Abstract: 19 Compounds were isolated from liquid fermentation of Streptomyces AE21985 with ordinary silica gel chromatography,gel column chromatography and preparative HPLC.With the spectroscopic methods,they were identified as eleven cyclic dipeptide compounds:3-(4-hydroxybenzyl)-6-(1H-indol-3-ylmethyl) piperazine-2,5-dione (1),(3S,6S)-3-((R)-sec-butyl)-6-methylpiperazine-2,5-dione (2),(3S)-3-benzylpiperazine-2,5-dione (3),(3S,6S)-3-(2-methylpropyl)-6-(propan-2-yl)piperazine-2,5-dione (4),3-Isobutylhexahydropyrrolo-［1,2-a］pyrazine-1,4-dione (5),(3S,6S)-3-((R)-sec-butyl)-6-methylpiperazine-2,5-dione (6),(3S,6S)-3-isopropyl-6-methylpiperazine-2,5-dione (7),(3S,7R,9S)-7-hydroxy-3-isobutylhexahydropyrrolo［1,2-a］pyrazine-1,4-dione (8),3-(1H-indol-3-ylmethyl)-6-(propan-2-yl)piperazine-2,5-dione (9),(3S,8aS)-3-(propan-2-yl) hexahydropyrrolo［1,2-a］pyrazine-1,4-dione (10) and (3S,6S)-3-benyl-6-methylpiperazine2,5-dione (11);five lactam compounds:(2E)-3-phenylprop-2-enamide (12),3-phenylpropanamide (13),2-phenylacetamide (14),benzamide (15) and 3-(1H-indol-3-yl)propanamide (16);an alkaloid compound:1-H-indole-5-carbaldehyde (17) and two nucleoside compounds:uridine (18) and thymine (19).All the compounds were discovered from this strain for the first time.

Key words: Streptomyces, TLC screening, isolation, structural elucidation