Background: Camellia sinensis is a plant whose leaves and buds are used to produce tea. With many medicinal activities already found, green tea has been consumed widely in the world. Methods: The subcritical water extraction (SWE) of epigallocatechin gallate (EGCG) from green tea leaves and the effect of the different extraction conditions are investigated by response surface methodology (RSM). Furthermore, the model of the extraction processes is reviewed for application at the industrial scale. Results: Based on the RSM data, the maximum yield of extraction is determined via optimizing different parameters of the extraction processes. Optimal conditions are as follows: extraction time of 6 min, extraction temperature at 120 °C, and a sample/solvent ratio of 1:40 g/mL. Under such conditions, the best yield of EGCG is 4.665%. Moreover, the model of the extraction processes, which can be utilized for industry scale purpose, indicates a good correlation with the experimental data. Conclusions: Overall, SWE is competent and environmental-friendly, and it is also a highly selective and fast method. SWE is a promising method to take the place of organic solvents used in the extraction of weak polar and even non-polar natural compounds. Further studies on the scale-up of the extraction processes are ongoing.

This study develops a high performance liquid chromatography with ultraviolet detection (HPLC-UV) for simultaneous quantification of hederacoside C and α-hederin in Hedera nepalensis K. Koch. The method proposed in this study was validated in terms of the analytical parameters such as high repeatability, high accuracy and good sensitivity. The method was used to determine the content of hederacoside C and α-hederin in Hedera nepalensis K. Koch, which had been collected in Ha Giang, Lao Cai and Lai Chau. The study results show that the content of hederacoside C and the content of α-hederin ranged from 0.40 to 4.01% and 0.21 – 0.54% based on absolute dry mass, respectively. Keywords Hedera nepalensis K. Koch, hederacoside C, α-hederin, HPLC-UV. References [1] L. Jafri, et al, In vitro assessment of antioxidant potential and determination of polyphenolic compounds of Hedera nepalensis K. Koch, Arabian Journal of Chemistry. 10 (2017) 3699-3706. https://doi.org/10.1016/j.arabjc.2014.05.002.[2] S. Saleem, et al, Plants Fagonia cretica L, and Hedera nepalensis K. Koch contain natural compounds with potent dipeptidyl peptidase-4 (DPP-4) inhibitory activity, Journal of ethnopharmacology. 156 (2014) 26-32. https://doi.org/10.1016/j.jep.2014.08.017[3] D.H. Bich, Medicinal plants and animals for medicine in Vietnam, Vol 1, Science and Technics Publishing House, Hanoi, 2006 (in Vietnamese).[4] National Institute Of Medicinal Materials, List of medicinal plants in Vietnam, Science and Technics Publishing House, Hanoi, 2016 (in Vietnamese).[5] L. Jafri, et al, Hedera nepalensis K. Koch: A Novel Source of Natural Cancer Chemopreventive and Anticancerous Compounds, Phytotherapy research. 30(3) (2016) 447-453. https://doi.org/10.1002/ptr.5546. [6] S. Kanwal, et al, Antioxidant, antitumor activities and phytochemical investigation of Hedera nepalensis K. Koch, an important medicinal plant from Pakistan, Pakistan Journal of Botany. 43 (2011) 85-89. [7] G. Uddin, et al, Biological screening of ethyl acetate extract of Hedera nepalensis stem, African Journal of Pharmacy and Pharmacology. 6(42) (2012) 2934-2937. https://doi.org/10.5897/AJPP12.828 [8] H. Kizu, et al, Studies on Nepalese Crude Drugs, III, On the Saponins of Hedera nepalensis K. Koch, Chemical and Pharmaceutical Bulletin. 33(8) (1985) 3324-3329. https://doi.org/0.1248/cpb.33.3324[9] X. Tong, et al, Extraction and GC-MS Analysis of Volatile Oil from Hedera nepalensis var sinensis, Fine Chemicals. 24(6) (2007) 559-561. [10] EDQM, European Pharmacopoeia, fifth ed., Council of Europe, France, 2015. [11] N.T.H. Mai, et al, Simultaneous Quantification of Hederacoside C and α-Hederin from the Leaves of Hedera helix L. by HPLC, Journal of Medicinal Material. 21(6) (2016). (in Vietnamese).[12] L. Havlíková, et al, Rapid Determination of α-Hederin and Hederacoside C in Extracts of Hedera helix Leaves Available in the Czech Republic and Poland, Natural product communications. 10(9) (2015). https://doi.org/10.1177/1934578X1501000910[13] M. Yu, et al, Determination of Saponins and Flavonoids in Ivy Leaf Extracts Using HPLC-DAD, Journal of Chromatographic Science. 53(4) (2014) 478-483. https://doi.org/10.1093/chromsci/bmu068.[14] EMEA, Validation of analytical procedures: text and methodology Q2 (R1), in International conference on harmonization, Geneva, Switzerland, 2005. [15] W. Horwitz, Official methods of analysis, 12 ed., Vol 1, Association of Official Analytical Chemists, Washington DC, 1975.

(1) Background: Hedera nepalensis (Araliaceae) is a recognized medicinal plant founded in Asia that has been reported to work in antioxidant, antifungal, antimicrobial, and antitumor capacities. (2) Methods: The subcritical fluid extraction of saponin from Hedera nepalensis leaves and the optimum of the extraction process based on yield of saponin contents (by calculating the hederacoside C contents in dried Hedera nepalensis leaves) are examined by response surface methodology (RSM). Furthermore, the antimicrobial activity of the extract is tested for potential drug applications in the future. (3) Results: Based upon RSM data, the following parameters are optimal: extraction time of 3 min, extraction temperature of 150 °C, and a sample/solvent ratio of 1:55 g/mL. Under such circumstances, the achieved yield of saponin is 1.879%. Moreover, the extracts inhibit the growth of some bacterial strains (Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenza) at a moderate to strong level with inhibition zone diameter values ranging from 12.63 to 19.50 mm. (4) Conclusions: The development of such a model provides a robust experimental process for optimizing the extraction factors of saponin contents from Hedera nepalensis extract using subcritical fluid extraction and RSM. Moreover, the current work reveals that saponin extracts of Hedera nepalensis leaves exhibit a potential antimicrobial activity, which can be used as scientific evidence for further study.

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