Guangyong Yang, Xia Jianjun, Chunbo Liu
2016
Citations
0
Influential Citations
3
Citations
Journal
Heterocycles
Abstract
Three new furan-2-carboxylic acids, 5-(4-hydroxy-2-methoxy-6-methylphenyl)-3-methylfuran-2-carboxylic acid (1), methyl 5-(4-hydroxy-2-methoxy-6methylphenyl)-3-methylfuran-2-carboxylate (2), and 5-(3-hydroxy-4-methoxy-5methylphenyl)-3-methylfuran-2-carboxylic acid (3), together with two known furan-2-carboxylic acids (4 and 5) were isolated from the leaves of Nicotiana tabacum. Their structures were determined by means of HRESIMS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1-5 were tested for their anti-TMV activities. The results showed that compounds 3 and 4 exhibited high anti-TMV activities with inhibition rates of 29.8 and 30.3%. These rates are close to that of positive control. The other compounds also showed potential activities with inhibition rates in the range of 22.8%~25.4%, respectively. Nicotiana tabacum, tobacco is an important economic crop originating from South America. Its leaves are used as a raw material for the tobacco industry, aerial plant as an insecticide, and also as anesthetic, diaphoretic, sedative, and emetic agents in Chinese folklore medicine. In previous literatures, many new bioactive compounds, such as, sesquiterpenes, alkaloids, lignans, flavonoids, phenylpropanoids, chromanones, biphenyls, phenolic amides, isocoumarins, were isolated from Nicotiana tabacum. In our continuing endeavor to discover new bioactive natural products, an investigation of the leaves of Yunyan 85 (a variety of N. tabacum widely cultivited in China) was undertaken. In continuing efforts to utilize N. tabacum and identify bioactive natural products, the phytochemistry investigation of the leaves of Yunyan 85 (a variety of N. tabacum) led to the isolation of three new (1-3) and two known (4 and 5) furan-2-carboxylic acids. This paper deals with the isolation, structural elucidation, and their anti-TMV activities of these compounds. A 95% aq. MeOH extract prepared from the leaves of tobacco was subjected repeatedly to column chromatography on silica gel and preparative HPLC to afford three new furan-2-carboxylic acids, 5-(4-hydroxy-2-methoxy-6-methylphenyl)-3-methylfuran-2-carboxylic acid (1), methyl 5-(4-hydroxy-2methoxy-6-methylphenyl)-3-methylfuran-2-carboxylate (2), and 5-(3-hydroxy-4-methoxy-5-methylphenyl)-3-methylfuran-2-carboxylic acid (3), together with two known furan-2-carboxylic acids (4 and 5). The structures of the compounds 1-5 were as shown in Figure 1, and the H and C NMR data of 1-3 were listed in Table 1. The known compounds, compared with literature, were identified as 5-(2'-hydroxy-6'-methylphenyl)-3-methylfuran-2-carboxylic acid (4), and 5-((6'-methyl-4'-oxo-3',4'dihydro-2H-pyran-2'-yl)methyl)-3-methylfuran-2-carboxylic acid (5). Compound 1 was obtained as a pale yellow gum, and its (+)HRESIMS gave a quasimolecular ion at m/z 285.0731 [M+Na]. These datas, coupled with C NMR spectroscopic data, established the molecular formula of 1 as C14H14O5. The IR spectrum of 1 exhibited absorption bands for –CO2H (br. 3020 cm), -CO2 (1692 cm ) and aromatic functionality (1610, 1584 cm). The H NMR spectrum of 1 (Table 1) exhibited signals attributable to one methoxy group (δH 3.81 s), one –CO2H (δH 10.04) groups, three olefinic methines (δH 6.19 s, 6.40 s, and 6.29 s), two methyl (δH 1.87 s and 2.40 s) groups, and one phenolic hydroxy group (δH 10.60 s). The C NMR spectrum (DEPT) indicated the presence of an ester or carboxyl carbon (δC 166.9 s), two methyl (δC 8.7 q and 20.1 q), one methoxy group (δC 55.8 q), three Figure 2. Key HMBC ( ) correlations of 1 O HO OH