Phenolic-Compound-Extraction Systems for Fruit and Vegetable Samples

Natural products have served as major sources of drugs for centuries, and about half of the pharmaceuticals in use today are derived from natural products. Therefore, screening and analysis of the bioactive components in medicinal plants are now indispensable for the discovery of new drugs and quality control of plant pharmaceuticals. Sample preparation is essential for isolating desired components from complex matrices and greatly influences the reliable and accurate analysis of plant-derived medicines. This review will summarize current trends in sample preparation techniques for the analysis of plant-derived medicines, focusing primarily on newly developed techniques, such as ultrasonic extraction (USE), microwave-assisted extraction (MAE), pressurized-liquid extraction (PLE), supercritical- fluid extraction (SFE), solid-phase extraction (SPE), solid-phase microextraction (SPME), and liquid-phase microextraction (LPME). The general characteristics and applications of each method in the analysis of plant-derived medicines are described. Keywords: Medicinal plants, Traditional Chinese medicines, Microwave-assisted extraction, Pressurized-liquid extraction, Supercritical-fluid extraction, Solid-phase extraction, Solid-phase microextraction, Liquid-phase microextraction, bioactive components, ultrasonic extraction (USE), microwave-assisted extraction (MAE), pressurized-liquid extraction (PLE), supercritical-fluid extraction (SFE), solid-phase extraction (SPE), solid-phase microextraction (SPME), liquid-phase microextraction (LPME), High-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), high-speed countercurrent chromatography (HSCCC), capillary electrophoresis (CE), finger print analysis (FA), ultraviolet (UV) spectrometry, fluorescence (FL) spectrometry, evaporative light scattering (ELS) spectrometry, mass spectrometry (MS), tandem mass spectrometry (MS-MS), nuclear magnetic resonance (NMR), Optimal solid, –, liquid extraction (SLE), freeze-dried, Soxhlet extraction, liquid-liquid extraction (LLE), microwave distillation (MD), pressurized hot water extraction (PHWE), matrix solid-phase dispersion (MSPD), ultrasound-assisted extraction (UAE), plant-derived medicines, antioxidant properties, superheated water extraction (SWE), CO2-based fluids

Phenolic compounds are a group of secondary metabolites produced by plants under stressful conditions. Phenolic compounds play an important role in the prevention and treatment of certain illnesses and are exploited by the food and pharmaceutical industries. Conventional methods are commonly used as models to compare the efficiencies of alternative extraction methods. Among alternative extraction processes, microwave-assisted extraction (MAE), pressurized liquid extraction (PLE), supercritical fluid extraction (SFE) and ultrasonic-assisted extraction (UAE) are the most studied. These methods produce extracts rich in phenolic compounds using moderate temperatures, short extraction times, and solvents generally recognized as safe. The combination of extraction time and temperature plays a critical role in the stability of the compounds. Solvents of higher polarity enhance the extraction of phenolic compounds. The use of the ethanol-water mixture for MAE, PLE, and UAE is recommended. MAE and UAE involve shorter extraction times than do PLE and SFE. SFE requires a low average temperature (40°C). MAE produces the highest total phenolic content [227.63mgGAE/g dry basis (d.b.)], followed by PLE (173.65mgGAE/g d.b.), UAE (92.99mgGAE/g d.b.) and SFE (37mgGAE/g d.b.). Extraction yields and recovery rates of the phenolic compounds can be enhanced by combining and integrating extraction methods.

Microwave-assisted extraction (MAE) has been recognised as a powerful potential alternative for the extraction of active compounds from plant materials compared to other advanced methods such as ultrasound-assisted extraction (UAE), pressurised liquid extraction (PLE), supercritical fluid extraction (SFE), and Soxhlet. The advantages of MAE processing technique are reduced processing time, higher yield, lower usage of solvent, and smaller energy demand. Nevertheless, most researchers used organic solvents which have toxic effect on the environment. Therefore, in this study, distilled water was used as a natural solvent in the sample preparation. Pitaya peel is a form of potential fruit waste, especially in the food industry. Notably, its liquid extract can be applied as natural colouring and it contains beneficial active compounds that have commercial value. Wastage during the processing of food is inevitable and disposal can be a major problem for the industry and the society. Negative impacts such as pollution to the environment, hazards to human health, and loss of income to the waste generator may occur. Thus, extraction can be an effective solution for minimising waste produced by the food processing industry. Food waste often contain several usable substances of high value including some of that are beneficial for health such as mineral contents and phenolic compounds. The aim of this research was to find the optimal operating parameters for extraction of total phenolic content (TPC) from pitaya peel using MAE method. These parameters were the (1) weight of the sample, (2) temperature, (3) power, and (4) extraction time. In this research, the results showed that the best condition for the parameters of MAE were at the power of 400 W, temperature of 45 °C, and 20 min contact time when extracting 1.2 g pitaya peel in 50 mL distilled water. These figures were validated through statistical analysis using SPSS with Bonferroni post hoc tests. The TPC presented in the liquid extract was measured in GAE/g. In addition, the Inhibitory Concentration (IC50) of the liquid extract was determined by applying the best condition for the parameters of MAE and DPPH reagent as the synthetic free radical. The IC50 value obtained in this research was 0.52 mg/mL.

Background: Alkaloids are bioactive nitrogenous compounds with significant pharmacological applications, including analgesic, anti-inflammatory, anticancer, neuroprotective, and antimicrobial effects. Conventional extraction methods rely on toxic organic solvents, leading to environmental concerns and inefficiencies in yield and purity. The adoption of green extraction technologies, such as Supercritical Fluid Extraction (SFE), Microwave-Assisted Extraction (MAE), and Ultrasound-Assisted Extraction (UAE), offers a sustainable and efficient alternative. These methods enhance extraction efficiency, reduce processing time, and minimize solvent toxicity, ensuring safer and more effective therapeutic applications. Objective: This study aimed to evaluate and compare the efficiency of SFE, MAE, and UAE in the extraction, isolation, and purification of alkaloids from Papaver somniferous and Erythroxylon coca. The focus was on optimizing extraction conditions to maximize yield, purity, and recovery while minimizing environmental impact. Methods: Plant materials were sourced from authenticated suppliers, processed into fine powder, and stored under controlled conditions. SFE, MAE, and UAE were performed under optimized conditions, with SFE utilizing CO₂ as a supercritical solvent at 40°C and 2500 psi with a 12 g/min flow rate. The extracted alkaloids were quantified using UV-Vis spectrophotometry and high-performance liquid chromatography (HPLC) with an Agilent C18 reverse-phase column and a mobile phase of acetonitrile-water (50:50) at a flow rate of 1.0 mL/min. Statistical analysis, including one-way ANOVA and Tukey’s HSD post hoc test, was conducted to determine significant differences in extraction performance (p < 0.05). Recovery rates, purity levels, and solvent consumption were also assessed for each method. Results: SFE yielded the highest alkaloid concentrations, with P. somniferous producing 25.7 mg/g of morphine and 18.3 mg/g of codeine, outperforming MAE (22.4 mg/g and 15.2 mg/g) and UAE (19.5 mg/g and 13.1 mg/g). E. coca yielded 30.4 mg/g of cocaine via SFE, significantly higher than MAE (26.8 mg/g) and UAE (23.5 mg/g). HPLC purity analysis showed SFE resulted in 97% purity for morphine, 91% for codeine, and 98% for cocaine, surpassing MAE (91%, 87%, and 93%) and UAE (87%, 83%, and 89%). Recovery rates were highest for SFE (96.8% for P. somniferous, 95.6% for E. coca), exceeding those of MAE (93.4%, 91.8%) and UAE (90.1%, 88.2%). Solvent consumption was lowest for SFE, requiring only 15 mL per gram of alkaloid, compared to MAE (27 mL) and UAE (34 mL). The coefficient of variation (CV) was lowest for SFE (4.1%), demonstrating superior precision over MAE (5.7%) and UAE (7.2%). Conclusion: This study confirms that SFE is the most effective, precise, and environmentally sustainable technique for alkaloid extraction, yielding the highest purity and recovery rates while minimizing solvent waste and environmental impact. The findings support the adoption of green extraction methodologies for large-scale pharmaceutical applications, ensuring safer and more efficient production of high-purity alkaloids for therapeutic use.

The extensive use of antibiotics and vaccines against microbial infections can result in long-term negative effects on humans and the environment. However, there are a number of plants that have antimicrobial effects against various disease-causing microbes such as bacteria, viruses, and fungi without negative side effects or harm to the environment. In this regard, four particular plants- Capsicum, Nigella sativa, Musa paradisiaca L., and Citrus limetta have been widely considered due to their excellent antimicrobial effect and ample availability. In this review, we discuss their antimicrobial effects due to the presence of thymoquinone, p-cymene, pinene, alkaloids, limonene, camphene, and melanin. These antimicrobial compounds disrupt the cell membrane of microbes, inhibit cellular division, and form biofilm in bacterial species, eventually reducing the number of microbes. Extraction of these compounds from the respective plants is carried out by different methods such as soxhlet, hydro-distillation, liquid-liquid extraction (LLE), pressurized liquid extraction (PLE), solid-phase extraction (SPE), supercritical fluid extraction (SFE), pulsed electric field (PEF), microwave-assisted extraction (MAE), enzyme-assisted extraction (EAE), ultrasound-assisted extraction (UAE), and high-voltage electrical discharge. Suitable selection of the extraction technique highly depends upon the associated advantages and disadvantages. In order to aid future study in this field, this review paper summarizes the advantages and disadvantages of each of these approaches. Additionally, the discussion covers how antimicrobial agents destroy harmful bacteria. Thus, this review offers in-depth knowledge to researchers on the antibacterial properties of Capsicum, Nigella sativa, Musa paradisiaca L. peels, and Citrus limetta.

Natural phenolic compounds are important classes of plant, microorganism, and algal secondary metabolites. They have well-documented beneficial biological activities. The marine environment is less explored than other environments but have huge potential for the discovery of new unique compounds with potential applications in, e.g., food, cosmetics, and pharmaceutical industries. To survive in a very harsh and challenging environment, marine organisms like several seaweed (macroalgae) species produce and accumulate several secondary metabolites, including marine phenolics in the cells. Traditionally, these compounds were extracted from their sample matrix using organic solvents. This conventional extraction method had several drawbacks such as a long extraction time, low extraction yield, co-extraction of other compounds, and usage of a huge volume of one or more organic solvents, which consequently results in environmental pollution. To mitigate these drawbacks, newly emerging technologies, such as enzyme-assisted extraction (EAE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), pressurized liquid extraction (PLE), and supercritical fluid extraction (SFE) have received huge interest from researchers around the world. Therefore, in this review, the most recent and emerging technologies are discussed for the extraction of marine phenolic compounds of interest for their antioxidant and other bioactivity in, e.g., cosmetic and food industry. Moreover, the opportunities and the bottleneck for upscaling of these technologies are also presented.

Extraction techniques are continuously developed by the scientific community. Meanwhile, avocado peel is a by-product of avocado processing and a source of bioactive compounds. The purpose of this review was to summarize the use of advanced techniques for extracting bioactive compounds from avocado peel to help understand which techniques have and have not been applied to avocado peel. Three primary databases were used to collect the information, including Google Scholar, Scopus, and Web of Science, by using the keywords “avocado”, “peel”, and “extraction”. Additional keywords related to the extraction technique were also used, including “Microwave-Assisted Extraction”, “Ultrasound-Assisted Extraction”, “Enzyme-Assisted Extraction”, “Pressurized Liquid Extraction”, “Supercritical Fluid Extraction”, “Natural Deep Eutectic Solvents”, “Three-phase partitioning (TPP)”, “Pulsed-Electric Field”, “High Voltage Electric Discharge Plasma”, “Centrifugal Partition Extraction”, and “Surfactant-Mediated Extraction”. The results show that microwave-assisted extraction, ultrasound-assisted extraction, enzyme-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, TPP, and natural deep eutectic solvent extraction have been used to retrieve bioactive compounds from avocado peel. Other techniques have not yet been applied for the extraction of bioactive compounds from avocado peel. This article is the first review discussing the advanced extraction technique for retrieving bioactive compounds from avocado peel. This article creates a paradigm for future studies.

The increasing production of tropical fruits followed by their processing results in tons of waste, such as skins or seeds. However, these by-products have been reported to be rich in bioactive compounds (BACs) with excellent properties of interest in the cosmeceutical industry: antioxidant, anti-aging, anti-inflammatory, antimicrobial and photoprotective properties. This review summarizes the tropical fruits most produced worldwide, their bioactive composition and the most important and studied therapeutic properties that their by-products can contribute to skin health, as well as the different approaches for obtaining these compounds using techniques by conventional (Soxhlet, liquid-liquid extraction or maceration) and non-conventional extractions (supercritical fluid extraction (SFE), ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), pressurized liquid extraction (PLE) and two-phase aqueous system), followed by their identification by HPLC-MS or GC-MS analysis. Moreover, this work encompasses several studies that may prove the effects of seeds and skins from tropical fruits against oxidative stress, hyperpigmentation, acne, aging or UV radiation. Therefore, the investigation of functional components present in tropical fruit by-products under a circular bioeconomy model could be of great interest for the cosmeceutical industry and a very promising option for obtaining new cosmeceutical formulations.

A simple, inexpensive and sensitive method was developed for the simultaneous determination of three pesticide residues (carbendazim, thiophanate-methyl, and imidacloprid) in fruit and vegetable samples using high performance liquid chromatography (HPLC) based on a combined pretreatment of ultrasound-assisted deep eutectic solvent extraction (UA-DES-E) and liquid-liquid extraction (LLE). In this study, various types of deep eutectic solvents (DESs) were synthesized and the extraction efficiency was compared as extraction solvents. Results showed that glycerol-proline = 9:4 (GP-5) obtained the highest extraction efficiency among different types of DESs. Experiment conditions, including DES volume, extraction time and pH, were systematically optimized using single-factor experiment. Under the optimum conditions, the limits of detection (LODs) and quantification (LOQs) were in the ranges of 0.05–0.2 μg·mL−1 and 0.1–0.5 μg·mL−1, respectively. The relative recoveries of the three pesticides in the fruit and vegetable samples ranged from 85.7 to 113.0% at two spiked levels. Meanwhile, the method achieved excellent linearity with determination coefficients (r) greater than 0.999. Furthermore, the method was successfully applied to the analysis of the pesticides in real fruit and vegetable samples (apple, tomato, and grape).

Plant protein extraction is vital in biotechnology, pharmaceuticals, and functional foods, where protein functionality directly influences downstream applications. Conventional extraction methods are limited by long processing times, high solvent consumption, and potential degradation of protein bioactivity, necessitating more efficient and protein-preserving approaches. This review (encompassing studies published from 2015 to 2025) evaluates advanced extraction technologies with emphasis on efficiency, sustainability, and preservation of protein functionality. Key strategies include ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and enzyme-assisted extraction (EAE) methods, as well as pulsed electric fields (PEF), supercritical fluid extraction (SFE), ionic liquid extraction (ILE), deep eutectic solvents (DES), pressurized liquid extraction (PLE), three-phase partitioning (TPP), detergent-assisted adsorption, and reversed micellar extraction (RME). These approaches employ physical, chemical, or enzymatic mechanisms to improve efficiency, minimize solvent use, and better preserve protein integrity. UAE, MAE, and EAE increase protein yields and improve functional traits such as solubility, emulsification, and antioxidant activity, while PEF and SFE mainly enhance solubility and purity. ILE and DES are notable for their environmental sustainability, whereas PLE, TPP, and RME combine high yields with faster processing and improved bioactivity preservation. These techniques have demonstrated effectiveness across diverse plant matrices, highlighting their versatility for both research and industrial applications. Emerging trends emphasize the optimization of extraction processes to balance high yields with protein bioactivity, offering valuable insights for developing efficient, sustainable, and environmentally friendly methods in plant-based protein production.

The pesticide residues in foods have received increasing attention as one of the most important food safety issues. Therefore, more strict regulations on the maximum residue limits (MRLs) for pesticides in foods have been established in many countries and health organizations, based on the sensitive and reliable analysis methods of pesticide residues. However, the analysis of pesticide residues is a continuing challenge mainly because of the small quantities of analytes as well as the large amounts of interfering substances which can be co-extracted with them, often leading to experimental errors and damage to the analytical instruments. Thus, extensive sample preparation is often required for the pesticide residue analysis for the effective extraction of the analytes and removal of the interferences. This paper focuses on reviewing the recent development in the sample preparation methods for the pesticide residue analysis in foods since 2006. The methods include: liquid-liquid extraction (LLE), supercritical-fluid extraction (SFE), pressurized-liquid extraction (PLE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), gel permeation chromatography (GPC), solid-phase extraction (SPE), molecularly imprinted polymers (MIPs), matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME), QuEChERS, cloud point extraction (CPE) and liquid phase micro-extraction (LPME), etc. Particularly their advantages, disadvantages and future perspectives will be discussed.

Green techniques for extraction of bioactive carbohydrates

Non-thermal extraction techniques their own strengths by enhancing the extraction process in different ways and ensuring better quality and yield of extracted compounds across various fields. Pressurized liquid extraction (PLE) and supercritical fluid extraction are both very effective and precise. PLE uses high pressure to make the solvent more powerful, which helps to extract a lot of different compounds quickly without causing damage. Supercritical fluid extraction uses fluids at supercritical conditions to target specific compounds, ensuring high purity and efficiency. Ultrasound-assisted extraction (UAE) and radiation-assisted extraction are known for their speed and effectiveness. UAE uses sound waves to create bubbles that break open cells, allowing the solvent to extract compounds more quickly. Radiation-assisted extraction, such as microwave-assisted extraction, heats the solvent rapidly to boost extraction rates while protecting delicate compounds from excessive heat. Subcritical fluid extraction is both flexible and eco-friendly. It uses fluids at lower temperatures and pressures, making it suitable for extracting a wide range of compounds and reducing the environmental impact by using less solvent and energy. Cold plasma-assisted extraction is a newer and an innovative method for extracting compounds that can be damaged by heat. It uses a special type of gas at low temperatures to help release sensitive compounds without applying heat. Overall, exploring these non-thermal extraction techniques shows how they can enhance extraction processes, improve the quality and yield of extracted compounds, and offer more sustainable and efficient options across different industries.

Marine macroalgae are rich in bioactive compounds that can be applied in several fields, mainly food, cosmetics, and medicine. The health-promoting effects of bioactive compounds, such as polyphenols, polysaccharides, carotenoids, proteins, and fatty acids, have been increasingly explored, especially regarding their antioxidant activity and improvement in human health. To extract these valuable compounds, advanced technologies that include Supercritical-Fluid Extraction (SFE), Pressurised-Liquid Extraction (PLE), Ultrasound-Assisted Extraction (UAE), Microwave-Assisted Extraction (MAE), Enzyme-Assisted Extraction (EAE), Ultrasound-Microwave-Assisted Extraction (UMAE) and Liquefied Gas Extraction (LGE) have been assessed due to their notable advantages over the conventional methods (Solid-Liquid and Soxhlet extraction). These advanced techniques are considerably influenced by different extraction parameters such as temperature, pressure, type of solvent, extraction time, solvent:solid material ratio, power (MAE, UAE, and UMAE), enzymes used (EAE), and factors related to the macroalgae matrix itself. Optimizing these process parameters for each method is critical to obtain better efficiency results for the targeted bioactive compounds. Macroalgae are natural sources with undeniable beneficial effects on human health. In this context, optimising the extraction techniques discussed in this review should prioritise exploiting these valuable resources' wide range of bioactive properties.

This review emphasizes innovative techniques for extraction of essential oils, including ultrasound-assisted, supercritical fluid, enzyme-assisted, pressurized liquid, and microwave-assisted extraction methods. An analysis is performed on fundamental operational characteristics highlighting its advantages and limitations in terms of environmental impact, selectivity, and efficiency. Supercritical fluid extraction uses supercritical carbon dioxide in a solvent-free approach, enabling controlof solvating capacity to obtain high-purity extracts. This technique facilitates extraction of essential oils from spices such as turmeric and clove. Enzyme-assisted extraction breaks down cell walls and promotes release of essential oils from black pepper and cardamom usingspecific enzymes such as cellulase and protease. Pressurized liquid extraction uses increased temperatures and pressures to enhance penetration and solubility of solvents. Application of ultrasound and microwaves effectively enhances mass transfer rates and reduces extraction periods utilizing ultrasonic and electromagnetic radiation. This investigation contributes to efficient, eco-friendly, and cost-effective methods for essential oil extraction.