How to Extract Rutin from Sophora Japonica?

Rutin is also known as vitamin P, ルチン, rutoside, rutine, and ruton, and was first isolated from the plant Rhamnus in 1842 [1].Its chemical formula is C₂₇H₃₀O₁₆·3H₂O, with a relative molecular mass of 610.51. It appears as a pale yellow powder or very fine pale yellow needle-like crystals, odorless, and is prone to degradation when exposed to light, requiring storage in the shade. Its melting point is 177–178 °C. It is easily soluble in methanol, alkaline solutions, and pyridine, slightly soluble in water, soluble in hot water and ethanol, and insoluble in cold water, ethyl acetate, and acetone. It is also insoluble in benzene, ether, and petroleum ether.

Rutin not only prevents capillary fragility and cardiovascular diseases but also has antioxidant, anti-allergic, anti-tumor, antiviral, antispasmodic, cough-suppressing, analgesic, lipid-lowering, blood sugar-lowering, anti-acute pancreatitis, and vasodilatory effects [2-5]. Sophora japonica flowers are the dried flowers and buds of the Sophora japonica L. plant, with the dried flowers referred to as Sophora japonica flowers and the buds as Sophora japonica seeds [6].Hawthorn berries have a cold nature, a bitter taste, and are associated with the liver and large intestine meridians. They possess hemostatic, hypoglycemic, hypotensive, antibacterial, and immune-enhancing effects [7-9], making them the primary raw material for rutin extraction in China.

This paper summarizes and compares recent methods for extracting rutin from Sophora japonica seeds, aiming to provide some reference for improving rutin extraction processes.

1 Decoction Method

The principle of this method is that rutin can be dissolved in a strong alkaline solution and precipitated as crystals under acidic conditions. Li Yingchi et al. [10] used coarse Sophora japonica seed powder as raw material, saturated lime water as the extraction solvent, and 0.5% sodium sulfite solution for crystallization.Liao Huawei et al. [11] found that the number of extraction cycles and extraction time significantly affect the extraction efficiency of rutin in the decoction method. Using fine powder of Sophora japonica as raw material, with a solvent volume of 2,500 mL, extraction time of 40 minutes, and three extraction cycles, they determined the optimal extraction conditions for rutin from Sophora japonica.

2 Percolation method

The percolation method involves placing ground Sophora japonica seeds in a percolation cylinder, continuously adding solvent from the top, and allowing the solvent to flow downward through the Sophora japonica layer to extract rutin. Li Ying-chi et al. [10] used a borax water solution and saturated lime water for percolation.Liu Jinyue et al. [12] used a saturated lime water solution mixed with sodium hydroxide solution as the extraction solvent, and by selecting appropriate concentrations, dosages, and pH values, they achieved a rutin extraction yield of 23%, with the crude rutin product having a purity of 93%.The advantage of the leaching method is its simplicity, making it suitable for large-scale production.

3  Extraction method (alkali extraction followed by acid precipitation)

This method is influenced by factors such as the pH of the extraction alkali solution, solid-liquid ratio, extraction time, and temperature. Shu Xiaohong et al. [13] and Yang Xinhai et al. [14] used the alkali extraction followed by acid precipitation method to extract rutin from Sophora japonica seeds,with the optimal process being the use of a 3% borax solution as the extractant, a solid-liquid ratio of 1:12, followed by adjustment of the pH to 9 using saturated calcium hydroxide, extraction at 95–100°C for 30 minutes, repeating the extraction once using the same method, and adjusting the pH to 3 with hydrochloric acid before allowing the solution to settle.

Tong Jing [15] et al. compared three methods for extracting rutin from Sophora japonica seeds: hot water extraction, ethanol maceration, and alkali extraction followed by acid precipitation. They found that the alkali extraction followed by acid precipitation method yielded the highest purity of rutin, reaching 98.1%.The optimal operating conditions were as follows: use coarse Sophora japonica powder as raw material, add 8 times the volume of solvent, adjust the pH to 9 using boric acid buffer solution and saturated lime water, then use 1% sodium sulfite as an antioxidant, operate for 30 minutes,repeating the process three times, and adjusting the pH to 4with hydrochloric acid. The alkali extraction and acid precipitation method is easy to operate, causes minimal environmental pollution, and has relatively low costs, making it suitable for large-scale industrial production.

4   Reflux extraction method

This method uses ethanol as the extractant and employs a water bath reflux method. Zhang Laixin [16] used three different methods—boiling water extraction, alkali extraction followed by acid precipitation, and ethanol reflux extraction—to extract rutin from Sophora japonica seeds.The results showed that the ethanol reflux extraction method yielded the highest rutin content among the three methods, with a reflux time of 5–6 hours being optimal. Tu Yaosheng et al. [17] investigated the optimal process conditions for extracting rutin from Sophora japonica using the ethanol reflux extraction method. The results indicated that extracting Sophora japonica three times with 70% ethanol,each for 1 hour, followed by concentration of the extract to the point where no alcohol odor remained, allowing it to settle and form crystals, then centrifugation, and washing with water three times, resulted in a rutin purity of 89.82%. This method is relatively simple and feasible, yielding a product with low impurity levels and high yield; however, it requires a large amount of solvent and is costly, making it unsuitable for industrial production.

5 Supercritical Fluid Extraction Method

This method uses a fluid in a supercritical state as the solvent, which combines the advantages of both gases and liquids, enabling it to diffuse easily like a gas while possessing the solvent capacity of a liquid. Chen Shulai et al. [18] used supercritical CO₂ to extract rutin from Sophora japonica seeds. The results indicated that rutin has strong polarity and a large molecular weight, resulting in weak affinity with SC-CO₂, making direct extraction with supercritical CO₂ challenging.Therefore, pretreatment of the raw materials is necessary to enhance the affinity between rutin and SC-CO2, followed by extraction with SC-CO2 to obtain a crude extract.This method can be performed at room temperature without the need for organic solvents as extraction agents, thus avoiding environmental pollution. However, this method is suitable for extracting non-polar, low-molecular-weight substances. For the extraction of highly polar, high-molecular-weight substances like rutin, it is typically necessary to add an appropriate amount of a carrier agent to the supercritical fluid to enhance its solubility.

6 Ultrasonic extraction method

The ultrasonic extraction method utilizes the cavitation effect, mechanical effect, and thermal effect of ultrasonic waves to accelerate the release, diffusion, and dissolution of effective substances within cells, significantly improving extraction efficiency.

Zhang Zhulian et al. [19] found that the optimal operating conditions for extracting rutin using the ultrasonic extraction method were: treating the sample with ultrasonic waves at a frequency of 21.5 kHz for 10 minutes, followed by static incubation for 12 hours. Guo Xiaowu [20] compared the extraction efficiency of rutin from Sophora japonica seeds using the ultrasonic extraction method and the hot alkali extraction method.finding that the former did not require heating treatment and achieved high extraction rates with 30 minutes of ultrasonic treatment at 20 kHz, while the hot alkali method yielded the highest extraction rate after soaking for 32 minutes followed by boiling for 20 minutes, with extraction rates decreasing further with extended boiling time.

Ji Mei et al. [21] compared four rutin extraction methods—decoction, percolation, reflux, and ultrasonic extraction—and found that ultrasonic extraction was the most effective method, with the highest extraction efficiency and the highest purity of the rutin product obtained.Wei Jiangcun et al. [22] optimized three factors affecting the extraction of rutin from Sophora japonica using ultrasonic extraction: solvent concentration, solid-liquid ratio, and extraction time. The results indicated that the optimal conditions were 80% methanol concentration, a solid-liquid ratio of 0.1:50.0, and an extraction time of 40 minutes.In summary, the ultrasonic extraction method has advantages such as time-saving, energy-saving, and high extraction efficiency. However, currently, the ultrasonic extraction method is limited to laboratory operations and is rarely applied in industrial production.

7 Microwave-assisted extraction method

The principle of microwave-assisted extraction is that microwave energy rapidly penetrates the extraction medium, reaching plant cells. The moisture and intracellular contents within plant tissues rapidly increase in temperature, and the sustained high temperature elevates internal pressure, causing cell rupture and the release of intracellular contents. The target products are transferred from the cell interior to the extraction solvent.Pan Yuanyuan et al. [23] used microwave-assisted extraction to extract rutin from Sophora japonica seeds under optimal conditions: ethanol concentration of 65%, microwave time of 4 minutes, and microwave power of 320 W, achieving the best extraction results.Compared with traditional extraction techniques, microwave-assisted extraction has advantages such as high efficiency, rapidity, and good selectivity. However, this method is currently mainly limited to the extraction and analysis of samples in the laboratory and has been rarely applied in industrial production.

8結論

In summary, rutin plays a crucial role in the treatment of various diseases such as hypertension, hyperglycemia, and cardiovascular diseases. Although there are various methods for extracting rutin from Sophora japonica seeds, each has its own advantages and disadvantages.The alkali extraction and acid precipitation method requires heating for extraction, often resulting in the production of hydrolyzed products; the organic solvent extraction method is relatively complex, necessitating secondary recovery and treatment of the solvent, which is costly, yields lower purity of the extracted product, and poses risks of oxidation and solvent residue; while ultrasonic extraction and microwave-assisted extraction methods offer rapid and efficient advantages, they are not suitable for large-scale production.With the rapid development of extraction technology, it is believed that the extraction of rutin from Sophora japonica seeds can be achieved on a large scale in the near future.

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