SELECTION OF A DEVICE TO ACCELERATE THE PHYTOEXTRACTION PROCESS

ABSTRACT

Phytoextraction is a subfield of solids extraction that deals with the extraction of components from plant materials. Areas of application of plant extracts are foods, pharmaceuticals, cosmetics and biocides. Plants contain a variety of components. Sometimes only a few components are of interest, sometimes complex mixtures of components.

АННОТАЦИЯ

Фитоэкстракция — это подраздел экстракции твердых веществ, который занимается экстракцией компонентов из растительных материалов. Области применения растительных экстрактов – пищевые продукты, фармацевтика, косметика и биоциды. Растения содержат различные компоненты. Иногда интерес представляют только несколько компонентов, иногда сложные смеси компонентов.

Keywords: phytoextraction, pharmacological effect, laboratory apparatus, plant material

Ключевые слова: фитоэкстракция, фармакологический эффект, лабораторная аппаратура, растительное сырье.

Other plant components have a pharmacological effect. Before the modern pharmaceutical industry brought standardized medicines with only one or a few active ingredients onto the market, such phytoextracts were the only available medicine for large parts of the population. However, fresh plants and herbs are only available at certain times of the year. Important methods of preservation were drying and soaking in alcohol or oil. The active ingredients from dried plants could be made available to the human organism by extraction with hot water, i.e. the preparation of a herbal tea. When plant material is placed in it, an extraction also takes place and the ingredients are transferred to the alcohol or oil. Many of these traditional extraction methods are still used today in the production of plant-based medicines [1, 2].

Phytoextraction is thus one of the oldest procedural processes. Nevertheless, many industrial phytoextraction processes are still based on experience and therefore have great optimization potential. The development of a generally applicable design strategy is made more difficult by the complexity of the plant material. The concentration of individual ingredients in the plant and their relationship to each other can be influenced by various influencing factors such as harvest time, weather conditions and soil conditions at the cultivation site. This makes it difficult to set the optimum process conditions in each case. Since there is often an interest in selectively extracting individual components from the plant material, a compromise between yield and selectivity must also be found. In order to be able to carry out the phytoextraction experiments in a comparable and reproducible manner, a standardized laboratory apparatus was developed by Delinski and Pfennig [2, 3, 4]. A flow diagram of their apparatus is shown in Fig. 1. The laboratory apparatus contains two different types of extractors: an immersion extractor and a percolation extractor. The immersion extractor can be operated continuously and discontinuously. The mechanisms of most of the extractors used in industry can be understood by testing these two laboratory extractors.

Figure 1. Flow chart of the standardized laboratory equipment from Delinski et al.

A comparable apparatus was set up as part of this work. As can be seen in Fig. 2, the two extractors and the solvent tank are in a temperature-controlled water bath. The temperature in the water bath is controlled by a thermostat (Lauda, type M3). The thermostat is counter-cooled via a water connection.

An HPLC pump (Kontron Analytic, type LC Pump 410) is used to convey the solvent from the solvent tank into the percolation and immersion extractor. The vessels are connected to each other via Teflon hoses. An MR 2002 magnetic stirrer from Heidolph is used as the stirrer in the immersion extractor.

Figure 2. Laboratory equipment for phytoextraction

The percolation extractor is a fixed bed extractor and is operated with solvent from the tank. The extractor consists of a 110 mm long glass tube (from DeDietrich, type M-PSGL14/110) with GL14 threads on both sides. The extractor can be connected to the pump and the solvent tank via GL laboratory screw connections. If the plant material is smaller than the diameter of the hose, there is a risk that parts of the heap will be discharged. In such cases, the plant material was heaped onto a glass fiber filter.

The immersion extractor is manufactured by NORMAG Labor- und Prozesstechnik GmbH. The glass container with a nominal diameter of DN 60 and a flat bottom has a capacity of 300 ml. The container is connected to a flat flange lid with a quick-release fastener. The lid has three GL14 connectors. In order to avoid the discharge of the solid particles during continuous operation, an immersion filter was attached to the outlet hose. Replaceable glass fiber microfilters (Whatman, type GF/D, 25 mm) were attached to the filter holder. The glass fiber filters were also used for sampling in a syringe filter. Wide-necked laboratory bottles with a nominal volume of 250 ml were used as the second immersion extractor.

Figure. 3. Concentration-time curve as a function of the ethanol content of the solvent using lemon balm as an example

In a series of tests, lemon balm was extracted with ethanol-water mixtures of different concentrations in a stirred tank. The measured concentrations were based on the solid/solvent ratio. The concentration-time curves of the rosmarinic acid concentration in the solvent are plotted in Fig. 3. With 0% ethanol, i.e. pure water, the concentration of rosmarinic acid in the solvent increases with increasing extraction time and approaches a constant value after approx. 2000 s. With increasing ethanol content, the yield increases, reaches a maximum at 20% and then decreases again. The minimum is reached with 100% ethanol. Furthermore, the extraction is slower. With higher ethanol contents, the equilibrium is not reached in the test period. The dependency on the solvent composition can be clearly seen here. The highest concentration at the end of the experimental period was achieved with 30% ethanol. The amount of substance extracted decreases with a higher ethanol content and approaches a minimum with pure ethanol. With an ethanol/water mixture, the yield can therefore be improved compared to the pure solvents. This is particularly interesting since the polarity of rosmarinic acid calculated with VCCLAB is 1.25-2.82. So the solubility in ethanol should be higher than the solubility in water. The polarity should therefore not be the sole evaluation criterion when selecting the solvent. The choice of solvent should be supported by laboratory experiments.

References:

1. Bart H.J., Hagels H.J., Kassing M., Johannisbauer W., Jordan V., Pfeiffer D., Pfennig A., Tegtmeier M., Schäffer M., Strube J.: Positionspapier der ProcessNet Fachgruppe „Phytoextrakte – Produkte und Prozesse“, Vorschlag für einen neuen, fachübergreifenden Forschungsschwerpunkt, 2012
2. Delinski D., Bol J.B., Pfennig A. Plant-material extraction in a standardised laboratory apparatus using optimal experimental design. International Solvent Extraction Conference Proceedings, Santiago de Chile, 2011
3. Султанова Ш.А. Усенов А.Б. Использование аналитически-расчетного метода для описания движения элементов потока в экстракторе сокслет // Universum: технические науки: электрон. научн. журн. 2020. 11(80).
4. Султанова Ш.А. Усенов А.Б. Получение данных температурной зависимости растворимости спирта при экстракции растения базилика обыкновенного (ocimum basilicum). // Universum: технические науки: электрон. научн. журн. 2020. 11(80).