Objective: To study the secondary metabolites of an endophytic fungus Alterraria sp. isolated from Saussurea medusa. Method: Alterraria sp. was isolated from the medical plant S. medusa.The strain was cultured in a large-scale after the culture conditions had been optimized. The secondary metabolites were isolated by chromatography methods such as silica gel

Sephadex LH-20 columns

ODS flash column and HPLC

and the analysis of LC-MS. The structures of these compounds were identified by theirphysico-chemical constants and the NMR and MS data. Result: Nine compounds were isolated and identified as spirotryprostatin A (1)

4-hydroxybenzoic aldehyde(2)

4-hydroxyphenyl-2'-hydroxypropanoate (3)

dihydro-p-methoxycinnamic acid(4)

4-methoxybenzoic acid(5)

p-hydroxymethylphenylacetate(6)

4-hydroxyphenyl ethanol(7)

4-hydroxybenzoic acid (8)

3-phenylpropanoic acid(9). All compounds were tested for their inhibitory activities against human lung adenocarcinoma strain A-549.Compound 1 exhibited strong cytotoxic activity against A549 with IC50 value of 2.0 mg·L-1. Conclusion: All the compounds were isolated from Alterraria for the first time.