Abstract
AbstractRheum tanguticum is a traditional Chinese herbal medicine, which contains abundant anthraquinones. In this study, anthraquinones were efficiently extracted from Rheum tanguticum by subcritical water extraction (SWE). The parameters of extraction time (33–67 min), temperature (100–200°C), and SW flow rate (1.4–4.6 mL/min) were optimized so as to achieve a high yield of the target product. A high yield of the total anthraquinones was achieved under the optimized SWE conditions of extraction time 54 min, extraction temperature 170°C, and the flow rate 2.0 mL/min. The comparison between the SWE and traditional extraction techniques implied that the SWE is an efficient and green alternative method for the extraction of anthraquinones. Four anthraquinone glycosides were purified from the SWE extract by high-speed counter-current chromatography and identified as emodin-1-O-β-D-glucoside, physcion-8-O-β-D-glucopyranoside, chrysophanol-1-O-β-D-glucoside, and chrysophanol-8-O-β-D-glucoside.
Highlights
Rheum tanguticum is widely used for its curative effects against bacterial dysentery, gastric problems, and renal disorders; the herb cools and detoxifies the body and promotes blood circulation [1]
Anthraquinones were obtained by solvent extraction methods such as reflux extraction (RE), ultrasound-assisted extraction (UAE), and microwaveassisted extraction (MAE) [9,10,11,12], and disadvantages such as usage of poisonous solvents, low recovery, and large time consumption were accompanied
Four highly pure anthraquinone glycosides were isolated on a large-scale basis using High-speed counter-current chromatography (HSCCC)
Summary
Rheum tanguticum (family: Polygonaceae) is widely used for its curative effects against bacterial dysentery, gastric problems, and renal disorders; the herb cools and detoxifies the body and promotes blood circulation [1]. The SWE can be directly used in the preparation of food or pharmaceutical products [15] Separation is another important step in the isolation process of the natural products from the herbal medicine [17]. The anthraquinones are obtained from the genus Rheum mainly using column chromatography with gradient elution [18,19]. This separation technique is associated with the following drawbacks: low yield, long operational time, and usage of toxic solvents. High-speed counter-current chromatography (HSCCC) offers high recovery of target components and is widely used for the separation and purification of the natural products [20]. A combination of SWE and HSCCC offers “green extraction” and effective separation of anthraquinones from R. tanguticum. Four highly pure anthraquinone glycosides were isolated on a large-scale basis using HSCCC
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