Extraction of compounds of interest from bio-based materials
Extraction of compound(s) of interest covers a broad spectrum of applications in the laboratory and industrial field: from natural active ingredients (e.g. flavours, pigments, oils, vitamins, antioxidants, proteins, etc.) for pharmaceutical and food industry to contaminants and environmental pollutants (pesticides, polycyclic aromatic hydrocarbons – PAHs, polychlorinated biphenyls – PCBs, etc.) for environmental authorities. Bio-based or environmental materials (e.g. plant tissues, wood, soil) include various components whose interaction can cause undesired interferences and result in misinterpretations in quantitative and/or qualitative analyses.
The main purpose of extraction techniques is thus to gain analyte compounds (or more compounds of interest):
- in high yield;
- with highest purity without interferencing compounds;
- with low waste; and
- with low energy/time consumption at the same time.
In general, extraction techniques are based on a separation principle, „like dissolves like“, so for selecting an appropriate extraction system, the following conditions are crucial: solvent type, sample/solvent ratio, temperature, pressure, extraction duration and number of extraction cycles.
Common techniques use solid or semi-solid samples, so compounds of interest are dissolved into suitable solvents or more solvents in a row (solid-liquid extraction) or are proceeded in liquid form within liquid-liquid extraction. Liquid-liquid extractions are often performed to purify the analyte. However, this separation is possible only when the compound(s) of interest is soluble in a different solvent than the undesired compound(s). At the same time, those two solvents have to be mutually immiscible. The extraction procedures might be combined in sequences as a part of the purification step or to concentrate the amount to increase the analyte detectability.
More advanced techniques belong solid-phase extraction (SPE) using retention of analyte on a sorbent; accelerated-solvent extraction (ASE); ultrasound-assisted extraction (UAE); microwave-assisted extraction (MAE); enzyme-assisted extraction; and supercritical fluid extraction (SFE) by application of supercritical carbon dioxide.
The conventional solid-liquid extraction system counts the Soxhlet apparatus. A more sophisticated system that offers time-planning is an updated Soxhlet - PC-controlled extraction system fexIKA. A more time-effective system is accelerated-solvent extraction (ASE). It is an automated solid-liquid extraction system that uses 100 times higher pressure than conventional techniques and therefore enables low solvent consumption with the advantage of considerably shorter extraction time.
Below are a few application examples for analytes from natural products, where ASE was applied:
Source |
Analytes |
Solvent |
Temperature (°C) |
Static extraction time (min) |
Number of extraction cycles |
Reference |
wild nettle (Urtica dioica L.) leaves |
polyphenols, pigments |
ethanol (96%) |
20; 50; 80; 110 |
5; 10 |
1; 2; 3; 4 |
|
sorghum bran |
polyphenols, antioxidants |
50 and 70% (v/v) ethanol |
60; 120; 150 |
1 |
1 |
|
grape skin pomace |
polyphenols, antioxidants |
50% ethanol |
50 |
15 |
2 |
|
carrots |
carotenoids, polyphenols |
ethanol |
40–120 |
20–60 |
1–3 |
|
red cabbage |
pigments |
water/ethanol/ |
80; 100; 120 |
1–5 |
1 |
|
rape seeds (canola) |
oil |
petroleum ether |
105 |
10 |
3 |
Kettle, n.d. |
brewer's spent grain |
proteins |
NaOH |
40; 60; 80 |
5; 15; 30 |
4 |
|
vanilla beans |
vanilla flavor |
ethanol; |
room temperature; 50; 100 |
3; 10; 20 |
1; 3 |
|
alfalfa and citrus leaves |
pesticides |
ethyl acetate/ |
80 |
10 |
3 |
Further information:
- Arapitsas, P., and Turner, C. (2008). Pressurized solvent extraction and monolithic column-HPLC/DAD analysis of anthocyanins in red cabbage. Talanta 74, 1218–1223. doi: 10.1016/j.talanta.2007.08.029.
- Barros, F., Dykes, L., Awika, J. M., and Rooney, L. W. (2013). Accelerated solvent extraction of phenolic compounds from sorghum brans. Journal of Cereal Science 58, 305–312. doi: 10.1016/j.jcs.2013.05.011.
- Cicchetti, E., and Chaintreau, A. (2009). Comparison of extraction techniques and modeling of accelerated solvent extraction for the authentication of natural vanilla flavors. J of Separation Science 32, 1957–1964. doi: 10.1002/jssc.200800650.
- Junttila, M. H. (2022). Extraction of brewers’ spent grain in near subcritical conditions: A method to obtain high protein contents extracts. Journal of Agriculture and Food Research 10, 100378. doi: 10.1016/j.jafr.2022.100378.
- Kettle, A. (n.d.). Thermo Scientific Application Note 325: Extraction of Oil Content from Oilseeds by Accelerated Solvent Extraction.
- Kinross, A. D., Hageman, K. J., Doucette, W. J., and Foster, A. L. (2020). Comparison of Accelerated Solvent Extraction (ASE) and Energized Dispersive Guided Extraction (EDGE) for the analysis of pesticides in leaves. Journal of Chromatography A 1627, 461414. doi: 10.1016/j.chroma.2020.461414.
- Li, J., Zhang, S., Zhang, M., and Sun, B. (2019). Novel approach for extraction of grape skin antioxidants by accelerated solvent extraction: Box–Behnken design optimization. J Food Sci Technol 56, 4879–4890. doi: 10.1007/s13197-019-03958-5.
- Repajić, M., Cegledi, E., Kruk, V., Pedisić, S., Çınar, F., Bursać Kovačević, D., et al. (2020). Accelerated Solvent Extraction as a Green Tool for the Recovery of Polyphenols and Pigments from Wild Nettle Leaves. Processes 8, 803. doi: 10.3390/pr8070803.
- Šeregelj, V., Tumbas-Šaponjac, V., Mandic, A., Cetkovic, G., Čanadanovic-Brunet, J., Vulic, J., et al. (2018). Accelerated solvent extraction of bioactive compounds from carrot: Optimization of response surface methodology. J Serb Chem Soc 83, 1223–1228. doi: 10.2298/JSC180531068S.