Two New Coumarins from the Roots and Stems of Nicotiana tabacum and their Bioactivity
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TWO NEW COUMARINS FROM THE ROOTS AND STEMS OF Nicotiana tabacum AND THEIR BIOACTIVITY
Li-Jun Zhu,1,2 Dian Luo,1,2 Na Lv,1 Yin-ke Li,2 Qi-Li Mi,2 Jin Wang,2 Wei-Song Kong,2 Qian Gao,1 Gan-Peng Li,1 Guang-Yu Yang,1,2 Qiu-Fen Hu,2 Ying Guan,1,2* and Yan-Qing Ye1,2*
Two new coumarins, 6-hydroxymethyl-3-prenyl-7-methoxycoumarin (1) and 6-hydroxyethyl-3-prenyl-7methoxycoumarin (2), together with three known coumarins (3–5), were isolated from the roots and stems of Yunyan-300, a variety of Nicotiana tabacum L. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1 and 2 were tested for their anti-methicillinresistant Staphylococcus aureus (anti-MRSA) activity and their antioxidant activity. The results revealed that compounds 1 and 2 showed good anti-MRSA inhibitions with IZD of 12.2 ± 1.8 and 11.8 ± 1.5 mm, respectively, and antioxidant activity with an IC50 value of 4.65 and 4.85 μg/mL, respectively. Keywords: Nicotiana tabacum, coumarins, anti-MRSA activity, antioxidant activity. Nicotiana tabacum (Solanaceae) is an important economic crop because its leaves are used as raw material in the tobacco industry [1, 2]. In addition, people also use the aerial plant as insecticide, sedative, diaphoretic, anesthetic, and emetic agents in Chinese folk medicines [2]. In previous phytochemical investigations, more than 4000 compounds have been identified from N. tabacum [2, 3]. The main constituents were diterpenoids [4, 5], sesquiterpenoids [6–8], flavonoids [9–11], alkaloids [12–14], coumarins [15, 16], and the like. The roots and stems of N. tabacum are the main by-product in tobacco planting, and the multipurpose utilization of the roots and stems of N. tabacum is an interesting topic and attracts more and more attentions [7, 10, 17]. Coumarins, also known as benzopyran-2-ones, are an important kind of secondary metabolites found in many high plants and are probably produced by plants as a chemical defense to discourage predation. There is growing interest in coumarins due to their diversity with respect to structural complexity and because they possess promising therapeutic properties with low toxicity [18, 19]. In order to increase the pharmacodynamic value of N. tabacum, our group has investigated the chemical constituents of the roots and stems of Yunyan-300, a variety of Nicotiana tabacum L. As a result, two new coumarins (1 and 2), together with three known coumarins (3–5), were isolated from this plant. The structures of the isolated components were characterized by comprehensive spectroscopic analyses and by comparison with published data. Compounds 1 and 2 were also tested for their anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) and antioxidant activity. The air-dried and powdered roots and stems of N. tabacum (5.2 kg) were extracted with 70% aqueous acetone (3 × 8 L) at room temperature and filtered to yield a filtrate, which was successively evaporated under reduced pressure to obtain a crude extract (285 g). This crude extract was subje
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