The purpose was to screen antibacterial constituent from the barks of Pterocarya stenoptera

which was a Chinese traditional drug often used to treat bacterial and fungous skin diseases for hundreds of years.Through extraction

precipitation

silica gel column adsorption chromatography

Sephadex LH-20 gel chromatogra-phy using a bioassay-guided fractionation technique（An antibacterial experiment in vitro was used as the screening technique）

a red needlelike liposoluble compound with excellent antibacterial activity to Diplococcus cata

Strepto-coccus albus

Gibberella saubinetii

Salmonella sp.

Bacillus subtilis

and so on

was isolated from the barks of P.stenoptera.The compound was identified as 2-ethoxy-5-hydroxynaphthalene-1

4-dione（C12H10O4

M = 218） by EI-MS

1H-NMR

13C-NMR and DEPT.The structure of another antibacterial compound

juglone（Azadbakht M

2005）

is very similar to 2-ethoxy-5-hydroxynaphthalene-1

4-dione except for a 2-ethoxy

which suggest that this kind of chemical structure may has potential value for development and application of new antibacterial compound.The results in this paper had not only revealed the antibacterial activity substance of of P.stenoptera

but also laid the foundation for the study of quality standard of P.stenoptera and antibacterial active section for externally used.