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Keywords:
coumarin glucosides; flavonoids; lignans; structure elucidation; Wikstroemia nutans
Abstract
Wikstroemia mutans Champ, ex Benth., a traditional herbal medicine collected at the Lingnan region of China, was chemically investigated. A new biscoumarin glucoside, wikstronutin (1). along with three known bis- and tricoumarin glucosides (2-4). two flavonoid glycosides (5-6). and eleven lignan glucosides (7-17) were isolated from the stems and roots of W. nutans. The new structure including its absolute configuration was elucidated based on a combination of ID and 2D NMR. UV. IR. HRESLMS spectroscopic data, as well as chemical transformation. Compounds 1-17 were first isolated from the plant species W. nutans, while compounds 1-3. 8. and 11 were reported from the genus Wikstroemia for the first time. All co-isolates were evaluated for their in vitro inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide (EPS) in murine RAW264.7 macrophage cells. The antibacterial activity of the selected compounds was also tested. Our work enriches the structure diversity of the secondary metabolites from the genus Wikstroemia.
Introduction
The genus Wikstroemia (Thymelaeaceae) contains approximately 62 species, which are widespread throughout the subtropical regions of Asia and Oceania [1]. Nineteen species of the genus Wikstroemia are found to be domestic in China, such as W. nutans. W. indica, and W. canescens [2]. Previous investigations have not only reported diverse secondary metabolites from the genus, but also promising pharmacological activities of the extracts and chemical constituents produced by Wikstroemia species, including cardiovascular, neuroprotective. hepatoprotective. anti-inflammatory, and antitumor activities [1.3]. The plant species W. nutans is widely distributed in the areas of the Guangdong and Guangxi provinces of China, and the whole plants of this species are used as a folk medicine for the treatment of arthritis, mastitis, and pain relief [2]. Interestingly. the traditional medical usages are highly consistent with the phytologically related medicinal plant species W. indica that has already been approved to use as a prescription drug in China [3]. Owing to the intriguing therapeutic effects associat- ed with W. indica, extensive phytochemical studies on W. indica have been pursed [3.4]. However, there is no report on the phytochemical and pharmacological investigations upon W. nutans.
Coumarins (2H-l-benzopyran-2-one) are a large quantity of phenolic substances found in plants and microorganisms [5]. These naturally occurring coumarins were...