GREEN RECOVERY OF POLYPHENOLS FROM NETTLE LEAVES (Urtica dioica L)

1Maras, M., 1Kruk, V., 2Radman, S., 1Dragović-Uzelac, V., 1Bursać Kovačević, D.

1Faculty of Food Technology and Biotechnology University of Zagreb, Pierottijeva 6, 10000, Zagreb, Croatia, dbursac@pbf.hr2Faculty of Agriculture, University of Zagreb, Svetošimunska 25, 10000, Zagreb, Croatia

Wild-growing and widespread annual plant with a great economic potential (1).

Used in a traditional medicine due to the content of various biologically active compounds (2).

Nettle can be used for production of plant extracts by conventional and/or novel extraction techniques (3).

Polyphenols in nettle offer many pharmacological effects (i.e. antioxidative, hypoglycemic, antiviral,

immunomodulatory etc.) (4).

Widespread application of nettle extracts in food, pharmaceutical, feed and other industries (5).

Urtica dioica L

THE AIM: To evaluate green recovery approach to valorize nettle leaves in terms of total phenolic content

Freeze-dried nettle leaves

ASE 350, Dionex, USAPLE nettle extracts

PLE parameters:Cycle number: 1, 2, 3, 4Static times: 5 and 10 minTemperature: 20 °C and 50 °C

Extraction solvent: 96% ethanol

Total phenolic content determination (TPC)Folin–Ciocalteu colorimetric method (8).

Pressurized Liquid Extraction (PLE) is a sample preparation technique that combines elevated temperature and pressure with liquid solvents to achieve fast and efficient extraction of the analytes from the solid matrix. The solvents are used near their supercritical region (high solubility and high diffusion rates of solutes in the solvent), while the high pressure keeps the solvent below its boiling point, and enables high penetration of the solvent in the sample (6, 7).

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

20 °C 50 °C 20 °C 50 °C

5' 10'

mg GAE/100G 106,44 131,86 139,74 170,01 315,51 439,63 501,01 576,58 204,63 261,79 284,41 303,81 409,11 547,86 623,73 739,97

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The averages for TPC in the nettle extracts ranged from 106,44 ± 0.11 to 739,97 mg GAE/g of dry material. Increased static time and cycle number promote higher extraction yields therefore the highest TPC was observed in nettle extracts obtained at 4 cycles and 10 min of static times. With respect to temperature, results showed a rise in TPC as extraction temperature increases (20 °C vs. 50 °C) probably due to more efficient degradation of cellular walls and easier release of bond phenolic compounds. However, statistic analysis found the highest yields of TPC under the following extraction conditions: extraction temperature of 50 °C and four 10 minute cycles for total phenols.

REFERENCES1. Di Virgilio, N., Papazoglou, E.G., Jankauskiene, Z.Di Lonardo, S., Praczyk, M., Wielgusz, K. (2015) Indian Crops Prod. 68, 42-49.2. Hojnik, M., Škerget, M., Knez, Ž. (2007) Sep. Purif. Technol. 57(1), 37-46.3. Ameer, K., Shahbaz, H.M., Kwon, J.H. (2017) Compr. Rev. Food Sci. F. 16(2), 295-315.4. Kregiel, D., Pawlikowska, E., Antolak, H. (2018) Mol. 23(7), 1664.5. Di Virgilio, N., Papazoglou, E.G., Jankauskiene, Z.Di Lonardo, S., Praczyk, M., Wielgusz, K. (2015) Indian Crops Prod. 68, 42-49.6. Putnik, P., Barba, F. J., Španić, I., Zorić, Z., Dragović-Uzelac, V., Kovačević, D. B. (2017) Food Bioprod. Process. 106, 19-28.7. Bursać Kovačević, D., Barba, F.J., Granato, D., Galanakis, C.M., Herceg, Z., Dragović-Uzelac, Putnik, P. (2018) Food Chemistry,254(2018), 150-157.8. Shortle, E., O'Grady, M.N., Gilroy, D., Furey, A., Quinn, N., Kerry, J.P. (2014) Meat Sci. 98(4), 828-834.

PLE could be considered as an advanced and promising green approach that could overcome current limitations of conventional extraction and provide valuable nettle extracts that could find their application in industry and in emerging global markets. The highest yields of TPC were observed under the following extraction conditions: extraction temperature of 50 °C and four 10 minute cycles for total phenols.

This work was supported by a grant from the Croatian Science Foundation, Croatia: Isolation and encapsulation of bioactive molecules of wild and cultivated nettle and fennel and effects on organism physiology (PlantBioPower, IP-01-2018-4924) .

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Results & Discussion

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