Extraction And Separation Of Active Components From Centella Asiatica

Centella asiatica is a traditional herb with a variety of pharmacological activities and widely used in Asia and South Africa. However, the active ingredients responsible for the activities are not clear yet because of difficulties in purification of active components. This fact limits the further application of Centella asiatica. Therefore, the research on extraction and separation of active components from Centella asiatica is necessary.Centella asiatica total triterpenoid saponins is a polar part of Centella asiatica and has healing property, anti-bacterial activity, anti-inflammatory activity and so on. It mainly contains three active triterpenes, namely, asiaticoside, madecassoside, and asiaticoside-B. However, their separation still remains a challenge due to their similar structures and polarities. This work reported a new separation technique-the Simulated Moving Bed chromatography (SMB). Asiaticoside, madecassoside and asiaticoside-B were successfully separated and prepared by two stages from Centella asiatica total triterpenoid saponins using SMB. The purities of asiaticoside, madecassoside, and asiaticoside-B obtained were 98.7%,87.62% and 81.77%, respectively, and their corresponding recoveries were 93.5%,80.66% and 83.67%. This technique provided a simple and effective method for the preparation of asiaticoside, madecassoside, and asiaticoside-B.There are few reports about the nonpolar part of Centella asiatica, but they have been proven to exhibit anti-depressant, antimicrobial, antioxidant activities and gained great interests. In this work, supercritical CO2 extraction technology was used to extract essential oil from Centella asiatica at 60℃and 30 MPa. A brown scented extract with 2%(w/w) yield was obtained. Compounds in the extract such as hexadecanoic acid, octadecanoic acid and 9,12-octadecadienoic acid(Z,Z) were indirectly inferred according to their acid value, saponification value, the ability of esterification reaction with methanol and their gas chromatographies. Antidepressant activity of the extract was testified by zoopery. Antioxidant activity was measured by DPPH method and the half maximal inhibitory concentration (IC50) was 4.985 mg/mL.Considering the extract contains various components, liquid chromatography on silica gel was used to separate the extract. Dichloromethane was used as the mobile phase and the concentrated effluent were identified by GC-MS. The results show that the extract contains 27 compounds including unsaturated short-chain olefin, long-chain fatty acids and aliphatic ester, from which a pure compound named as di-n-octyl phthalate was identified. Moreover, another effluent with the highest antioxidant activity was used to separate by column chromatography on silica gel and hexane as mobile phase. A pure compound with structure of (E)-7,11-dimethyl-3-methylene-1,6,10-triene, also known as farnesene, was obtained.