Potent antiviral potamogetonyde and potamogetonol, new furanoid labdane diterpenes from Potamogeton malaianus

Abstract

New furanoid labdane diterpenes, potamogetonyde (3) and potamogetonol (4), together with two known compounds, potamogetonin (1) and 15,16-epoxy-12-oxo-8(17),13(16),14-labdatrien-20,19-olide (2), were isolated from the CH2Cl2 extract of Potamogeton malaianus. The chemical structures of 1-4 were elucidated by the analyses of their spectral data, mainly by 1D and 2D NMR techniques. Potamogetonyde (3) and potamogetonol (4) exhibited potent antiviral (HSV-1) activity with respective IC50 values of 8 and 3 μg/mL. Compounds 1-4 possessed cytotoxicity toward insect cells (fall armyworm and mosquito larvae, IC50 of 11-72 μg/mL). Furanoid diterpenes 3 and 4 also exhibited cytotoxicity against the Vero cell line with respective IC50's of 31 and 28 μg/mL, while 1 and 2 were inactive at 50 μg/mL. Compounds 1-4 were inactive (at 20 μg/mL) against KB and BC cell lines and showed only weak antimycobacterial activity against Mycobacterium tuberculosis H37Ra with minimum inhibitory concentrations of 50-100 μg/mL.