Abstract
Three new 9,10-dihydrophenanthrene derivatives named phoyunnanins A–C, together with six known 9,10-dihydrophenanthrene constituents, 4,4′,7,7′-tetrahydroxy-2,2′-dimethoxy-9,9′,10,10′-tetrahydro-1,1′-biphenanthrene (4), lusianthridin (5), eulophiol (6), 2,4,7-trihydroxy-9,10-dihydrophenanthrene (7) and imbricatin (8), were isolated from the 60% ethanolic extract of air-dried whole plant of Pholidota yunnanensis Rolfe. The structures of phoyunnanins A–C were established as 6-[2′-(3′,3″-dihydroxy-5′-methoxybibenzy)]-4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (1), 6-[6′-(trans-3′,3″-dihydroxy-5′-methoxystilbeny)]-4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (2) and 4,4′,7,7′-tetrahydroxy-2,2′-dimethoxy-9,9′,10,10′-tetrahydro-1,6′-biphenanthrene (3), respectively, on the basis of the spectroscopic analysis. All eight compounds (1–8) were found to show the DPPH free radical scavenging activity with EC50 from 8.8 to 55.9 μM.
Acknowledgements
The authors thank Professor Luoshan Xu, China Pharmaceutical University, for the identification of the plant of Pholidota yunnanesis Rolfe; Professor Yang Ye, Shanghai Institute of Materia Medica of Chinese Academy of Science, for HREI-MS experiments. Thanks are also extended to Xue Zhang and Sanlin Jin for NMR experiments, and Hao Gao and Xinluan Wang for ESI-MS experiments in the Shenzhen Research Centre of Traditional Chinese Medicines and Natural Products.