9, 10-Dihydrophenanthrene derivatives from Pholidotayunnanensis and scavenging activity on DPPH free radical

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.

Keywords:

• Pholidota yunnanensis
• Orchidaceae
• Dihydrophenanthrene
• Phoyunnanins A–C
• Free radical scavenging activity

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.