A New Quinazolinone Alkaloid along with Known Compounds with Seed-Germination-Promoting Activity from Rhodiola tibetica Endophytic Fungus Penicillium sp. HJT-A-6.

A new quinazolinone alkaloid named peniquinazolinone A ( 1 ), as well as eleven known compounds, 2-(2-hydroxy-3-phenylpropionamido)- N -methylbenzamide ( 2 ), viridicatin ( 3 ), viridicatol ( 4 ), (±)-cyclopeptin ( 5a / 5b ), dehydrocyclopeptin ( 6 ), cyclopenin ( 7 ), cyclopenol ( 8 ), methyl-indole-3-carboxylate ( 9 ), 2,5-dihydroxyphenyl acetate ( 10 ), methyl m -hydroxyphenylacetate ( 11 ), and conidiogenone B ( 12 ), were isolated from the endophytic Penicillium sp. HJT-A-6. The chemical structures of all the compounds were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR and HRESIMS. The absolute configuration at C-13 of peniquinazolinone A ( 1 ) was established by applying the modified Mosher's method. Compounds 2 , 3 , and 7 exhibited an optimal promoting effect on the seed germination of Rhodiola tibetica at a concentration of 0.01 mg/mL, while the optimal concentration for compounds 4 and 9 to promote Rhodiola tibetica seed germination was 0.001 mg/mL. Compound 12 showed optimal seed-germination-promoting activity at a concentration of 0.1 mg/mL. Compared with the positive drug 6-benzyladenine (6-BA), compounds 2 , 3 , 4 , 7 , 9 , and 12 could extend the seed germination period of Rhodiola tibetica up to the 11th day.