The process of Centella Asiatica extract has been researched and practiced for many years, and there are many different processes. The following is a brief introduction to these processes:
1 Ethanol extraction method
Luo et al. [1] reported a simple method for extracting active substances from Centella Asiatica in 1980. In this experimental method, 95% ethanol was used as a solvent to obtain asiaticoside from the Centella Asiatica extract by extraction. This is the first report on the extraction and separation of Centella Asiatica extract in China. The application value of Centella Asiatica has been continuously put forward by researchers in recent years, and its related extraction and purification methods have also been further studied.
2 Ultrasonic extraction method
Chen[2] et al. reported a systematic study on the extraction of total asiaticoside using three extraction methods: ultrasonic, reflux, and soaking respectively. The orthogonal design method was used in the experiment to select the optimal extraction conditions for the extraction of total asiaticoside. The concentration of 75% ethanol was ultrasonically extracted for 1 h, and the total asiaticoside content reached the maximum value. The extraction conditions used were amplified to 20 times the amount for extraction, and the content of total asiaticoside was 1.25%. It shows that the preparation process is fully feasible.
Chen[3] et al reported a method for optimizing the extraction process of Centella Asiatica by Taguchi experimental design. In this experimental method, the content of asiaticoside and the transfer rate of asiaticoside were investigated as indicators, and the optimal extraction process conditions were 75% ethanol concentration and 1h reflux extraction time. Under this extraction condition, the transfer rate of asiaticoside was 72.3%, which was superior to other reported experimental results, and provided a reliable basis for industrial production.
3 Acid-base extraction method
Hou[4] et al reported a method for extracting the whole plant of Centella Asiatica by using the acid-base method in the cell disruption method. The extraction rate of this method is higher than that of traditional ethanol extraction. After the dried Centella Asiatica is crushed, accurately weigh the Centella Asiatica powder. The material ratio of the Centella Asiatica powder and the solvent is 1:10. The extraction solution is an ethanol solution with a concentration of 75%, and HCl is used to adjust the pH value to 2-6 The pH value was adjusted to 8-12 with NaOH, and the product total asiaticoside was obtained after a series of reflux and extraction.
4 Enzyme extraction method
Han[5] et al reported a method for extracting asiaticoside in Centella Asiatica by using the enzyme extraction method. In this experiment, factors such as the type, dosage, initial pH of enzymolysis solution, enzymolysis temperature, the material-liquid mass ratio of Centella Asiatica and solvent water, enzymolysis time and other factors were investigated, and an orthogonal experimental design was used to screen out the enzymes. Solve the optimal process parameters. Compared with the traditional ethanol extraction method, the enzymatic extraction method has the advantages of a fast extraction rate, mild process conditions, and high yield, which is a good extraction method.
5 Decoction extraction method
Lu[6] et al. reported a decoction extraction method for process optimization by orthogonal experiment and determination of madecassoside content by thin-layer chromatography scanning method. In this method, water is used instead of ethanol as the extraction solvent, and chitosan is added to the extract for purification. The method has the advantages of saving raw materials, shortening man-hours, and reducing costs, and is beneficial to the modern industrial production of Centella Asiatica extract.
6 Near-critical water extraction methods
Wan[7] et al. reported a method for extracting asiaticoside and Asiatic acid from Centella Asiatica using near-critical water as the extraction solvent. The method measures the extraction yields of Asiatic acid and asiaticoside using high-performance liquid chromatography (HPLC) at temperatures from 100 to 250 °C and pressures from 10 to 40 MPa. In this experiment, the extraction rates of Asiatic acid and asiaticoside increased with increasing extraction temperature or pressure. The extracted Asiatic acid and asiaticoside can be collected as particles from the water in a simple filtration process. The extraction yields of asiaticoside and Asiatic acid at 40 MPa and 250 °C using near-critical water were higher than those using conventional liquid solvents (methanol or ethanol) at room temperature.
7 Microwave-assisted extraction
Wang[8] et al. reported a microwave-assisted method to extract flavonoids from Centella Asiatica, and the optimal extraction process was determined by an orthogonal experiment. Weigh the naturally dried Centella Asiatica powder, filter it through a 100-mesh sieve, place the sieved Centella Asiatica powder in a Soxhlet extractor, and carry out continuous reflux degreasing and decolorization with petroleum ether, and finally, the obtained sample is ventilated and dried for later use. Accurately weigh the Centella Asiatica powder obtained, add methanol according to the ratio of material to liquid 1: 10, place it in a conical flask, extract 3 times intermittently, combine the extracts, evaporate to dryness under reduced pressure, dissolve in methanol and place the In a 100mL volumetric flask, the final product, Centella Asiatica extract, was obtained.
8 Supercritical CO2 extraction method
Reverchon[9] et al. reported the extraction of weakly polar components from Centella Asiatica by supercritical extraction. This method has the advantages of high extraction efficiency and high extraction selectivity. It is an environmentally friendly green extraction method and is suitable for the separation of heat-sensitive Substances and inseparable systems of matter. The main disadvantage of this method is that the extraction of polar components is highly limited by the poor solvent ability of supercritical CO2 for polar components.
References:
[1] Luo S Q, Chin H F. Isolation and identification of asiaticoside from Centella asiatica (L.) Urban[J]. Chin Trad Herb Drugs, 1980, 11: 244-246.
[2] Chen Yao, Han Ting, Qin Luping, Zheng Hanchen. Orthogonal design method to optimize the extraction technology of Centella Asiatica [J]. Chinese Materia Medica, 2003, 26(3): 204-205.
[3] Chen Yi, Gao Wenyuan, Yu Quanlin, Chen Haixia. Taguchi's experimental design method to optimize the extraction process of Centella asiatica[J]. China Journal of Traditional Chinese Medicine, 2007, 32(6): 1714-1716.
[4] Hou Wenyan, Shen Ning, Gao Renxiao. Study on the extraction process of Centella asiatica[J]. Applied Chemical Industry, 2011, (32) 04: 679-681.
[5] Han Wei, Chen Huidan, Fan Liang, Wang Chunli. Enzymatic extraction of Centella asiatica[J]. Journal of the Nanjing University of Technology, 2009 31(3): 18-22.
[6] Lu Maofang, Li Ruocun, Peng Xinjun, Zhan Kuo. Study on the extraction and purification process of Centella asiatica[J]. Journal of Hunan University of Traditional Chinese Medicine, 2007, 27(1): 16-19.
[7] Kim W J, Kim J, Veriansyah B, et al. Extraction of bioactive components from Centella Asiatica using subcritical water[J]. The Journal of Supercritical Fluids, 2009,48(3): 211-216.
[8] Reverchon E, De Marco I. Supercritical fluid extraction and fractionation of natural matter[J]. The Journal of Supercritical Fluids, 2006, 38(2): 146-166.
