Kerry Ferguson Research Series Botanical Science & Innovation
Research Paper | 2026
Citation: Ferguson, K. (2026). Green Extraction of Botanical Bioactive Compounds: Technologies, Opportunities and Technical Challenges. Kerry Ferguson Research Series Botanical Science & Innovation.
Abstract
The extraction of bioactive compounds from plants is central to the manufacture of botanical ingredients for pharmaceutical, nutraceutical, food, beverage and personal-care applications. Conventional extraction technologies can provide effective recovery of plant constituents, but increasing environmental, regulatory and commercial pressures have encouraged the development of processes that reduce hazardous solvent use, energy demand, processing time and waste while preserving chemically sensitive phytochemicals.
The term green extraction encompasses a broad range of approaches rather than a single manufacturing technology. These include the use of water, ethanol and other comparatively low-impact solvent systems; ultrasound-assisted extraction; microwave-assisted extraction; pressurised and subcritical water extraction; supercritical-fluid extraction; enzyme-assisted extraction; natural deep eutectic solvents and combinations of these technologies.
The scientific challenge is not simply to maximise extraction yield. Botanical materials contain chemically diverse constituents whose polarity, solubility, stability and interactions with the plant matrix differ substantially. Process conditions capable of increasing total extract yield may not maximise recovery of a desired bioactive compound and may simultaneously increase degradation, co-extraction of undesirable material or downstream processing complexity.
This paper examines green extraction from the perspective of botanical ingredient development. It considers solvent selection, mass transfer, ultrasound, temperature, oxygen exposure, extraction selectivity, scale-up and downstream concentration and stabilisation. Particular emphasis is placed on the need to evaluate extraction as part of an integrated manufacturing system rather than as an isolated processing step.
The evidence supports a compound-targeted and matrix-specific approach in which extraction efficiency is evaluated alongside chemical integrity, selectivity, solvent recovery, energy consumption, process scalability and final ingredient stability.
Introduction
Extracting useful compounds from plants appears conceptually simple.
Plant material is contacted with a solvent, soluble constituents move from the botanical matrix into the liquid phase, the plant solids are separated and the resulting extract is concentrated or processed into an ingredient.
In practice, botanical extraction is considerably more complex. Plants contain chemically diverse compounds distributed across cellular structures and associated with proteins, polysaccharides, lipids, fibres and other components of the plant matrix.
Target compounds may range from highly polar phenolic acids and flavonoids to comparatively lipophilic terpenoids, volatile compounds and oils. No single solvent or extraction technology is therefore optimal for every botanical material or every target compound.
This creates the central question of botanical extraction: How can compounds of interest be recovered efficiently while minimising degradation, unnecessary solvent use, undesirable co-extraction and downstream processing complexity? The increasing interest in green extraction technologies represents an attempt to answer this question while also improving environmental and manufacturing performance.
What Is Green Extraction?
Green extraction is often described in environmental terms: reducing hazardous solvents, energy consumption, processing time and waste.
These objectives are important, but they represent only part of the issue. A genuinely useful green extraction process must also produce an extract suitable for its intended commercial application. A process that uses less solvent but destroys a thermally sensitive bioactive compound is not necessarily an improvement. Likewise, a technology that produces exceptionally high total extraction yield but also extracts excessive chlorophyll, waxes, proteins, sugars or other unwanted material may increase purification requirements and energy consumption later in the process.
Green extraction should therefore be considered across the complete manufacturing system. Important objectives include: reduction of hazardous solvent use; greater use of renewable or food-compatible solvents; reduced energy consumption; shorter extraction times; improved target-compound recovery; preservation of sensitive compounds; reduced waste generation; solvent recovery and reuse where appropriate; commercially practical scale-up; and production of an extract suitable for subsequent concentration, purification and stabilisation. Green extraction is therefore better viewed as a process-design philosophy than as a particular piece of equipment.
Extraction Begins with the Botanical Matrix
The efficiency of an extraction technology cannot be considered independently of the botanical starting material.
Different plant tissues have different structural characteristics. Leaves, bark, roots, seeds, flowers, fruits and woody tissues differ in cellular structure, fibre composition, moisture, oil content and accessibility of intracellular compounds.
Particle-size reduction can increase available surface area and improve solvent contact. However, increasingly fine milling can also create practical problems including difficult filtration, increased oxidation, excessive extraction of fine particulate material and increased processing energy. Drying conditions may alter the botanical material before extraction even begins. Temperature, oxygen and light exposure during drying and storage can influence the concentration and chemical state of sensitive phytochemicals.
Consequently: extraction optimisation cannot compensate completely for poorly characterised or degraded botanical starting material. This connects extraction directly with the wider standardisation framework considered in the first paper in this series.
Solvent Polarity and Chemical Selectivity
Solvent selection is one of the most important determinants of botanical extraction. The principle of chemical similarity often simplified as “like dissolves like” means that compounds differing in polarity exhibit different solubilities in different solvent systems.
Water effectively extracts many highly polar constituents. Alcohols such as ethanol extend the range of compounds that can be recovered and are widely used in botanical preparations. Vegetable oils can provide a useful phase for comparatively lipophilic compounds. Other solvent systems may provide still different selectivity.
The appropriate question is therefore not: Which solvent produces the highest extract yield? but: Which solvent system selectively recovers the desired chemical profile while remaining compatible with the intended downstream process and commercial application? This distinction is fundamental. A large quantity of extract is not necessarily a high-quality extract.
Water as an Extraction Solvent
Water has obvious advantages as a botanical extraction medium. It is inexpensive, widely available, non-flammable and compatible with many food, nutraceutical and pharmaceutical applications. It is particularly useful for hydrophilic compounds.
However, water also presents important limitations. It may extract substantial quantities of sugars, proteins, polysaccharides, minerals and other highly polar components that are not always desired in concentrated botanical ingredients.
Water-rich extracts can also create significant downstream energy requirements because large quantities of water must be removed during concentration or drying.
Microbiological stability can become another consideration where aqueous extracts are stored before further processing.
Consequently, the environmental advantage of water during extraction should not be evaluated without considering the energy required to remove that water later. This illustrates an important principle of green processing: the environmental cost of a solvent cannot be assessed solely at the extraction stage.
Ethanol and Aqueous Ethanol
Ethanol occupies an important position in botanical extraction because it combines relatively broad solvent capability with established use in food, pharmaceutical and herbal preparations. Blending ethanol with water changes solvent polarity and can substantially alter the profile of extracted compounds. This makes aqueous ethanol particularly useful for phenolic and other medium-polarity constituents.
Published studies repeatedly demonstrate that ethanol concentration can materially affect recovery of phenolic compounds. For example, comparative work on sage using ultrasound- and microwave-assisted extraction demonstrated that solvent composition was a significant process variable influencing phenolic recovery. The existence of an optimum solvent composition for one particular plant and analytical target should not, however, be treated as a universal formulation.
The optimum system will depend upon: target compound; botanical species; plant part; moisture; particle size; extraction technology; temperature; processing time; and desired composition of the finished extract.
Published optimisation studies are therefore most useful for demonstrating relationships between variables, rather than providing universal manufacturing recipes.
Vegetable Oils and Lipophilic Extraction
Vegetable oils provide another potentially valuable approach for extracting lipophilic botanical compounds. They can offer advantages where the target compound is oil-soluble and where the final ingredient can incorporate an oil phase. This approach can potentially reduce the requirement for volatile organic solvents and may enable extraction and formulation to be partially integrated.
However, vegetable-oil extraction creates its own technical questions. The oil may itself oxidise. Its viscosity may slow mass transfer. Separation of plant solids can be more difficult. The resulting extract may require emulsification or encapsulation if it is subsequently converted into a water-dispersible or powdered ingredient. The carrier oil also becomes part of the final chemical composition. Oil extraction is therefore not simply a solvent substitution. It can fundamentally change the architecture of the ingredient being manufactured.
Ultrasound Assisted Extraction
Ultrasound-assisted extraction has become one of the most extensively investigated green extraction technologies for plant bioactive compounds. Ultrasonic energy passing through a liquid can create acoustic cavitation — the formation, growth and collapse of microscopic bubbles. These events can create localised shear, turbulence and disruption at the surface of plant material.
The practical effects can include: improved solvent penetration; increased contact between solvent and plant tissue; disruption of cellular structures; increased mass transfer; and shorter extraction times.
Research and reviews of plant-based systems report that ultrasound-assisted extraction can reduce solvent and energy requirements and improve recovery of compounds including phenolics and flavonoids under appropriate conditions. These advantages explain its growing commercial interest. They should not, however, lead to the assumption that increasing ultrasonic intensity automatically improves an extraction.
Ultrasound Is a Process Variable, Not a Guarantee
Ultrasound-assisted extraction depends on interacting variables including: frequency; power or energy density; equipment geometry; solvent composition; botanical concentration; temperature; treatment time; and physical characteristics of the plant material. The resulting extraction therefore reflects a multidimensional system.
Published optimisation studies illustrate these interactions. Experimental research on sage has shown that ultrasound-assisted extraction performance changes according to solvent composition and extraction time. Similar studies across other plant materials demonstrate significant interactions between ultrasonic power, extraction temperature, time and solid-to-liquid ratio.
The implication for commercial botanical processing: ultrasonication should be optimised for the target chemical system rather than applied as a generic processing treatment.
The Risk of Degradation
Green extraction technologies are frequently promoted for their ability to operate at lower temperatures and shorter treatment times than conventional extraction.
This can be beneficial for thermally sensitive compounds.
However, chemical degradation is not controlled by temperature alone. Phenolic compounds, terpenes, pigments and other phytochemicals may also be affected by oxygen, light, pH, metal ions and reactive chemical species.
Ultrasonic cavitation itself creates highly energetic local environments. The net result can vary according to the compound and extraction system. Research evaluating ultrasound-assisted extraction therefore increasingly considers not only extraction efficiency but also possible chemical transformation and safety implications.
The correct optimisation objective is consequently not simply: maximum extraction but rather: maximum useful recovery of chemically intact target compounds.
Temperature: Extraction Accelerator and Degradation Risk
Increasing temperature can improve extraction in several ways. Higher temperatures may increase solubility, reduce solvent viscosity, improve diffusion and accelerate mass transfer. At the same time, temperature can accelerate oxidation, hydrolysis, volatilisation and other degradation pathways.
The optimum temperature therefore represents a compromise. For robust compounds, higher temperatures may produce efficient extraction. For thermally sensitive compounds, lower-temperature processing may preserve chemical integrity even where extraction proceeds more slowly. Temperature also interacts with solvent composition and extraction technology. For example, ultrasonic processing itself may increase bulk liquid temperature during operation. Commercial systems must therefore control actual process temperature, rather than assuming that a nominally non-thermal technology operates without thermal effects.
Time and Residence Period
Conventional botanical extraction frequently relies on prolonged solvent contact. Increasing extraction time can initially increase compound recovery as mass transfer proceeds towards equilibrium. Eventually the incremental benefit decreases. Extended residence time may then provide little additional extraction while increasing exposure to oxygen, temperature and other degrading conditions.
This creates another important principle: longer extraction is not necessarily better extraction. Assisted extraction technologies are commercially attractive partly because they can accelerate mass transfer and reduce the time required to reach useful recovery. However, the optimum residence period remains matrix- and compound-specific.
Plant to Solvent Relationships
The relationship between botanical material and extraction solvent influences both extraction performance and manufacturing economics. Insufficient solvent may limit mass transfer and create poor mixing. Very high solvent volumes may improve extraction but increase solvent purchase, handling, recovery and concentration costs.
Laboratory optimisation often identifies conditions that maximise analytical recovery. Commercial manufacturing must solve a more difficult problem: what plant-to-solvent relationship provides acceptable recovery, selectivity and reproducibility at an economically and environmentally practical solvent volume? This represents one of the common challenges in translating laboratory extraction research into industrial production.
Microwave Assisted Extraction
Microwave-assisted extraction uses electromagnetic energy to heat polar molecules and moisture within the extraction system. Rapid internal heating can disrupt plant structures and accelerate release of compounds into the surrounding solvent. Potential advantages include shorter extraction times and reduced solvent consumption.
Comparative studies demonstrate that microwave-assisted and ultrasound-assisted technologies can both provide effective recovery of plant phenolics, although their relative performance depends on botanical material and process conditions.
The principal technical concern is again control. Rapid heating can be advantageous, but compounds sensitive to thermal exposure may require carefully controlled conditions. Microwave technology may also present different scale-up and equipment-design considerations from conventional stirred extraction or ultrasound processing.
Pressurised and Subcritical Water Extraction
Water changes its solvent properties as temperature and pressure increase. Under subcritical conditions, its polarity decreases, enabling water to solubilise compounds that are poorly extracted under conventional aqueous conditions.
This creates the possibility of expanding the chemical range of water based extraction while avoiding some organic solvents. However, higher temperatures also increase the potential for thermal degradation. Pressure rated equipment increases capital and operating complexity.
Subcritical water extraction therefore illustrates a recurring pattern in green technology: reducing one environmental burden can introduce a new engineering constraint. Technology selection must consequently consider the entire commercial process rather than solvent choice alone.
Supercritical Carbon Dioxide
Supercritical carbon dioxide extraction is well established for certain non-polar and moderately lipophilic botanical constituents. Carbon dioxide becomes supercritical above its critical temperature and pressure and can then exhibit useful solvent properties. Advantages include minimal conventional solvent residue and the ability to recover CO₂ following depressurisation. It can be particularly useful for volatile oils and lipophilic constituents.
Limitations include relatively high equipment cost, pressure requirements and limited extraction of strongly polar compounds unless modifiers or co-solvents are introduced.
Supercritical extraction is therefore highly valuable for some botanical targets but is not a universal replacement for liquid-solvent extraction.
Natural Deep Eutectic Solvents
Natural deep eutectic solvents and related systems have attracted growing interest as alternative extraction media. They can be created by combining naturally occurring compounds in proportions that generate liquids with solvent properties differing from those of the individual components.
Research has demonstrated their ability to extract phenolics and flavonoids from a range of plant matrices, including in combination with ultrasound-assisted extraction. Their potential is considerable. However, several issues remain important for commercial botanical ingredients: solvent viscosity; downstream removal; regulatory acceptance; residual solvent in finished ingredients; analytical interference; cost; toxicological characterisation; and performance at manufacturing scale.
A solvent can be described as natural without automatically being technically or regulatory appropriate for every application.
Enzyme Assisted Extraction
Plant cell walls contain structural polysaccharides that can limit access to intracellular compounds. Enzyme-assisted extraction uses enzymes capable of modifying these structures and facilitating compound release. Potential benefits include mild processing conditions and improved recovery.
However, enzyme cost, activity control, processing time, enzyme deactivation and downstream compatibility must be considered. The method may be particularly attractive where cell-wall degradation provides selective access to target constituents. Again, its value depends on the structure of the botanical material and the chemistry of the desired ingredient.
Hybrid Extraction Technologies
Future botanical manufacturing is unlikely to rely exclusively on isolated technologies. Combinations may offer greater process control.
Examples include: ultrasound combined with aqueous ethanol; ultrasound followed by membrane separation; ultrasound with pressurised extraction; microwave and ultrasound combinations; enzyme treatment followed by solvent extraction; green solvent systems combined with physical intensification; and extraction followed directly by selective purification.
Recent experimental research has investigated combined ultrasound and microwave technologies in medicinal plants including rosemary and oregano, demonstrating the continuing movement towards hybrid extraction systems.
Hybridisation can improve recovery. It can also increase process complexity. The important question is whether the additional technology provides a measurable benefit sufficient to justify that complexity.
Extraction Yield Is an Incomplete Performance Measure
Total extraction yield is frequently reported as a primary measure of process success. This can be misleading. Suppose Process A extracts 25% of the starting plant mass while Process B extracts 15%. Process A might initially appear superior. However, if the additional extracted material consists primarily of sugars, waxes, chlorophyll, protein or other compounds that subsequently require removal, the higher total yield may actually represent poorer selectivity.
For bioactive ingredient manufacturing, more useful performance measures may include: target-compound recovery; target concentration; selectivity; preservation of related phytochemicals; antioxidant or other relevant functional measures; degradation markers; impurity profile; solvent consumption; energy consumption; and downstream processing requirement. The objective is therefore not to extract the greatest possible quantity of plant matter. It is to recover the appropriate chemical fraction.
Extraction and Standardisation Are Interdependent
The previous papers in this series considered botanical standardisation and extract authenticity. Extraction technology directly influences both. If extraction selectively changes the ratios of naturally occurring compounds, then the chromatographic fingerprint of the extract will differ from that of the original plant. This is expected.
The critical requirement is understanding and controlling the relationship. European regulatory guidance on herbal medicinal products recognises that product quality depends not simply on final testing but on starting material, manufacturing development, process controls, validation and specifications throughout manufacture.
Extraction conditions therefore become part of botanical identity at the level of the finished preparation. Two extracts from the same plant should not automatically be treated as chemically equivalent if their extraction processes are materially different.
Downstream Concentration
Extraction is only the beginning of botanical ingredient manufacture. The resulting liquid may contain a relatively low concentration of dissolved solids and require solvent removal.
This creates another point of technical risk. Evaporation or distillation exposes the extract to combinations of: temperature; time; oxygen; changing concentration; changes in viscosity; and changing interactions between compounds.
Vacuum concentration can reduce boiling temperatures and thereby limit thermal exposure. However, lower bulk temperature does not eliminate oxidation or other degradation mechanisms. As solvent is removed, chemically sensitive compounds may become increasingly concentrated in an environment quite different from that in which they originally existed within the plant.
Green extraction must therefore be linked with green and chemically protective concentration technology.
Purification and Selectivity
Crude botanical extracts often contain more material than is required for a final commercial ingredient. Purification can increase target-compound concentration and remove undesirable components.
Potential approaches include membrane technologies, adsorption systems, chromatography, phase separation, precipitation and selective solvent processes.
Every purification stage changes the composition of the botanical preparation. Increasing purification may improve analytical potency but simultaneously reduce the chemical complexity characteristic of the original botanical extract.
European regulatory guidance recognises this issue and has specifically considered the point at which increasingly purified extracts may no longer represent conventional herbal preparations.
This creates both a scientific and a commercial question: At what point does a botanical extract become a purified chemical fraction rather than an extract in the conventional sense?
Solvent Recovery
Solvent choice has direct environmental and economic consequences. Where ethanol or other recoverable solvents are used at commercial scale, recovery can materially improve process economics and environmental performance. However, recovered solvent must remain suitable for its intended reuse.
Regulatory guidance for herbal medicinal preparations specifically addresses recovered and recycled solvents, reflecting the importance of solvent quality in pharmaceutical botanical manufacturing. Commercial green extraction should therefore consider not just: Which solvent is used? but: Can it be safely and efficiently recovered, characterised and reused?
From Laboratory to Manufacturing Scale
One of the greatest challenges facing advanced extraction technologies is scale-up. Laboratory equipment can provide excellent mixing, rapid heat transfer and high energy intensity in small volumes. Those conditions may not translate directly into larger manufacturing vessels.
Ultrasound provides a useful example. Energy distribution within a small laboratory vessel can differ substantially from energy distribution in an industrial tank. Probe geometry, vessel configuration, liquid depth, viscosity, solids loading and recirculation can all affect cavitation and mass transfer.
Consequently: successful laboratory extraction demonstrates technical potential, not automatic industrial scalability. Scale-up requires renewed experimentation.
Reproducibility Is as Important as Optimisation
The best-performing extraction condition in a laboratory trial is not necessarily the best commercial process. Commercial manufacturing requires repeatability. A slightly lower extraction yield achieved consistently across variable botanical raw materials may be commercially preferable to a theoretically higher yield that is sensitive to small changes in moisture, particle size or plant chemistry.
Process optimisation should therefore include: robustness; acceptable operating ranges; raw-material variability; equipment variation; analytical reproducibility; process control; and batch-to-batch consistency. This shifts the objective from finding a single “perfect” condition towards defining a robust processing space.
Green Does Not Mean Unregulated
The adoption of environmentally preferable technologies does not remove normal requirements relating to botanical ingredient quality. Extracts intended for regulated products may still require control of: botanical identity; extraction solvent; drug-extract ratio or equivalent manufacturing information; residual solvents; contaminants; microbiology; marker or active compounds; stability; and processing consistency.
The EMA’s quality and specifications framework makes clear that manufacturing and extraction form part of the overall quality-control strategy for herbal preparations. Environmental improvement must therefore operate within, rather than instead of, pharmaceutical and ingredient quality systems.
Agricultural Side Streams and Green Extraction
Green extraction also creates opportunities to recover valuable compounds from agricultural materials that might otherwise have limited economic value. Leaves, skins, pomace, seeds, husks and other processing residues can contain significant concentrations of polyphenols, pigments, oils and other phytochemicals.
The environmental argument is attractive:
agricultural residue → bioactive recovery → value-added ingredient
However, waste stream valorisation introduces its own quality requirements. A material produced as an agricultural residue was not necessarily grown, harvested or stored with pharmaceutical or nutraceutical extraction in mind. Contamination, degradation, variable storage conditions and supply-chain traceability therefore require careful evaluation. A low-cost botanical resource is useful only if it can become a consistent and safe raw material.
Designing Extraction Around the Target Compound
A more sophisticated approach to botanical extraction begins not with the extraction technology, but with the target chemistry.
The development pathway becomes:
Define the botanical material
→ Identify the target compound or chemical profile
→ Understand polarity and stability
→ Select compatible solvent systems
→ Evaluate extraction technologies
→ Measure recovery and degradation
→ Assess downstream concentration and purification
→ Evaluate stabilisation
→ Confirm reproducibility
→ Scale the complete process
This reverses a common development approach in which a technology is selected first and botanical materials are then processed through it.
The better question is not: What can this extraction machine extract? It is: What processing environment does this botanical chemistry require?
From Green Extraction to Green Manufacturing
The future of botanical processing will increasingly require a broader definition of sustainability. An extraction process cannot be evaluated independently from: botanical cultivation; transport; drying; milling; solvent production; extraction; solvent recovery; concentration; purification; encapsulation; drying; packaging; and waste treatment.
A low-temperature extraction that produces a highly dilute extract requiring enormous downstream evaporation may not deliver the environmental benefits initially assumed. Similarly, a process using a renewable solvent may be less sustainable if that solvent cannot practically be recovered or if it creates significant downstream waste. The future objective should therefore be green botanical manufacturing, not merely green extraction.
Commercial Implications
The increasing demand for botanical ingredients creates strong incentives to improve extraction efficiency. However, commercial advantage is unlikely to arise from adopting a particular technology simply because it is described as green.
Competitive botanical processes will instead combine several attributes: effective target-compound recovery, chemical integrity, reproducibility, low undesirable co-extraction, manageable solvent and energy requirements, downstream compatibility, scalability and stable final ingredients. This systems approach creates a higher technological threshold than conventional extraction optimisation. It also creates greater opportunity for innovation.
Future Research
Several areas warrant continued investigation. Improved understanding of the interactions between botanical matrices, solvent systems and physical extraction technologies could enable more predictive process design. Real-time and rapid analytical technologies may permit extraction processes to be controlled according to chemical composition rather than time alone. Chemometric models may help connect raw-material fingerprints with optimum processing conditions. Hybrid extraction and purification technologies may improve selectivity while reducing solvent and energy use. Emerging solvent systems may expand the range of compounds recoverable using environmentally preferable processes.
Perhaps most importantly, extraction research needs to move beyond isolated optimisation studies towards investigation of the complete manufacturing pathway. The important measure is not simply how much bioactive compound leaves the plant. It is how much chemically intact, commercially useful bioactive material remains in the final stable ingredient.
Conclusion
Green extraction represents an important evolution in botanical ingredient manufacturing. Water, aqueous ethanol, vegetable oils and emerging alternative solvents can reduce reliance on less desirable chemical systems. Ultrasound, microwaves, pressure, enzymes and other assisted technologies can accelerate mass transfer and improve extraction efficiency. None of these approaches is universally optimal.
Botanical extraction is governed by interactions between plant matrix, compound chemistry, solvent polarity, temperature, time, energy input, oxygen exposure and downstream processing. The appropriate extraction system must therefore be designed around the specific botanical material and target chemical profile.
This changes the central question from: “Which green extraction technology gives the highest yield?” to: “Which combination of botanical material, solvent, technology and processing conditions delivers the desired chemical profile with the greatest practical efficiency and least unnecessary environmental and chemical impact?” That question is more complex. It is also considerably more relevant to the development of the next generation of standardised botanical ingredients.
Research Context
Botanical Innovations is undertaking ongoing research into green extraction and purification of botanical bioactive compounds, including the interaction between botanical source, solvent systems, physical extraction technologies, concentration, purification, encapsulation and finished-ingredient stability.
This paper discusses published scientific principles and the broader technological challenges relevant to botanical extraction.
Selected Bibliography
European Medicines Agency. (2022). Guideline on quality of herbal medicinal products/traditional herbal medicinal products, Revision 3. EMA/HMPC/CHMP/CVMP/201116/2005 Rev. 3.
European Medicines Agency. (2022). Guideline on specifications: test procedures and acceptance criteria for herbal substances, herbal preparations and herbal medicinal products/traditional herbal medicinal products, Revision 3. EMA/HMPC/162241/2005 Rev. 3.
European Medicines Agency. Reflection paper on the use of recovered/recycled solvents in the manufacture of herbal preparations for use in herbal medicinal products/traditional herbal medicinal products.
European Medicines Agency. Reflection paper on the level of purification of extracts to be considered as herbal preparations.
Irakli, M. et al. (2023). Comparative investigation of ultrasound- and microwave-assisted extraction of phenolic compounds from sage. Published experimental research indexed in PubMed.
Yusoff, I.M. et al. (2022). A review of ultrasound-assisted extraction for plant bioactive compounds. Food Research International, 157, 111268.
Carreira-Casais, A. et al. (2021). Benefits and drawbacks of ultrasound-assisted extraction for the recovery of bioactive compounds from foods. Molecules, 26.
Wen, C. et al. (2018). Advances in ultrasound-assisted extraction of bioactive compounds from cash crops. Ultrasonics Sonochemistry, 48, 538–549.
Zhang, Y. et al. (2012). Degradation study of carnosic acid, carnosol, rosmarinic acid and rosemary extract assessed using HPLC. Journal of Agricultural and Food Chemistry, 60, 9305–9314.
Additional primary literature covering aqueous and ethanolic extraction, ultrasound, microwave, supercritical-fluid extraction, subcritical water, enzyme-assisted extraction and emerging solvent systems should be incorporated during final reference verification.