Two new dihydroamentoflavone glycosides from Cycas revoluta

Abstract

Phytochemical investigation of the ethyl acetate extract of Cycas revoluta Thunb. leaflets afforded five compounds including two new dihydroamentoflavone glucosides, (2S)-I-(2,3)-dihydro-I-7-O-β-d-glucopyranosylamentoflavone (1) and (2S)-I-(2,3)-dihydro-I-7,II-7-di-O-β-d-glucopyranosylamentoflavone (2), in addition to the known compounds prunin (3), vitexin-2″-rhamnoside (4) and protocatechuic acid (5). Compounds (3) and (4) being reported for the first time in this plant. The structures of these compounds were established by the detailed analysis of their spectroscopic data, mainly 1D NMR, 2D NMR, CD and HR-MSD-TOF. The ethyl acetate extract showed weak cytotoxicity against HepG2 (IC₅₀ = 207.6 μg/mL) and RAW 264.2 cells (IC₅₀ = 160.8 μg/mL). Compound 4 showed significant activity towards Leishmania donavani (IC₅₀ = 13.8 μM, IC₉₀ = 34.6 μM). The isolated compounds showed weak antimicrobial activity (IC₅₀>10 μg/mL).

Keywords::

• Cycadaceae
• Cycas revoluta
• amentoflavone glycosides
• antimicrobial
• antileishmanial
• cytotoxicity

Acknowledgements

A. Moawad would like to thank the Egyptian government for a fellowship through the Ministry of Higher Education and Scientific Research, Bharathi Avula, Frank Wiggers and Jannie Marais for recording the MS, CD and NMR data and Marsha Wright for the antimicrobial screening which is supported by the NIH, NIAID, Division of AIDS, Grant No. AI 27094 and the USDA Agricultural Research Service Specific Cooperative Agreement No. 58-6408-2-0009.