Review
Green Technology for Extraction of Bioactive Compounds from Edible Plants
2024 Volume 73 Issue 10 Pages 1249-1265
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2024 Volume 73 Issue 10 Pages 1249-1265
In modern society, the use of bioactive compounds in various foods and cosmetic industry sectors through the development of general foods, functional foods, cosmetics, customized cosmetics and several pharmaceuticals has become one of the key technological sources. The most critical step in isolating and purifying bioactive compounds from natural plant materials is the extraction process. Over the past five years, there has been a reasonable compromise between economic, social, and environmental requirements, resulting in safer and more efficient traditional and non-traditional extraction methods. This literature review aims to comprehensively review green extraction technologies for the extraction of bioactive compounds from plant materials from 2020 to 2024.
Green extraction technologies have become increasingly important in recent years, particularly in the food, pharmaceutical and cosmetics industries, where there is a growing demand for natural products produced in a sustainable and environmentally responsible way1). Due to the high complexity of extraction techniques and the increasingly demanding requirements of food safety authorities, current sample preparation and processes for the separation and extraction of bioactive compounds and contaminants from products are constantly being improved2). Extraction and processing of natural products can have negative impacts on the environment. Therefore, it is essential to implement sustainable extraction practices that minimize environmental damage while preserving the quality and quantity of extracted products. The use of sustainable green technologies is essential to promote economic growth and conserve biodiversity of bioactive single substances beneficial to humans3).
The qualitative and quantitative study of bioactive compounds in plant materials mostly involves appropriate extraction process methods, matrix properties, solvents, temperature, pressure, and time. Incorporating these extracted bioactive phenols into foods, cosmetics, and other value-added products requires efficient extraction strategies. To this end, several methods based on plant matrices have been optimized for the extraction of phenols and related compounds by various researchers. Extraction techniques are categorized into traditional and non-traditional extraction techniques4). Traditional extraction techniques for bioactive compounds include solvent extraction, steam distillation, among others, with various research studies applied5),6),7),8),9). Recently, in addition to traditional techniques, non-traditional techniques are combined with other technologies and applied as green technologies10), 11). These traditional and non-traditional extraction techniques each have their own advantages and are selected and applied accordingly. This literature review paper aims to comprehensively review green extraction technologies for the extraction of bioactive compounds from plant materials from 2020 to 2024.
Typical bioactive compounds in plant materials are produced as secondary metabolites through various biological pathways of secondary metabolism and play a pivotal role in protecting plants from biotic and abiotic stresses. The creation of new bioactive substances can be derived from natural products such as plants and animals, extracted and purified from microbial and plant/animal cell cultures, and they can also be synthesized chemically12), 13). The classification of bioactive compounds depends on specific purposes14). They can be categorized into several major chemical groups based on chemical classes and biochemical pathways, including glycosides (cardiac glycosides, cyanogenic glycosides, glucosinolates, saponins, and anthraquinone glycosides) , phenolic compounds (phenolic acids, hydroxycinnamic acids, stilbenes, flavonoids, and anthocyanins) , tannins (which are of two different types: condensed tannins, which are large polymers of flavonoids, and hydrolyzable tannins, which are polymers composed of a monosaccharide core attached to several catechin derivatives) , monoterpenoids, diterpenoids, sesquiterpenoids, phenylpropanoids, lignans, resins, alkaloids, furocoumarins, and naphthodianthrones, as well as proteins and peptides15). Terpenes are widely distributed in nature and are the primary constituents of essential oils, representing a significant class of bioactive compounds found in plant materials. Also known as isoprenoids, terpenes are a diverse group of naturally occurring plant chemicals. Although terpenes and terpenoids are often used interchangeably, they have slight chemical differences. Terpenes are volatile unsaturated hydrocarbons composed of isoprene monomer units forming five-carbon rings, while terpenoids are modified terpenes with different functional groups at various positions16). Terpenes are mainly classified based on the number and arrangement of these isoprene units into monoterpenes (C10) , sesquiterpenes (C15) , diterpenes (C20) , sesterterpenes (C25) , triterpenes (C30) , and tetraterpenes (C40) 17). The classification of terpene compounds, which belong to the group of plant chemicals among bioactive compounds, is shown in Fig. 1. Over the past decade, several extensive reviews of the biochemistry and genetics of plant terpenes have been conducted18). Monoterpenes (containing 10 carbon skeletons) are condensation products of two isoprene units, sesquiterpenes (C15) of three isoprene units, and diterpenes (C20) of four isoprene units. The actual condensation of these isoprene units in plants occurs in the diphosphate-activated form known as prenyl diphosphate. This condensation can proceed via two mechanisms: head-to-tail condensation resulting in trans-prenyl diphosphate and cis-prenyl diphosphate. Most plant triterpenes (e.g., sterols, C30) are produced through a one-to-one condensation of two trans-sesquiterpenyl diphosphate molecules, while most plant tetraterpenes (e.g., carotenoids, C40) are produced through the same one-to-one condensation of two trans-diterpenyl diphosphate molecules19).
Classification of terpene compounds.
The extraction process is the most crucial initial step in isolating and purifying bioactive compounds from plant materials. Extraction is a method for recovering specific components from a solution or solid mixture and is indispensable for sample pretreatment, experimental research, and qualitative analysis of bioactive compounds20). Plant bioactive compounds serve as essential sources for the development of foods, functional foods, cosmetics, pharmaceuticals, and various industries21). Generally, the extraction and isolation of bioactive compounds from natural resources follow established procedures: (1) thorough extraction (including immersion, steam hydrodistillation, expression, decoction, infusion, maceration, and Soxhlet extraction) , and (2) further chemical processing of the extracts to isolate the target compounds in pure form. Despite high energy consumption and large solvent volumes, traditional extraction methods often result in very low yields22). Therefore, over the past few decades, safer and more efficient extraction technologies have been considered based on a reasonable compromise between economic, social, and environmental requirements. Techniques aimed at reducing operating time, decreasing organic solvent consumption, and increasing extraction efficiency have been continuously developed. The amount of bioactive natural products extracted from natural resources is relatively low and exists within the plant matrix23). All plant components, such as the whole plant, leaves, roots, bark, tubers, wood, gums or oleoresins, exudates, fruits, figs, flowers, rhizomes, berries, and twigs, etc., produce active chemical substances in varying small amounts. Consequently, selecting the correct extraction process to maximize extract yield from the specific tissue is vital24), 25). The extraction and isolation of bioactive compounds from natural resources are classified into traditional and non-traditional extraction techniques, each with its own advantages26).
3.1 NADES (natural deep eutectic solvents)Natural deep eutectic solvents (NADES) possess unique physicochemical properties and several distinctive characteristics. Some of these characteristics include high solubility, low volatility, low toxicity, and tunability27). Additionally, NADES can dissolve a wide range of compounds, such as proteins, lipids, organic pollutants, metal ions, nucleic acids, and bismuth oxide nanoparticles that are insoluble in water28), 29). NADES are typically prepared by mixing natural hydrogen bond donors (HBD) and acceptors hydrogen bond acceptors (HBA) in different molar ratios at sub-ambient temperatures, applying stirring and heating. As suggested by the term ‘eutectic', the mixture of HBA and HBD results in a depression of the melting point of NADES compared to the individual components, allowing the mixture to remain in a liquid state at ambient temperature30). NADES with various molar compositions offer strong solubilizing abilities for diverse structural matrices and plant metabolites, enhancing the diffusion process through plant cell walls during auxiliary extraction31). According to the literature, these NADES can improve extraction yields and be used for targeted separation of specific types of metabolites32). The techniques for manufacturing NADES include thermal mixing, vacuum evaporation, ultrasound-based methods, and microwave-based methods, allowing the technology to be applied as needed. The thermal mixing method involves heating two components and stirring with or without a small amount of water to obtain a clear liquid33),34),35),36). Vacuum evaporation involves heating the NADES components under reduced pressure to remove excess water36). Ultrasound-based methods use ultrasonic waves to create cavitation, promoting the formation of NADES37). Microwave-based methods use microwave energy to induce molecular agitation and collisions between the components38). The progression of NADES extraction technology begins with preparing the natural compounds to be used in the experiments in appropriate ratios. The prepared NADES is then mixed with the samples in suitable proportions. The mixture is subjected to agitation or treatments such as ultrasonication for a specified duration and temperature to facilitate the dissolution of the target compounds. Following this, extraction conditions are optimized to achieve maximum efficiency. Post-extraction, centrifugation or filtration processes are employed to separate the solids from the liquids. The obtained extracts are then further purified or concentrated as needed based on the conditions. The extracted components are analyzed to evaluate extraction efficiency and concentration of the compounds, using various analytical techniques such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) . This process ensures that NADES performs the necessary extractions effectively. The procedural steps related to NADES extraction technology are illustrated in Fig. 239), 40).
Natural deep eutectic solvents.
Microwave-assisted extraction (MAE) has been considered a potential alternative to traditional solid-liquid extraction for extracting metabolites from plants41). MAE is one of the efficient extraction techniques based on microwaves generated by electromagnetic fields to extract oils from oilseeds, food, and plant materials44), 107). In this process, microwave energy heats the polar solvent in contact with the solid sample, increasing internal pressure and promoting cell wall rupture, thereby releasing bioactive compounds into the solvent42), 43). Utilizing the microwave effect, micropores are formed, disrupting the cell structure of the raw material, causing the cell contents to flow out and dissolve in the extraction solvent. After the extraction step, information regarding the phenolic composition characteristics of the extract is obtained44). Additionally, some research suggest that MAE is effective and can be combined with other extraction methods in oil production44), 45).
Considering economic and practical aspects, MAE is a powerful extraction technique for extracting phytochemicals, offering the benefit of enhanced recovery rates of active ingredients from samples with consistent reproducibility46), 105). The progression of MAE technology begins with preparing plant materials or substances of appropriate size for extraction. The next step involves determining the suitable solvent (such as water, ethanol, methanol, or acetone) and its ratio for the target material. The prepared solvent and sample are then combined and placed in a microwave extraction device, where parameters such as power output, temperature, and duration are set. The application of microwave energy heats the solvent, causing cell wall disruption, which enhances extraction efficiency. Upon completion of the extraction, the extract is cooled to room temperature, followed by filtration to remove solid residues and obtain the extract solution. The extract solution is then concentrated or further purified as necessary. The extracted components are analyzed to assess extraction efficiency and compound concentration using various analytical techniques such as HPLC and GC-MS. The procedural steps related to MAE extraction technology are illustrated in Fig. 347), 48).
Microwave-assisted extraction.
Ultrasound-assisted extraction (UAE) is one of the eco-friendly extraction technologies. Essentially, ultrasonic devices generate sound waves with frequencies ranging from 20 kHz to 100 kHz, which exceed the hearing capacity of humans49). By using high-intensity ultrasonic waves, cavitation bubbles are created, disrupting the cell structure of the raw material, increasing the permeability of cell walls, enhancing the mass transfer rate of the extractant, and accelerating the dissolution of the extractant and target compounds into the cells of the raw material50). The extraction mechanism by ultrasound involves two main types of physical phenomena: diffusion across the cell wall and washing out the cell contents after the wall is broken51). UAE is influenced by crucial factors such as the moisture content of the sample, particle size, solvent, temperature, pressure, frequency, and ultrasonic treatment time, all of which play significant roles in achieving efficient and effective extraction. Additionally, UAE can be integrated with various conventional techniques to enhance the efficiency of existing systems52). The primary advantage of UAE can be observed in solid plant samples, where ultrasonic energy promotes the leaching of organic and inorganic compounds from the plant matrix53).
Moreover, the advantages of this extraction technique include reduced extraction time, energy, and solvent usage. Ultrasonic energy for extraction also facilitates more effective mixing, faster energy transfer, reduced thermal gradients and extraction temperatures, selective extraction, reduced equipment size, quicker response for process extraction control, rapid initiation, increased production, and the elimination of process steps54). Process optimization is a crucial step to achieve maximum extraction efficiency of compounds. MAE provides rapid energy transfer and simultaneous heating of the biological material and solvent assembly and has been employed in recent years as a strategy to improve the recovery of bioactive natural products55). The progression of UAE technology begins with preparing plant materials of uniform size. Next, the solvent suitable for the target material (such as water, ethanol, methanol, or acetone) and the solvent-to-material ratio are determined. The prepared solvent and plant materials are then mixed and subjected to ultrasound using either an ultrasonic probe or bath, with parameters such as ultrasonic power, frequency, temperature, and duration set accordingly. During this process, cavitation bubbles form in the solvent due to the ultrasound, and their collapse generates strong shear forces that disrupt cell walls, facilitating the release of intracellular compounds into the solvent. After ultrasonic treatment, the mixture is filtered to separate the solid plant materials from the solvent containing the extracted compounds. If necessary, additional purification steps such as liquid-liquid extraction or chromatography can be employed. The extracted components are then analyzed to determine their concentration and purity using various analytical techniques such as HPLC, GC-MS, and spectrophotometry. The procedural steps related to UAE extraction technology are illustrated in Fig. 456), 57).
Ultrasound-assisted extraction.
Natural eutectic organic solvent-green refining (NEOS-GR) is based on the microwave hydrodiffusion & gravity technique, a novel and eco-friendly method for extracting essential oils from various types of aromatic plants. This green extraction technology employs an innovative inverted microwave alembic that combines microwave heating at atmospheric pressure with gravity. The method, based on a relatively simple principle, involves placing plant material in a microwave reactor without adding solvents or water. A physical phenomenon known as hydrodiffusion allows the extract (comprising water and essential oil) to diffuse out of the plant material and drop from the microwave reactor under the influence of gravity, pass through a perforated Pyrex disc. An external cooling system continuously cools the extract outside the microwave. The water and essential oils are collected and separated in a vessel traditionally known as a Florentine flask. It is noteworthy that this eco-friendly method can extract essential oils without the distillation and evaporation processes, which are the most energy-intensive operations between unit processes58), 59).
3.5 SFE (supercritical fluid extraction)Supercritical fluid extraction (SFE) is one of the eco-friendly extraction technologies that offers numerous advantages over conventional extraction processes. Enhanced selectivity, higher extraction yields, better fractionation capabilities, and lower environmental impact have been critical to the significant growth of SFE60), 108). The application of SFE is advantageous for processing high-yield quality products61), 106). This technique utilizes the unique properties of supercritical fluids to extract samples. A supercritical fluid exhibits the ability to diffuse through materials like a gas while dissolving substances like a liquid. Supercritical carbon dioxide is predominantly used due to its low viscosity, high diffusivity, and high volatility, making it an ideal solvent. Additionally, its low critical temperature makes it easily applicable to thermally unstable compounds. By controlling temperature and pressure conditions that determine density and solvent strength, SFE is an efficient and selective technique for obtaining high-quality extracts62), 109). However, due to its non-polar nature, it is inefficient for extracting polar solutes. To address this, volatile polar modifiers such as methyl acetate, diethyl ether, methanol, or formic acid can be added63). SFE is a crucial technique today from both economic and ecological perspectives, used to extract a variety analyte from diverse matrices such as soil contaminants, fats in foods, bioactive compounds in plants, and additives in polymers64), 65). The progression of SFE technology begins with drying and grinding the materials to be extracted into a uniform size. The prepared samples are then loaded into an extraction vessel, which is securely sealed to withstand high pressure. In this process, CO2 is pumped through a heat exchanger where it is heated above its critical temperature and pressurized above its critical pressure to become a supercritical fluid. The supercritical CO2 is introduced into the extraction vessel containing the sample, where optimized extraction parameters are set to dissolve the target compounds. The supercritical CO2 carrying the dissolved compounds exits the extraction vessel and enters a separator where the pressure is reduced, causing the CO2 to revert to a gaseous state and separate from the extracted compounds. The extracted compounds are collected, and the CO2 can be recycled back into the system. Depending on the application, the extracted material may undergo further purification steps. Various analyses, such as HPLC, GC-MS and spectrophotometry, are conducted to determine the composition of the extract.
The procedural steps related to SFE technology are illustrated in Fig. 5. While CO2 is the most commonly used supercritical fluid, other supercritical fluids like propane, ethane, or water (for some advanced applications) can be used depending on the specific requirements of the extraction process. Figure 5 illustrates that not only CO2 but also other suitable supercritical fluids can be flexibly chosen based on the characteristics of the target compounds and the matrix66), 67).
Supercritical fluid extraction.
Supercritical carbon dioxide (CO2) extraction (SCDE) is an innovative extraction technology. As the extraction solvent is supercritical CO2, it is considered a 〝clean process〟 for environmental protection68). This method has emerged as an alternative process to maximize both the selectivity and yield of reactions by rapidly separating highly reactive products from the reaction mixture69). Additionally, the extracted products can be conveniently and selectively separated from the supercritical fluid by slightly adjusting the temperature or pressure. Given its supercritical state (Tc=31.1°C and Pc=7.4 MPa) , CO2, which is produced globally from fossil fuel combustion, offers the advantages of being a ‘green' solvent (neutral, non-toxic, and non-flammable) 70). The extraction method follows the same procedure as 3.5 SFE. However, a key difference from SFE is that it employs carbon dioxide as the supercritical fluid exclusively, making it a single-solvent specific type of SFE suitable for non-polar to moderately polar compounds. Additionally, the solvent power can be enhanced by adding co-solvents such as ethanol or methanol to extract more polar substances. The procedural steps of SCDE are illustrated in Fig. 671),72),73). Therefore, it is one of the most frequently used processes in chemical extraction70).
Supercritical carbon dioxide extraction.
Ultrasonic pulsed extraction (UPE) is recognized as an efficient and environmentally friendly extraction method across various fields74). This is a technique that uses high-frequency ultrasound to treat the solvent and samples, maximizing extraction efficiency by promoting cell wall destruction and solute diffusion. The repetitive on-off mode of ultrasonic operation moderately releases heat and reduces the degradation of bioactive compounds. Additionally, it facilitates particle size reduction, cell wall rupture, and enhanced mass transfer. Consequently, UPE is highly beneficial for bioactive extraction processes due to its higher product yield, scalability, minimal equipment requirements, low maintenance costs, and shorter processing times compared to other non-traditional techniques75), 76). Furthermore, it has been demonstrated to be a convenient, rapid, and economically viable method for extracting heat-sensitive bioactive compounds compared to several other technologies77). Studies have shown a preference for this technology due to its ability to achieve higher yields of bioactive components78). The progression of UPE begins with preparing the extraction materials by drying and sizing them uniformly. An optimal solvent-to-material ratio is then selected based on the target compounds. The ultrasonic pulse system is set up to apply mechanical vibrations (ultrasound) . The prepared plant materials are mixed with the chosen solvent in the extraction vessel. The mixture undergoes ultrasonic pulsed treatment (adjusting pulse duration, interval, cavitation, and optimizing parameters) . After the treatment, the mixture is filtered to separate the solid plant materials from the solvent containing the extracted compounds. The filtrate is then concentrated using methods such as rotary evaporation, followed by additional purification steps to isolate specific compounds. Various analyses, such as HPLC, GC-MS, and spectrophotometry, are performed to determine the concentration and purity of the extracts. The procedural steps related to UPE extraction technology are illustrated in Fig. 756),79).
Ultrasonic pulsed extraction.
Subcritical water extraction (SWE) is an advanced system for extracting plant metabolites, garnering significant interest from researchers due to its eco-friendly and safe solvent properties, which align with the sustainable management and efficient use of natural resources80). This process used water at temperatures between 100°C and 374.15°C and at pressures high enough to maintain the liquid state81). The main parameters involved in SWE are temperature, pressure, and time, while other external factors such as sample mean particle size, flow direction, solvent flow rate, cell shape, and additive mixtures also significantly impact the process depending on the solute characteristics82), 83). Considering the pros and cons of various green solvents, there is no perfect solvent for all applications; however, water stands out as the most environmentally friendly option. Compared to organic solvents, SWE offers enhanced efficiency, higher quality of extracts in a shorter time, better solubility, and is non-toxic, non-flammable, and easy to handle84),85),86). This technique is utilized for extracting bioactive compounds from soil, environmental samples, microalgae, and plant materials, as well as for purification and food safety analysis84). The progression of SWE begins with preparing the extraction materials by drying and sizing them uniformly. Optimal extraction parameters, including temperature, pressure, and the solvent-to-sample ratio, are selected based on the target compounds and their matrices. The SWE system (comprising heating, cooling systems, high-pressure pump, and extraction vessel) is set up, and water is pumped into the extraction vessel, heated to the desired temperature below its critical point. The prepared sample is then loaded into the extraction vessel, which is sealed to maintain the set high pressure during the extraction process. Subcritical water is introduced into the extraction vessel containing the sample, and optimized parameters are applied to dissolve and diffuse the compounds. The extract containing the dissolved compounds exits the vessel, passes through the cooling system, where the temperature and pressure are reduced, and is collected separately. The collected extract may undergo further purification steps such as filtration, centrifugation, or chromatography to isolate specific compounds. Various analyses, including HPLC, GC-MS, and spectrophotometry, are conducted to determine the composition and concentration of the extracted components. The procedural steps related to SWE extraction technology are illustrated in Fig. 887),88),89).
Subcritical water extraction.
This review paper provides a comprehensive review of research data on green technologies used for extracting bioactive compounds from edible plants, focusing on optimal conditions from 2020 to 2024. This review is visually summarized in Fig. 9 for schematic representation of green extraction technologies of bioactive compounds through natural product chemistry approaches.
Non-traditional and traditional extraction techniques select appropriate technology fusion, materials, solvents, and conditions for more efficient extraction. Table 1 summarizes the optimal extraction conditions set in studies from 2020 to 2024 on extraction technology applications for plant materials, along with the resulting physiological benefits for humans and the extracted components.
Schematic representation of green extraction technologies of bioactive compounds through natural product chemistry approaches.
An extraction experiment using NADES-8 (L-proline, and lactic acid) applied to Michelia alba (Malba) set the optimal conditions as ultrasound time (17.98 minutes) , Moisture content (48.52%) , and Solid: solvent ratio (59.79 g/mL) . This resulted in the extraction of phenolic compounds (cinnamic acid, rutin, cyanidin, catechol, caffeic acid, geraldol, coumaric acid, and ferulic acid) that showed specific physiological benefits for humans. These compounds effectively removed reactive oxygen species generated in inflammatory cells, reducing oxidative stress caused by inflammation, as shown in Table 190). In an extraction experiment fusing NADES with the MAE technique, the application to date palm leaves set the optimal conditions as NADES dilution (49%) , Treatment time (0.84 minutes) , and Investigation power (800 W of MW) . This resulted in the extraction of polyphenols (gallic acid, 1,2-dihydroxy benzoic acid, catechin, 4-hydroxy benzoic acid, vanillic acid, syringic acid, coumaric acid, ferulic acid, rutin hydrate, and cinnamic acid) that showed specific physiological benefits for humans. The extraction method's effectiveness on the biological activity of polyphenols demonstrated the inhibition of various markers involved in oxidative stress, diabetes, and hypercholesterolemia metabolic disorders, as shown in Table 191). An extraction experiment using UAE applied to green coconut shell set the optimal conditions as ultrasonication treatment time (15 minutes) , temperature (33°C) , and solid: solvent ratio (24 w/v) . This resulted in the extraction of phenols, flavonoids, tannins, and antioxidants that showed specific physiological benefits for humans. The method maximized the extraction of antioxidants and antimicrobial activities from plant waste, as shown in Table 192). An extraction experiment using NEOS-GR applied to Citrus limon leaves set the optimal conditions as extraction time (50 minutes) , temperature (10°C) , and investigation power (700 watts for 25 minutes) . This resulted in the extraction of limonene, geranial, citronellic acid, neryl acetate, and geranyl acetate that showed specific physiological benefits for humans. The bioactive compounds from plants exceeded standard antioxidants, effectively scavenged reactive oxygen species, alleviated oxidative stress, and exhibited strong antimicrobial activity against various pathogens, as shown in Table 193). An extraction experiment using UAE applied to papaya leaves set the optimal conditions as solid: solvent ratio (0.2 g/mL) , temperature (70°C) , and ultrasonication treatment time (20 minutes) . This resulted in the extraction of papain, chymopapain, cystatin, tocopherol, ascorbic acid, flavonoids, cyanogenic glucosides, and glucosinolates that showed specific physiological benefits for humans. The bioactive compounds from plants demonstrated effectiveness in alleviating menstrual discomfort and reducing nausea, as shown in Table 194). An extraction experiment using SFE applied to clove leaves set the optimal conditions as pressure (200 bar) , temperature (400°C) , and Yield (0.81) g extract/g CO2 (0.0012) . This resulted in the extraction of eugenol, β-caryophyllene, α-humulene, and eugenyl acetate, which showed specific physiological benefits for humans. These bioactive compounds from plants demonstrated maximized antibacterial, anti-inflammatory, and antioxidant capacities, as shown in Table 195).
Moreover, an extraction experiment using SCDE applied to blueberry pomace set the optimal conditions as extraction temperature (40°C) , pressure (34.7 MPa) , and CO2 flow rate. This resulted in the extraction of anthocyanins, namely, cyanidin, petunidin, peonidin, pelargonidin, delphinidin, and malvidin, which showed specific physiological benefits for humans. These compounds significantly reduced oxidative stress and exhibited various inherent functions (antioxidant activity, antidiabetic activity, anti-obesity activity, antimicrobial activity, anticancer effects, cardioprotective effects, hepatoprotective effects, and neuroprotective effects) when integrated into different systems, as shown in Table 196). An extraction experiment using UPE applied to Mulberry (Anthocyanins) set the optimal conditions as solid: solvent ratio 1:15 (w/v) , Extraction time 60 min, and Extraction temperature 40°C. This resulted in the extraction of C3G, ascorbic acid (Vc) , PNP, α-glucosidase, α-amylase, and DPPH, which showed specific physiological benefits for humans. These compounds exhibited hypoglycemic activity and could be used in the development of functional foods for the prevention and treatment of diabetes and its complications, as shown in Table 197). An extraction experiment using EAE-HHP applied to grape pomace (skin, seeds, and stalks) set the optimal conditions as pressure (50 MPa) and time (10 minutes) . This resulted in the extraction of antioxidant capacity, which showed specific physiological benefits for humans. The study demonstrated that treatment using HHP is more efficient compared to EAE and that the combination of these technologies maximizes the prevention of various diseases induced by oxidative stress and diabetes. Additionally, it was shown to prevent postprandial hyperglycemia by forming complexes with digestive enzymes, thus maximizing diabetes prevention, as shown in Table 198). An extraction experiment using SWE applied to coriander (Coriandrum sativum L.) seeds set the optimal conditions as Extraction temperature (110-170°C) and Extraction time (5-10 minutes) . This resulted in the extraction of monoterpenes (linalool, linalool oxide, camphor, and geraniol) , which showed specific physiological benefits for humans. These compounds demonstrated anxiolytic effects and revealed the potential of linalool oxide as an anticonvulsant in psychopharmacological studies, as shown in Table 199). Also, Table 2 summarizes the optimal extraction conditions and resulting advantages of recent technological advancements for each extraction technique, based on studies conducted between 2020 and 2024.
Case studies of extraction techniques.
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The extraction experiments using MAE applied to Aloe barbadensis Miller were conducted under optimal conditions set at 3 minutes, 500 W, 40% ethanol, 1:20 g/mL, and 70°C. The main finding, which is listed in Table 2, indicated that prolonged exposure times exceeding 3 minutes can lead to sample overheating, resulting in decreased extraction efficiency and yield recovery. Higher microwave power induces the degradation of biocompounds. In MAE, diluted ethanol is more efficient due to the high dielectric properties of water. Under optimized conditions, LC-QTOF-MS results of Aloe vera leaf extract revealed a total of 32 phenolic compounds and 29 saponin compounds, including phenols, triterpenoids, and steroidal saponins100).
The extraction experiments using HAE, UAE, and MAE were conducted on the leaves of the Malva Nut Tree (Scaphium macropodum) , each under their optimal conditions. HAE was set at water at 100°C, methanol at 64°C, and methanol at 78°C for 30 minutes. UAE was conducted for 30 minutes at 50 W and 40 kHz. MAE was performed for 30 seconds at 450 W. The highest extraction yield was obtained using the HAE method with water solvent (4.87±0.21%) , while the lowest yield (2.16±0.24%) was obtained using the MAE method with ethanol solvent. It is clearly confirmed that the suitable solvent for achieving optimal extraction yield varies depending on the plant species. This main finding is listed in Table 2101).
The extraction experiments using MAE applied to GP were optimized with conditions set to an ethanol concentration of 20-60% and a temperature range of 100-160°C. The application of NADES has demonstrated excellent results in enhancing phenol yields and extracting bioactive compounds. However, high viscosity remains a challenge for pressurized liquid extraction (PLE) . Increasing the temperature can help adjust this parameter; nevertheless, some drawbacks, such as anthocyanin loss and undesirable reactions, have been observed at temperatures above 100°C. Novel PLE techniques, such as accelerated solvent extraction, significantly reduce extraction time and increase the release of target phenolics, as illustrated in Table 2102). The extraction experiments using NADES applied to William banana flower stalk fiber were optimized with conditions set to extraction times of 10 minutes, 20 minutes, and 30 minutes; ultrasound amplitudes of 70%, 80%, and 90%; NADES concentrations of 30%, 50%, and 70%; and solid-to-solvent ratios of 1:30, 1.5:30, and 2:30 g/mL. Among the seven NADES tested, ChCl-LA exhibited the highest extraction efficiency for recovering bioactive compounds and the highest antioxidant activity, as illustrated in Table 2103).
The extraction experiments using MAE and UAE on Pomelo (Citrus maxima) peel were optimized under specific conditions: MAE with a maximum power output of 850 W, an operating frequency of 2450 MHz, and a temperature of 40°C; UAE with a 100 W, 20 kHz ultrasonic processor, a 5.00 mm probe, 30 minutes of ultrasonic treatment time, and a temperature of 70°C. The MAE method generated the highest yield with the lowest Degree of Esterification DE value. All extracted pectins were classified as HMP, with the presence of highly pure pectic acid (homogalacturonan) . However, noticeable changes in the physical structure of pectin were not confirmed. The fact that pectin can be commercially extracted from pomelo peel using MAE technology enhances its economic attractiveness, as illustrated in Table 2104).
Recent novel studies of extraction techniques.
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As energy costs rise and the green era dawns, the essential oil extraction industry is focusing on developing new extraction processes. The chemical and biological characterization of aromatic compounds and products obtained through clean technologies from plant materials significantly influences the development of food, functional foods, pharmaceuticals, cosmetics, and perfumes. However, there is a lack of sufficient research data on processes that do not diminish the inherent functions of natural extracts among existing extraction technologies. This comprehensive review aims to scale up green extraction technologies to an industrial level by designing extraction processes that ensure the stabilization and preservation of aromatic compounds, emphasizing the acquisition of stable, bioactive, and soluble single compounds using green extraction techniques. This transition involves addressing issues related to equipment design, cost efficiency, and maintaining product quality during large-scale production. The choice and optimization of extraction techniques also affect the measurement of extraction efficiency. Therefore, establishing standardized protocols and regulatory frameworks for eco-friendly extraction technologies can ensure product safety, quality, and consistency, and promote the widespread adoption of sustainable practices in the industry. Additionally, the development of hybrid extraction technologies that integrate traditional methods with modern green techniques can maximize efficiency and minimize the degradation of sensitive compounds by leveraging the strengths of various technologies. Applying computer modeling and process simulation enables precise control of extraction parameters such as temperature, pressure, solvent composition, and extraction time, leading to more consistent product quality and improved extraction efficiency. These advancements are expected to increase the utilization of renewable solvents and continue the innovation of efficient energy extraction technologies, thereby reducing energy consumption and shortening extraction times to make them more suitable for industrial applications. Collaboration among chemists, biologists, engineers, and industry stakeholders is crucial for the development of cutting-edge extraction technologies and promoting interdisciplinary research initiatives that drive innovation across various sectors. Integrating these advancements will revolutionize extraction processes, enhancing efficiency and quality while contributing to environmental sustainability and the development of high-value products for diverse applications. Further research is needed to streamline the extraction methods of these bioactive compounds and handle them more effectively.
