Bioactive Terphenyls Isolated from the Antarctic Lichen Stereocaulon alpinum .

Three p -terphenyls ( 2 - 4 )-2-hydroxy-3,5-dimethoxy- p -terphenyl ( 2 ), 2-hydroxy-3,6-dimethoxy- p -terphenyl ( 3 ), and 2,3,5,6-tetramethoxy- p -terphenyl ( 4 )-were isolated for the first time as natural products along with seven known compounds ( 1 , 5 - 10 ) from the Antarctic lichen Stereocaulon alpinum. Structures of the new compounds were elucidated by comprehensive analyses of 1D and 2D NMR and HREIMS experiments. Compound 3 exhibited cytotoxicity against HCT116 cells with the IC 50 value of 3.76 ± 0.03 μM and also inhibited NO production in LPS-induced RAW264.7 macrophages with the IC 50 value of 22.82 ± 0.015 μM.