Supercritical Fluid Extraction Using CO2: Main Applications and Future Perspectives

Optimization and evaluation of a simplified green biorefinery for alginate extraction from sugar kelp (Saccharina latissima)

A simplified two-stage ultrasound-assisted biorefinery process for sodium alginate extraction from sugar kelp (Saccharina latissima) was developed using green solvents. The process yielded three distinct fractions: fucoidan/laminarin (S1), sodium alginate (S2), and cellulose (P2). The results were analyzed with response surface methodology. Key parameters, including sonication amplitude, time, and pH, were evaluated, and sonication energy was introduced as a predictive factor to improve model accuracy. Mathematical optimization of the response surface model identified an optimal sodium alginate yield of 76.4 % at pH 2 and 432.2 kJ of sonication energy. Fourier-transform infrared spectroscopy (FTIR) confirmed effective sodium alginate fractionation, and molecular weight analysis correlated viscosity with alginate quality. Inductively coupled plasma mass spectrometry (ICP-MS) showed reduced heavy metal content in both fucoidan/laminarin and alginate, indicating an improved safety profile for potential food and nutritional applications. This scalable and eco-friendly biorefinery highlights an environmentally sustainable approach for sodium alginate production, maximizing biomass valorization and ensuring product safety.

Nutraceutical potential of Mediterranean agri-food waste and wild plants: Green extraction and bioactive characterization

The agricultural waste and wild plants of the Mediterranean region offer significant nutraceutical potential, rich in bioactive compounds such as phenolics, carotenoids, lipids and volatile organic compounds. These compounds exhibit health-promoting properties, including antioxidant, neuroprotective and anti-inflammatory effects. Advanced analytical techniques such as HPLC, GC-MS and NMR are essential for the accurate chemical characterization of these bioactives. Green extraction methods, including ultrasound-assisted, enzyme-assisted and cold plasma-assisted extractions, provide efficient and environmentally friendly alternatives to classical techniques for the isolation of bioactive compounds. The valorization of Mediterranean agricultural by-products, such as olive pomace, grape seeds, and citrus peels, exemplifies sustainable approaches to the utilization of these underutilized resources. This chapter explores the bioactive characterization and green extraction methods that contribute to unlocking the nutraceutical potential of Mediterranean plant waste and wild plants, highlighting their role in the development of functional foods and natural health products.

Extraction of Bioactive Compounds from Wine Lees: A Systematic and Bibliometric Review

The extraction of bioactive compounds from wine lees involves a variety of methods, the selection of which is crucial to ensure optimal yields. This systematic review, following PRISMA guidelines and utilizing the Web of Science database, aimed to examine the current state of this field, providing insights for future investigations. The search employed strategies with truncation techniques and Boolean operators, followed by a three-step screening using well-defined eligibility criteria. A bibliometric analysis was conducted to identify authors, affiliations, countries/regions, and research trends. Thirty references were selected for analysis, with Spain standing out as the main source of research on the topic. The majority of studies (66%) focused on the extraction of bioactive compounds from alcoholic fermentation lees, while 33% were directed towards malolactic fermentation lees. Binary mixtures (ethanol-water) were the predominant solvents, with ultrasound being the most used extraction method (31.3%), providing the highest average yields (288.6%) for the various evaluated compounds, especially flavonoids. The potential of wine lees as a source of bioactive compounds is highlighted, along with the need for further research exploring alternative extraction technologies and the combination of methods. Additionally, the importance of "in vitro" and "in vivo" tests to assess the bioactive potential of lees, as well as the use of computational tools to optimize extraction and identify the molecules responsible for bioactive activity, is emphasized.

Supercritical Carbon Dioxide Extraction of Coumarins from the Aerial Parts of Pterocaulon polystachyum

Pterocaulon polystachyum is a species of pharmacological interest for providing volatile and non-volatile extracts with antifungal and amebicidal properties. The biological activities of non-volatile extracts may be related to the presence of coumarins, a promising group of secondary metabolites. In the present study, leaves and inflorescences previously used for the extraction of essential oils instead of being disposed of were subjected to extraction with supercritical CO2 after pretreatment with microwaves. An experimental design was followed to seek the best extraction condition with the objective function being the maximum total extract. Pressure and temperature were statistically significant factors, and the optimal extraction condition was 240 bar, 60 °C, and pretreatment at 30 °C. The applied mathematical models showed good adherence to the experimental data. The extracts obtained by supercritical CO2 were analyzed and the presence of coumarins was confirmed. The extract investigated for cytotoxicity against bladder tumor cells (T24) exhibited significant reduction in cell viability at concentrations between 6 and 12 μg/mL. The introduction of green technology, supercritical extraction, in the exploration of P. polystachyum as a source of coumarins represents a paradigm shift with regard to previous studies carried out with this species, which used organic solvents. Furthermore, the concept of circular bioeconomy was applied, i.e., the raw material used was the residue of a steam-distillation process. Therefore, the approach used here is in line with the sustainable exploitation of native plants to obtain extracts rich in coumarins with cytotoxic potential against cancer cells.

Extraction of Antioxidant Compounds from Brazilian Green Propolis Using Ultrasound-Assisted Associated with Low- and High-Pressure Extraction Methods

The demand for bee products has been growing, especially regarding their application in complementary medicine. Apis mellifera bees using Baccharis dracunculifolia D.C. (Asteraceae) as substrate produce green propolis. Among the examples of bioactivity of this matrix are antioxidant, antimicrobial, and antiviral actions. This work aimed to verify the impact of the experimental conditions applied in low- and high-pressure extractions of green propolis, using sonication (60 kHz) as pretreatment to determine the antioxidant profile in the extracts. Total flavonoid content (18.82 ± 1.15-50.47 ± 0.77 mgQE·g^-1), total phenolic compounds (194.12 ± 3.40-439.05 ± 0.90 mgGAE·g^-1) and antioxidant capacity by DPPH (33.86 ± 1.99-201.29 ± 0.31 µg·mL^-1) of the twelve green propolis extracts were determined. By means of HPLC-DAD, it was possible to quantify nine of the fifteen compounds analyzed. The results highlighted formononetin (4.76 ± 0.16-14.80 ± 0.02 mg·g^-1) and p-coumaric acid (<LQ-14.33 ± 0.01 mg·g^-1) as majority compounds in the extracts. Based on the principal component analysis, it was possible to conclude that higher temperatures favored the release of antioxidant compounds; in contrast, they decreased the flavonoid content. Thus, the obtained results showed that samples pretreated with 50 °C associated with ultrasound displayed a better performance, which may support the elucidation of the use of these conditions.

Cereal Waste Valorization through Conventional and Current Extraction Techniques-An Up-to-Date Overview

Nowadays, in the European Union more than 100 million tons of food are wasted, meanwhile, millions of people are starving. Food waste represents a serious and ever-growing issue which has gained researchers’ attention due to its economic, environmental, social, and ethical implications. The Sustainable Development Goal has as its main objective the reduction of food waste through several approaches such as the re-use of agro-industrial by-products and their exploitation through complete valorization of their bioactive compounds. The extraction of the bioactive compounds through conventional methods has been used for a long time, whilst the increasing demand and evolution for using more sustainable extraction techniques has led to the development of new, ecologically friendly, and high-efficiency technologies. Enzymatic and ultrasound-assisted extractions, microwave-assisted extraction, membrane fractionation, and pressure-based extraction techniques (supercritical fluid extraction, subcritical water extraction, and steam explosion) are the main debated green technologies in the present paper. This review aims to provide a critical and comprehensive overview of the well-known conventional extraction methods and the advanced novel treatments and extraction techniques applied to release the bioactive compounds from cereal waste and by-products.

Increasing the added value of vine-canes as a sustainable source of phenolic compounds: A review

Grapes represent one of the most produced fruit crops around the world leading to the generation of large amounts of vine-canes as a side product, with no current economically profitable application. However, vine-canes have been demonstrated to be natural sources of phenolic compounds with numerous health benefits associated, with several potential applications. Therefore, new ambitious applications focused on their re-use are needed, targeting a sustainable process that simultaneous produces functional products and mitigates the waste generation. This review gives to the readers a complete summary about the state of the art regarding the vine-canes extracts research. Vine-canes phenolic composition is addressed and related to the health benefits exhibited. This review comprises studies from the past two decades reporting the extraction processes to recover vine-cane phenolic compounds, including conventional and environmentally friendly technologies and discussing their advantages and disadvantages. The conditions that favour the extraction process for vine-cane polyphenols for each technique were also deeply explored for the first time, enabling to the reader apply only the best parameters to achieve the highest yields without huge investment in optimizations procedures. Furthermore, a correlation between the bioactive properties of the vine-cane extracts and their applications in multiple fields is also critically presented.

Methods used for extraction of plant volatiles have potential to preserve truffle aroma: A review

Truffles are considered one of the world's most highly prized foods mainly due to their desirable organoleptic properties and rarity. However, truffles are seasonal (harvested mostly in winter from June to August in the Southern Hemisphere and from December to February in the Northern Hemisphere) and extremely perishable. Truffles deteriorate rapidly showing undesirable changes within 10 days from harvest in aroma and visual appearance after harvest. The very short postharvest shelf life (about 7-10 days) limits the potential for export and domestic consumption all year round. Several preservation methods have been studied to prolong their shelf life without the loss of aroma. However, all traditional preservation techniques have their own shortcomings and remain challenging. The extraction of natural truffle aroma volatiles for food applications could be a potential alternative to replace the existing synthetic flavoring used for processed truffle products. Four commonly used extraction methods for recovering volatile compounds from plants, namely, supercritical carbon dioxide extraction, Soxhlet extraction, distillation, and cold pressing, are critically analyzed. Up to date, existing research about the extraction of aroma volatiles from truffles is limited in the literature but based on the volatility of the key truffle volatile compounds, supercritical carbon dioxide extraction may offer the best possibility so that a natural truffle-based product that can be used in food applications throughout the year can be made available.

Alternative Extraction and Downstream Purification Processes for Anthocyanins

Anthocyanins are natural pigments displaying different attractive colors ranging from red, violet, to blue. These pigments present health benefits that increased their use in food, nutraceuticals, and the cosmetic industry. However, anthocyanins are mainly extracted through conventional methods that are time-consuming and involve the use of organic solvents. Moreover, the chemical diversity of the obtained complex extracts make the downstream purification step challenging. Therefore, the growing demand of these high-value pigments has stimulated the interest in designing new, safe, cost-effective, and tunable strategies for their extraction and purification. The current review focuses on the potential application of compressed fluid-based (such as subcritical and supercritical fluid extraction and pressurized liquid extraction) and deep eutectic solvents-based extraction methods for the recovery of anthocyanins. In addition, an updated review of the application of counter-current chromatography for anthocyanins purification is provided as a faster and cost-effective alternative to preparative-scale HPLC.

An Overview of Bioactive Flavonoids from Citrus Fruits

Citrus species are one of the world’s popular fruit crops, cultivated all over the world for their economic and nutritional values. Citrus, like other fruits and vegetables, are an important source of several antioxidant molecules (polyphenols, ascorbic acid, and carotenoids) that can inhibit the harmful effects of free radicals on the human body; due to their functional values and health-promoting properties, Citrus species are considered valuable fruits not only in agri-food industry, but also in pharmaceutical industry. Flavonoids are among the major constituents of polyphenols found in different parts of Citrus fruits (skin, peels, seed, pulp membrane, and juice). Flavonoids have different biological properties (antiviral, antifungal, and antibacterial activities). Several studies have also shown the health-related properties of Citrus flavonoids, especially antioxidant, anticancer, anti-inflammation, anti-aging, and cardiovascular protection activities. In the present review, attempts are made to discuss the current trends of research on flavonoids in different Citrus species.

Combined ionic liquid and supercritical carbon dioxide based dynamic extraction of six cannabinoids from Cannabis sativa L

The potential of supercritical CO2 and ionic liquids (ILs) as alternatives to traditional extraction of natural compounds from plant material is of increasing importance. Both techniques offer several advantages over conventional extraction methods. These two alternatives have been separately employed on numerous ocassions, however, until now, they have never been combined for the extraction of secondary metabolites from natural sources, despite properties that complement each other perfectly. Herein, we present the first application of an IL-based dynamic supercritical CO2 extraction of six cannabinoids (CBD, CBDA, Δ9-THC, THCA, CBG and CBGA) from industrial hemp (Cannabis sativa L.). Various process parameters were optimized, i.e., IL-based pre-treatment time and pre-treatment temperature, as well as pressure and temperature during supercritical fluid extraction. In addition, the impact of different ILs on cannabinoid extraction yield was evaluated, namely, 1-ethyl-3-methylimidazolium acetate, choline acetate and 1-ethyl-3-methylimidazolium dimethylphosphate. This novel technique exhibits a synergistic effect that allows the solvent-free acquisition of cannabinoids from industrial hemp, avoiding further processing steps and the additional use of resources. The newly developed IL-based supercritical CO2 extraction results in high yields of the investigated cannabinoids, thus, demonstrating an effective and reliable alternative to established extraction methods. Ultimately, the ILs can be recycled to reduce costs and to improve the sustainability of the developed extraction process.

Comparison of the Biological Potential and Chemical Composition of Brazilian and Mexican Propolis

Propolis is a resinous substance collected by bees from plants and its natural product is available as a safe therapeutic option easily administered orally and readily available as a natural supplement and functional food. In this work, we review the most recent scientific evidence involving propolis from two countries (Brazil and Mexico) located in different hemispheres and with varied biomes. Brazil has a scientifically well documented classification of different types of propolis. Although propolis from Brazil and Mexico present varied compositions, they share compounds with recognized biological activities in different extraction processes. Gram-negative bacteria growth is inhibited with lower concentrations of different types of propolis extracts, regardless of origin. Prominent biological activities against cancer cells and fungi were verified in the different types of extracts evaluated. Antiprotozoal activity needs to be further evaluated for propolis of both origins. Regarding the contamination of propolis (e.g., pesticides, toxic metals), few studies have been carried out. However, there is evidence of chemical contamination in propolis by anthropological action. Studies demonstrate the versatility of using propolis in its different forms (extracts, products, etc.), but several potential applications that might improve the value of Brazilian and Mexican propolis should still be investigated.

Activity of Ethanolic and Supercritical Propolis Extracts in Corynebacterium pseudotuberculosis and Its Associated Biofilm

Corynebacterium pseudotuberculosis is the etiological agent of caseous lymphadenitis in small ruminants, a chronic disease characterized by the development of granulomas in superficial and visceral lymph nodes as well as in several organs. An important characteristic of the infection with this bacterium is the formation of a biofilm and the absence of effective antibiotic therapy against the disease. From this scenario, the objective of this study was to evaluate the susceptibility of C. pseudotuberculosis to conventional antibiotics and to red, green, and brown propolis extracts obtained by the supercritical and ethanolic extraction methods as well as its activity in the bacterial biofilm. The results of the sensitivity test using antibiotics indicated a sensitivity of C. pseudotuberculosis strains to the antimicrobial agents. The ethanolic extract of green propolis and the supercritical red propolis extract showed the best antibacterial activities against planktonic C. pseudotuberculosis. A lower antimicrobial activity of the brown propolis extract was identified. Propolis extracts were effective in interfering with the formation of the C. pseudotuberculosis biofilm but had little activity on the consolidated biofilm. In conclusion, propolis extracts are more effective against C. pseudotuberculosis in the planktonic stage, being able to interfere with the formation of bacterial biofilm. However, the action of propolis extracts in a sessile and structured microbial biofilm is reduced.

Green and Efficient Processing of Wood with Supercritical CO2: A Review

Wood processing is a crucial step of wood utilization, but the adding of environmentally hazardous feedstocks and the use of unreasonable technology allow it to harm the environment and human health. Supercritical CO2 (scCO2) is a non-toxic, odorless, and safe solvent, which is widely used in studies and industrial production, but there is no review summarizing wood processing with scCO2. The unique structure and chemical properties of wood combined with scCO2 technology produce positive results. In this paper, wood processing with scCO2 is summarized, including wood impregnation, wood drying, wood thermochemical conversion, and wood extraction. The green and efficient characteristics of wood processing with scCO2 are explained in detail for researchers, engineers, and investors to provide a clean wood processing method. Further study is needed to reduce its energy consumption and commercialize it eventually.

Multivariate optimization of a combined static and dynamic supercritical fluid extraction method for trace analysis of pesticides pollutants in organic honey

The intensive application of pesticides to increase crop production has resulted in contamination of the agricultural products. Due to their occurrence at trace levels and the complexity of food samples, analysis of pesticide residues requires selective and efficient sample preparation methods. For this purpose, an extraction method based on supercritical carbon dioxide and acetonitrile as entrainer solvent was developed for trace analysis of atrazine, diazinon, chlorothalonil, and deltamethrin pesticides in honey samples. A Box-Behnken experimental design was applied to optimize extraction variables including static extraction time (5-15 min), pressure (200-700 bar), and temperature (45-70°C). The optimum extraction conditions were found to be 11.5 min static extraction time, 252 bar, and 70°C. The proposed analytical method showed a good linearity (≥0.998), low limit of detection (0.005-0.009 mg/kg), and good extraction recovery (74-111%). The precision study of the proposed method at two concentration levels of each pesticides, 0.25 and 1.0 mg/kg was found to be in the ranges of 2.3-4.21% for intraday (n = 3) and 3.93-8.02% for interday precisions (n = 3). The developed method is promising for use in trace analysis of pesticides in complex food samples including honey.

Application of Fluids in Supercritical Conditions in the Polymer Industry

This article reviews the use of fluids under supercritical conditions in processes related to the modern and innovative polymer industry. The most important processes using supercritical fluids are: extraction, particle formation, micronization, encapsulation, impregnation, polymerization and foaming. This review article briefly describes and characterizes the individual processes, with a focus on extraction, micronization, particle formation and encapsulation. The methods mentioned focus on modifications in the scope of conducting processes in a more ecological manner and showing higher quality efficiency. Nowadays, due to the growing trend of ecological solutions in the chemical industry, we see more and more advanced technological solutions. Less toxic fluids under supercritical conditions can be used as an ecological alternative to organic solvents widely used in the polymer industry. The use of supercritical conditions to conduct these processes creates new opportunities for obtaining materials and products with specialized applications, in particular in the medical, pharmacological, cosmetic and food industries, based on substances of natural sources. The considerations contained in this article are intended to increase the awareness of the need to change the existing techniques. In particular, the importance of using supercritical fluids in more industrial methods and for the development of already known processes, as well as creating new solutions with their use, should be emphasized.

Preparation of phthalocyanine green nano pigment using supercritical CO2 gas antisolvent (GAS): experimental and modeling

Phthalocyanine green nano pigment was prepared using supercritical gas antisolvent (GAS) process based on the SC-CO₂ method. Thermodynamic models were developed to study the volume expansion and operating conditions of the GAS process. Peng-Robinson EoS were applied for binary (CO₂ and DMSO) and ternary (CO₂, DMSO, and pigment) systems. A Box-Behnken experimental design was used to optimize the process. Influences of temperature (308, 318 and 328 K), pressure (10, 15 and 20 MPa) and solute concentration (10, 40 and 70 mg/mL) were studied on the particles size and their morphology. The fine particles produced were characterized by SEM, DLS, XRD, FTIR and DSC. Experimental results showed a great reduction in size of pigment particles in comparison to the original particles. The mean particle sizes of nanoparticles were obtained to 27.1 nm after GAS based on SC-CO₂ method.

Deriving valorization of phenolic compounds from olive oil by-products for food applications through microencapsulation approaches: a comprehensive review

Nowadays, olive oil consumption is correlated to many health benefits, essentially due to the presence of antioxidants, especially phenolic compounds, which fostered its intensive production worldwide. During olive oil extraction, through continuous or discontinuous processes, many olive oil by-products are generated. These by-products constitute an environmental problem regarding its management and disposal. They are phytotoxic and biotoxic due to their high content of phenolic compounds, presenting contrastingly relevant health benefits due to their potent radical scavenging activities. In the framework of the disposal and management of olive oil by-products, treatment, and valorization approaches are found. As currently, the majority of the valorization techniques applied have a null market value, alternative strategies for the obtainment of innovative products as fortified foods are being investigated. The recovery and valorization strategies of olive oil by-products may comprise extraction and further encapsulation of bioactive compounds, as an innovative valorization blueprint of phenolic compounds present in these by-products. The majority of phenolic compounds present in olive oil by-products possess limited application on the food industry since they are promptly amended by environmental factors like temperature, pH, and light. Consequently, they must be protected previously ending in the final formulation. Prior to foods fortification with phenolic-rich extracts obtained from olive oil by-products, they should be protected through microencapsulation approaches, allowing a sustained release of phenolic compounds in the fortified foods, without losing their physicochemical properties. The combined strategies of extraction and microencapsulation will contribute to promoting the sustainability of the olive oil sector and aid the food industry to obtain reinvented added-value products.

Effect of Experimental Parameters on the Extraction of Grape Seed Oil Obtained by Low Pressure and Supercritical Fluid Extraction

Grape seeds are an important byproduct from the grape process. The objective of this work was to evaluate the effect of experimental parameters (temperature and time of pretreatment with ultrasound) to obtain grape seed oil using low pressure (Soxhlet-Sox and Bligh Dyer-BD) and high pressure (supercritical carbon dioxide-SFE) methods. The best condition for pretreatment of samples was 30 min of sonication at 30 °C before extraction by Sox or BD. Ultrasound pretreatment was efficient to increase oil extraction yield by 32.10 (Sox), 20.31 (BD) and 12.54% (SFE), depending on the extraction method used as well as, and certainly influenced the total phenolic concentration in 311 (Sox), 234 (BD), and 184 (SFE)%. Ten fatty acids were identified in the oils, the major ones being 18:2ω-6cis (linoleic 52.39%-63.12%), 16:0 (palmitic 20.22%-26.80%) and 18:0 (stearic 8.52%-13.68%). The highest epicatechin concentration was identified in the BD sample: 30-30 (150.49 ± 5.98mg/kg), which presented a concentration of ≥3 times compared to the control (56.68 ± 1.81mg/kg). Ultrasound pretreatment also contributed positively (56% and 99% increase) in the α-tocopherol content of the SFE: 30-30 and BD: 30-30 samples, respectively. The results indicate that the ultrasound pretreatment is a suitable technology to improve the quality of the oil from the grape seed.

Propolis: types, composition, biological activities, and veterinary product patent prospecting

Propolis is a resinous substance composed of a mixture of different plant parts and molecules secreted by bees. Chemically, it is defined as a complex matrix containing biologically active molecules with antibacterial, antifungal, antiviral, antiparasitic, hepatoprotective, and immunomodulatory activities. It is widely employed in cosmetic formulations and pharmaceutical products and is one of the most widely used natural products. However, the effects and strength of these biological activities depend on the chemical profile and composition of each propolis type. This composition is associated with the diversity of local flora, the place and period of collection, and the genetics of the bees. In this context, the objective of this review was to investigate the biological, chemical, and microbiological properties of propolis. A technological prospection was also performed on patents for products designed to be used in animal health. Our investigation shows that the literature contains diverse studies dedicated to comparing and describing the composition and therapeutic properties of propolis. These studies demonstrate the potential biological use of propolis in veterinary medicine, showing the applications of propolis extracts in different formulations. However, there are a low number of propolis-based veterinary products with a registered patent. Thus, the development of products based on propolis is a promising market to be exploited. © 2019 Society of Chemical Industry.

High Density Supercritical Carbon Dioxide for the Extraction of Pesticide Residues in Onion with Multivariate Response Surface Methodology

The excessive use of pesticides is a serious health problem due to their toxicity and bioaccumulation through the food chain. Due to the complexity of foods, the analysis of pesticides is challenging often giving large matrix effects and co-extracted compounds. To overcome this problem, a selective and “green” supercritical fluid extraction method was developed, using neat carbon dioxide as a solvent at pressures of up to 800 bars. A Box–Behnken response surface experimental design was used, with the independent variables of density (0.70−1.0 g mL⁻¹), temperature (40−70 °C), and volume (10−40 mL) of solvent, and the dependent variable of extracted amount of pesticides. The optimum extraction condition was found at the use of 29 mL of supercritical CO₂ at 0.90 g mL⁻¹ and 53 °C (corresponding to 372 bars of pressure). It was observed that increasing the density of CO₂ significantly increased the extraction recovery of endrin and 2,4′-dichlorodiphenyldichloroethane. Matrix-matched calibration curves showed satisfactory linearity (R² ≥ 0.994), and LODs ranged from 0.2 to 2.0 ng g⁻¹. Precision was lower than 11% and recoveries between 80%–103%. Thus, the developed method could efficiently be used for trace analysis of pesticides in complex food matrices without the use of organic solvents.

Recent developments in detoxication techniques for aristolochic acid-containing traditional Chinese medicines

Aristolochic acids (AAs) have attracted significant attention because they have been proven to be the culprits in the mass incidents of AA nephropathy that occurred in Belgium in 1993. From then on, the door to sales of medicines containing AAs has been closed. As aristolochic acid (AA)-containing traditional Chinese medicine (TCM) has a potent therapeutic effect on some diseases, research into detoxication techniques for AA-containing traditional Chinese medicines (TCMs) should be considered to be absolutely essential. Therefore, in this paper, the use of AA-containing TCMs has been investigated and detoxication techniques, such as, processing (Paozhi, Chinese name), compatibility (Peiwu, Chinese name), pressurized liquid extraction (PLE) and supercritical fluid extraction (SFE), have been reviewed in detail. A large number of relevant studies have been reviewed and it was found that processing with honey or alkaline salts is the most widely used method in practical production. As the AAs are a group of weak acids, relatively speaking, processing with alkaline salts can achieve a high rate of reduction of the AAs. Meanwhile, it is necessary to consider the compatibility of AA-containing TCMs and other herbal medicines. In addition, PLE and SFE can also achieve an excellent reducing rate for AAs in a much shorter processing time. Therefore, the promotion of alkaline salt processing technology should be strengthened in the future. At the same time, some advanced modern extraction technologies also have good potential and should be further studied.

Unorthodox crystalline drug salts via the reaction of amine-containing drugs with CO2

Drugs containing amine groups react with CO2 to form crystalline ammonium carbamates or carbamic acids. In this approach, both the cation and anion of the salt, or the neutral CO2 adduct, are derived from the parent drug, generating new crystalline versions in a 'masked' or prodrug form. It is proposed that this approach may serve as a valuable new tool in engineering the physical properties of drugs for formulation purposes.

Evaluation of the antioxidant profile and cytotoxic activity of red propolis extracts from different regions of northeastern Brazil obtained by conventional and ultrasound-assisted extraction

Propolis is a complex mixture of resinous and balsamic material collected from the exudates of plants, shoots, and leaves by bees. This study evaluated red propolis extracts obtained by conventional (ethanolic) extraction and ultrasound-assisted extraction of six samples from different regions of northeastern Brazil. The total phenolic compounds and flavonoids, in vitro antioxidant activity, concentration of formononetin and kaempferol and the cytotoxicity against four human tumor cell lines were determined for all twelve obtained extracts. Significant variations in the levels of the investigated compounds were identified in the red propolis extracts, confirming that the chemical composition varied according to the sampling region. The extraction method used also influenced the resulting propolis compounds. The highest concentration of the compounds of interest and the highest in vitro antioxidant activity were exhibited by the extracts obtained from samples from state of Alagoas. Formononetin and kaempferol were identified in all samples. The highest formononetin concentrations were identified in extracts obtained by ultrasound, thus indicating a greater selectivity for the extraction of this compound by this method. Regarding cytotoxic activity, for the HCT-116 line, all of the extracts showed an inhibition of greater than 90%, whereas for the HL-60 and PC3 lines, the minimum identified was 80%. In general, there was no significant difference (p>0.05) in the antiproliferative potential when comparing the extraction methods. The results showed that the composition of Brazilian red propolis varies significantly depending on the geographical origin and that the method used influences the resulting compounds that are present in propolis. However, regardless of the geographical origin and the extraction method used, all the red propolis samples studied presented great biological potential and high antioxidant activity. Furthermore, the ultrasound-assisted method can be efficiently applied to obtain extracts of red propolis more quickly and with high concentration of biomarkers of interest.

Green chemical engineering in China

In China, the rapid development greatly promotes the national economic power and living standard but also inevitably brings a series of environmental problems. In order to resolve these problems fundamentally, Chinese scientists have been undertaking research in the area of green chemical engineering (GCE) for many years and achieved great progresses. In this paper, we reviewed the research progresses related to GCE in China and screened four typical topics related to the Chinese resources characteristics and environmental requirements, i.e. ionic liquids and their applications, biomass utilization and bio-based materials/products, green solvent-mediated extraction technologies, and cold plasmas for coal conversion. Afterwards, the perspectives and development tendencies of GCE were proposed, and the challenges which will be faced while developing available industrial technologies in China were mentioned.

Chemical characterization and biological activity of six different extracts of propolis through conventional methods and supercritical extraction

Propolis is a natural product with many demonstrated biological activities and propolis extract has been used in the food, pharmaceutical and cosmetics industries. Different works have showed the variations in the chemical composition, and consequently, on the biological activity of the propolis that are associated with its type and geographic origin. Due to this study evaluated propolis extracts obtained through supercritical extraction and ethanolic extraction (conventional) in three samples of different types of propolis (red, green and brown), collected from different regions in Brazil (state of Bahia). Analyses were performed to determine the humidity, water activity, the content of total ash, proteins, lipids and fiber in raw propolis samples. The content of phenolic compounds, flavonoids, in vitro antioxidant activity (DPPH), catechin, ferulic acid and luteolin and antimicrobial activity against two bacteria (Staphylococcus aureus and Escherichia coli) were determined for all extracts. For the green and red ethanolic extracts the anti-leishmanicidal potential was also evaluated. The physicochemical profiles showed agreement in relation to the literature. The results identified significant differences among the extracts (p>0.05), which are in conformity with their extraction method, as well as with type and botanical origin of the samples. The extraction with supercritical fluid was not efficient to obtain extracts with the highest contents of antioxidants compounds, when compared with the ethanolic extracts. The best results were shown for the extracts obtained through the conventional extraction method (ethanolic) indicating a higher selectivity for the extraction of antioxidants compounds. The red variety showed the largest biological potential, which included the content of antioxidants compounds. The results found in this study confirm the influence of the type of the raw material on the composition and characteristics of the extracts. The parameters analysis were important to characterize and evaluate the quality of the different Brazilian propolis extracts based on the increased use of propolis by the natural products industry.

Preparation and Application of Standardized Typical Volatile Components Fraction from Turmeric (Curcuma longa L.) by Supercritical Fluid Extraction and Step Molecular Distillation

A green and reliable method using supercritical fluid extraction (SFE) and molecular distillation (MD) was optimized for the separation and purification of standardized typical volatile components fraction (STVCF) from turmeric to solve the shortage of reference compounds in quality control (QC) of volatile components. A high quality essential oil with 76.0% typical components of turmeric was extracted by SFE. A sequential distillation strategy was performed by MD. The total recovery and purity of prepared STVCF were 97.3% and 90.3%, respectively. Additionally, a strategy, i.e., STVCF-based qualification and quantitative evaluation of major bioactive analytes by multiple calibrated components, was proposed to easily and effectively control the quality of turmeric. Compared with the individual calibration curve method, the STVCF-based quantification method was demonstrated to be credible and was effectively adapted for solving the shortage of reference volatile compounds and improving the QC of typical volatile components in turmeric, especially its functional products.

Supercritical Regeneration of an Activated Carbon Fiber Exhausted with Phenol

The properties of supercritical CO2 (SCCO2) and supercritical water (SCW) turn them into fluids with a great ability to remove organic adsorbates retained on solids. These properties were used herein to regenerate an activated carbon fiber (ACF) saturated with a pollutant usually contained in wastewater and drinking water, phenol. Severe regeneration conditions, up to 225 bar and 400 °C, had to be employed in SCCO2 regeneration to break the strong interaction established between phenol and the ACF. Under suitable conditions (regeneration temperature, time, and pressure, and flow of SCCO2) the adsorption capacity of the exhausted ACF was completely recovered, and even slightly increased. Most of the retained phenol was removed by thermal desorption, but the extra percentage removed by extraction allowed SCCO2 regeneration to be significantly more efficient than the classical thermal regeneration methods. SCCO2 regeneration and SCW regeneration were also compared for the first time. The use of SCW slightly improved regeneration, although SCW pressure was thrice SCCO2 pressure. The pathways that controlled SCW regeneration were also investigated.