chem., Vol. 53, P. 1003 1005 (2000). 5. K. Y. Jung, S. R. Oh, S. H. Park, I. S. Lee, K. S. Ahn, J. J. Lee, and H. K. Lee. Biol. Pharm. Bull., Vol. 21, P. 1077 - 1078 (1998). 6. N. B. Perry, E. J. Burgess, S. H. Baek, R. T. Weavers, W. Geis, A. B. Mauger. Phytochem., Vol. 50, P. 423 - 433 (1999). 1 2