Two New Isobenzofurans from the Roots of Yunnan Local Sun Cured Tobacco and Their Bioactivities

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TWO NEW ISOBENZOFURANS FROM THE ROOTS OF YUNNAN LOCAL SUN CURED TOBACCO AND THEIR BIOACTIVITIES

Li-Jia Huang,1,2 Xue Wang,1,2 Meng-Jie Liang,1,2 Yin-Ke Li,2 Wei-Shong Kong,2 Xin Liu,2 Hai-Ying Xiang,2 Qian Gao,2 Qi-Li Mi,2 Liang Deng,2 Guang-Yu Yang,1,3 Ya-Dong Guo,1* and Jing Li1,2*

Two new isobenzofurans, 5-(methoxymethyl)-2,2-dimethyl-2H-furo[3,4-h]chromen-7(9H)-one (1) and 5-(2-methoxyethyl)-2,2-dimethyl-2H-furo[3,4-h]chromen-7(9H)-one (2), together with two known isobenzofurans (3 and 4), were isolated from the roots of Yunnan local sun cured tobacco. Their structures were determined by means of HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1–4 were tested for their anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity. The results revealed that compound 4 showed strong inhibition with IZD of 16.5 ± 2.2. Compounds 1–3 also showed good inhibition with IZD of 13.6 ± 2.0, 14.0 ± 2.3, and 11.8 ± 1.6 mm, respectively. Compounds 1–4 were also tested for their antioxidant activity, and they showed good antioxidant activity with IC50 value of 4.38, 4.57, 4.46, and 4.28 μg/mL, respectively. Keywords: sun cured tobacco, isobenzofurans, anti-MRSA activity, antioxidant activity. Nicotiana tabacum, tobacco, is a stout herbaceous plant belonging to Solanaceae (nightshade family). This plant originated from the tropical Americas (South America, Mexico, and the West Indies) and is now cultivated worldwide because its leaves are used as raw material in the tobacco industry [1, 2]. In addition to smoking or chewing, people also used its aerial plant as insecticide, sedative, diaphoretic, anesthetic, and emetic agents in Chinese folk medicines [2, 3]. Nicotiana tabacum is also a kind of plant containing very complex secondary metabolites in nature. It was reported that more than 2549 kinds of chemical compositions have been identified in N. tabacum, while up to 8700 kinds of chemical compositions were found in tobacco, tobacco substitutes, and cigarette smoke (including combustion products) [4]. Our previous phytochemical investigations have demonstrated that this plant contains sesquiterpenoids [5, 6], flavonoids [7, 8], alkaloids [9, 10], coumarins [11, 12], isobenzofurans [13, 14], and the like. Isobenzofurans belong to a class of heterocyclic compounds, which consists of a benzene ring fused to the 3,4-positions of the furan ring. Among the heterocyclic compounds, isobenzofuran derivatives have emerged as a potent source in the area of drug discovery, and they possess a wide spectrum of biological activities [15, 16]. In the present study, the phytochemicals from the roots of Yunnan local sun cured tobacco (Leye tobacco, a variety of N. tabacum widely cultivated in Huize Prefecture, Yunnan Province) were investigated, which resulted in the isolation of two new (1 and 2) and two known (3 and 4) isobenzofurans. Compounds 1–4 were also tested for their anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) and antioxidant activity. 1) School of Pharmaceutical Science & Yunnan Key

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