Furan-2-Carboxylic Acids from the Roots of Nicotiana tabacum and their Bioactivities

Two new furan-2-carboxylic acids, 5-(3-hydroxy-5-(hydroxymethyl)-4-methoxyphenyl)-3-methylfuran-2-carboxylic acid (1) and 5-(4-hydroxy-5-methoxy-2-methylphenyl)-3-methylfuran-2-carboxylic acid (2), together with two known furan-2-carboxylic acids (3 and 4) were isolated from the roots of Nicotiana tabacum. Their structures were determined by means of HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1 and 2 were tested for their anti-tobacco mosaic virus (TMV) and cytotoxicity activities. The results revealed that compounds 1 and 2 showed high anti-TMV activity with inhibition rate of 35.8 and 32.6%. These rates are close to that of positive control. Compounds 1 and 2 also showed moderate to weak inhibitory activities against some tested human tumor cell lines with IC50 values in the range of 1.5–6.0 μM.