This article provides a critical narrative review of the literature concerning extraction techniques for natural products. It is not intended to be a systematic review following PRISMA guidelines, but rather a comprehensive overview to identify current trends, challenges, and future perspectives. The literature was surveyed using major scientific databases, including Scopus, PubMed, and Google Scholar, with a primary focus on publications from the last 2 decades to cover recent advancements. However, seminal, highly-cited foundational papers from before this period were also included to provide essential historical context. Keywords used for the search included, but were not limited to: “natural product extraction,” “phytochemicals,” “bioactivity,” “ultrasound-assisted extraction,” “microwave-assisted extraction,” “supercritical fluid extraction,” “hybrid methods,” and “synergy.” The primary inclusion criterion was peer-reviewed research and review articles published in English that provided significant insights into extraction principles, applications, and challenges. Conference abstracts, patents, and non-English articles were excluded from this review.

Extraction methods significantly impact the solubility, stability, and concentration of bioactive compounds (Zhang et al., 2020). Conventional approaches, which are discussed in detail in Section 3, include traditional methods such as maceration, Soxhlet extraction, and hydrodistillation. While these techniques have been used for decades, they often suffer from low efficiency, high solvent consumption, and long extraction times (Dhobi et al., 2009). Moreover, heat-sensitive compounds such as polyphenols, flavonoids, and terpenoids are prone to degradation under prolonged exposure to high temperatures (Valisakkagari et al., 2024).

Modern advanced extraction techniques have been developed to overcome these limitations by enhancing extraction efficiency, reducing solvent use, and preserving bioactive integrity (Khaw et al., 2017). Depending on the method used, the composition of extracted phytochemicals can vary significantly (Kumar et al., 2023):

Solvent-based extractions are highly dependent on polarity, with polar solvents (e.g., ethanol, water) favoring hydrophilic compounds (e.g., flavonoids, tannins) and non-polar solvents (e.g., hexane, chloroform) extracting lipophilic bioactives (e.g., terpenoids, carotenoids) (Da Silva et al., 2022).

Mechanically-assisted extractions (e.g., ultrasound and microwave methods) enhance cell wall disruption, facilitating the release of intracellular compounds while minimizing structural degradation (Rocchetti et al., 2022).

Enzyme-assisted methods improve the selective extraction of glycosides, polysaccharides, and other cell wall-associated compounds, increasing bioavailability (Wang et al., 2024).

The biological activity of plant extracts is influenced not only by the presence of bioactive compounds but also by their structural stability and bioavailability, which extraction methods affect (Usman et al., 2022). Studies comparing different extraction techniques have shown that optimized methods lead to higher antioxidant, anti-inflammatory, and antimicrobial effects due to the enhanced recovery of functional phytochemicals (Kumar et al., 2023).

The superiority of modern techniques is well-illustrated by flavonoid extraction from citrus peels. Conventional Soxhlet extraction requires prolonged heating at the solvent’s boiling point (e.g., ∼78°C for ethanol), which can cause thermal degradation of sensitive compounds (Ćujić et al., 2016). In contrast, UAE utilizes acoustic cavitation at lower temperatures, enabling a more efficient recovery of these phytochemicals (Chemat et al., 2017). Consequently, UAE extracts from citrus peels consistently show higher yields of flavonoids and superior antioxidant activity (Khan et al., 2010). This is therapeutically significant, as these flavonoids, such as hesperidin, are known to possess potent anti-inflammatory effects which are compromised by heat (Parhiz et al., 2015; Al-Khayri et al., 2022).

Antioxidant Properties: Extraction techniques that efficiently retain polyphenols and flavonoids result in higher free radical scavenging potential, reducing oxidative stress (Brglez Mojzer et al., 2016).

Anti-Inflammatory Effects: Enhanced recovery of terpenoids and phenolic acids con-tributes to modulation of pro-inflammatory pathways [e.g., inhibition of Nuclear Factor-kappa B (NF-κB), Cyclooxygenase-2 (COX-2) enzymes] (da Cunha et al., 2022).

Antimicrobial Properties: The preservation of alkaloids, tannins, and saponins through optimized extraction enhances their antibacterial and antifungal effects, preventing microbial contamination in food and pharmaceutical applications (Oulahal and Degraeve, 2022).

Additionally, extraction efficiency is linked to particle size, solvent polarity, and processing conditions. For example:

Reducing particle size increases the surface area for solvent penetration, improving yield (Singh, 2017).

Selecting the appropriate solvent ensures maximum solubility of the target compounds while minimizing unwanted co-extractions (Reis et al., 2020).

Although advanced extraction methods improve efficiency and bioactivity, achieving batch-to-batch consistency remains a challenge. Several factors contribute to variations in extract quality:

Raw Material Variability: Differences in geographical origin, cultivation practices, and harvesting conditions affect phytochemical composition (Tiwari and Cummins, 2013).

Processing Inconsistencies: Variability in temperature, solvent selection, and extraction duration influences final extract quality (Rajha et al., 2014).

Regulatory Compliance: Standardization is crucial for pharmaceutical and nutraceutical applications, necessitating the use of analytical validation techniques (HPLC, GC-MS, NMR) (Durazzo et al., 2022).

Emerging research suggests that combining multiple extraction techniques can maximize compound yield and functional properties. The rationale behind integrated or “hybrid” extraction strategies is to leverage the unique advantages of multiple techniques to create a synergistic effect that a single method cannot achieve (Chemat et al., 2019a). A prime example is the sequential combination of EAE and UAE. EAE can be initially employed to enzymatically degrade the rigid cellulose and pectin matrix of the plant cell wall, creating a more porous structure (Muniglia et al., 2014). Subsequently, the acoustic cavitation generated by UAE can penetrate this pre-weakened matrix more effectively, leading to a dramatic increase in the release of intracellular bioactive compounds (Kumar et al., 2021). This synergy allows for higher yields at lower temperatures and shorter times than either EAE or UAE could accomplish alone (Puri et al., 2012; Xiong et al., 2019).

In addition to this EAE-UAE combination, other hybrid approaches have also demonstrated significant potential. These include:

Microwave-assisted hydrodistillation (MAHD): This method integrates microwave heating into the hydrodistillation process. The rapid, internal heating generated by microwaves shortens the distillation time significantly and can improve the yield and quality of essential oils compared to traditional hydrodistillation alone (Lucchesi et al., 2004; Golmakani and Rezaei, 2008).

Supercritical fluid extraction with a co-solvent (SFE-CO₂ w/co-solvent): While not a sequential hybrid method, this approach “integrates” a polar co-solvent (like ethanol) into the non-polar SC-CO₂ fluid. This dramatically enhances the extraction efficiency for moderately polar compounds, such as certain flavonoids and phenolic acids, which are poorly soluble in pure SC-CO₂ (Gallego et al., 2019; Paucar et al., 2023).

However, these integrated approaches are not without significant trade-offs that require critical consideration. Combining multiple techniques inevitably increases process complexity, the number of parameters to optimize, and overall operational costs, which can be a barrier for industrial scale-up (Nde and Foncha, 2020; Ahangari et al., 2021). For instance, a hybrid SFE-ultrasound system requires high-pressure equipment coupled with a high-power ultrasonic transducer, representing a substantial capital investment (De Melo et al., 2014). Furthermore, a multi-step process introduces additional potential points of failure and may increase total processing time, even if individual steps are rapid. Therefore, the decision to implement a hybrid system must be justified by a significant and measurable improvement in yield, purity, or bioactivity that outweighs these practical and economic challenges (Chemat et al., 2019a).

Maceration is one of the simplest and most commonly used extraction methods, involving soaking plant material in a suitable solvent at room temperature for an extended period (Hidayat and Wulandari, 2021). This technique allows for the passive diffusion of bioactive compounds into the solvent (Chongo, 2025). However, it is highly time-consuming and often leads to incomplete extraction (Shikov et al., 2022). Additionally, maceration may result in the co-extraction of undesirable compounds, affecting the purity and bioactivity of the final extract (Chuo et al., 2022).

Soxhlet extraction is a continuous solvent extraction technique that involves repeated percolation of hot solvent over the plant material (López-Bascón and De Castro, 2020). This method increases extraction efficiency compared to maceration by continuously replenishing the solvent, allowing for better solubility and diffusion of target compounds (Şahin et al., 2011). However, its major drawback is the prolonged exposure to high temperatures, which can degrade heat-sensitive bioactive compounds such as polyphenols and flavonoids (Antony and Farid, 2022). Additionally, Soxhlet extraction requires a large volume of solvent, making it less environmentally friendly and cost-effective (Trolles-Cavalcante et al., 2021).

Hydrodistillation is primarily used for extracting essential oils and volatile compounds from plant materials (Abbas et al., 2017). This method involves boiling plant material in water or steam to release volatile compounds, which are then condensed and collected (Perović et al., 2024). While effective for obtaining essential oils, hydrodistillation poses challenges such as the loss of thermolabile compounds, emulsification issues, and long processing times (Pheko-Ofitlhile and Makhzoum, 2024). Furthermore, the high temperatures used in hydrodistillation can alter the chemical composition of extracted oils, affecting their bioactivity and fragrance profile (Lainez-Cerón et al., 2021) (Figure 1).

Solvent choice is one of the most critical factors in determining extraction efficiency. The polarity of the solvent plays a key role in selecting specific classes of bioactive compounds:

Polar solvents (e.g., water, ethanol, methanol) efficiently extract hydrophilic compounds such as flavonoids, polyphenols, and anthocyanins (Tzanova et al., 2020).

Non-polar solvents (e.g., hexane, chloroform, ethyl acetate) are better suited for lipophilic bioactives such as terpenoids, carotenoids, and essential oils (Siddiqui et al., 2024).

Binary or ternary solvent systems (e.g., ethanol-water mixtures) enhance the extraction of a broad range of phytochemicals, improving both yield and bioactivity (Natolino et al., 2024).

The critical role of solvent polarity and the benefits of mixed-solvent systems are well-illustrated by the extraction of polyphenols from green tea (Camellia sinensis). For instance, a study demonstrated that using a 70% ethanol-water mixture yielded significantly higher total phenolic content and antioxidant activity compared to using either pure water or absolute ethanol (Calderón-Oliver and Ponce-Alquicira, 2021; Maslov et al., 2022). Pure water primarily extracts highly polar compounds, while absolute ethanol is less effective for these (Cheng et al., 2021). The ethanol-water mixture, however, creates a solvent environment with intermediate polarity, capable of efficiently extracting a wider spectrum of polyphenols, which in turn leads to enhanced synergistic bioactivity (Plaskova and Mlcek, 2023). This highlights the necessity of optimizing solvent systems to match the polarity of the target bioactive compounds.

In recent years, green solvents (defined as environmentally benign solvents, typically derived from renewable resources, that are characterized by low toxicity, biodegradability, and high efficiency) have gained attention for their eco-friendly and efficient extraction capabilities. Among these, Deep Eutectic Solvents (DES), typically formed from natural compounds like choline chloride and organic acids, are emerging as promising alternatives to volatile organic solvents (Dai et al., 2013; Prabhune and Dey, 2023; Stanisz et al., 2024; Suthar, 2025). For example, a study on the extraction of anthocyanins from grape skin showed that a specific DES formulation achieved a higher extraction yield and resulted in an extract with greater antioxidant stability compared to conventional acidified ethanol, all while being biodegradable and non-toxic (Jeong et al., 2015; Bosiljkov et al., 2017; Foroutani et al., 2024). This demonstrates the potential of green solvents to not only reduce environmental impact but also, in some cases, enhance the quality and stability of the extracted bioactive compounds (Chemat et al., 2019b; Aduloju et al., 2023; Ferreira and Sarraguça, 2024).

Both temperature and extraction time significantly affect the yield and stability of bioactive compounds:

Higher temperatures can increase solubility, diffusion rates, and mass transfer, leading to improved extraction efficiency (Kuosmanen et al., 2003).

However, prolonged exposure to high temperatures may cause oxidative degradation of thermolabile compounds such as vitamin C, polyphenols, and essential oils (Awad et al., 2021).

For instance:

Flavonoids and phenolic acids exhibit enhanced extraction at moderate temperatures (40°C–60°C), but temperatures above 80°C may lead to degradation (Antony and Farid, 2022).

Terpenoids and alkaloids, which are more stable, can be extracted efficiently at higher temperatures (70°C–100°C) (Rasul, 2018).

Supercritical CO₂ extraction operates at relatively low temperatures, making it ideal for preserving heat-sensitive compounds while maintaining high efficiency (Wang et al., 2021).

The extraction duration also plays a crucial role in maximizing bioactive compound recovery (Belščak-Cvitanović and Komes, 2017). Extended extraction times can increase yield but may lead to oxidation, hydrolysis, or polymerization, altering the bioactivity of sensitive phytochemicals (Brglez Mojzer et al., 2016).

The pH of the extraction medium can influence solubility, ionization, and stability of bioactive compounds:

Acidic conditions (pH < 5) favor the extraction of anthocyanins and organic acids but may cause degradation of certain polyphenols (Friedman and Jürgens, 2000; Enaru et al., 2021).

Alkaline conditions (pH > 7) enhance the solubility of alkaloids but may degrade phenolic compounds (Yubin et al., 2014; Oreopoulou et al., 2019).

EAE enhances extraction efficiency by breaking down plant cell walls and releasing intracellular bioactives (Wijesinghe and Jeon, 2012):

Cellulases and pectinases degrade plant fiber matrices, facilitating the release of flavonoids and glycosides (Costa et al., 2020).

Proteases can help recover bioactive peptides from protein-rich plant materials (David Troncoso et al., 2022).

Hemicellulases improve the extraction of arabinoxylans and other polysaccharides (de Souza and Kawaguti, 2021).

EAE is particularly useful in the food and pharmaceutical industries, as it reduces the need for harsh solvents and improves bioavailability.

Reducing the particle size of plant material can enhance solvent penetration and increase surface area, improving extraction efficiency (Ameer et al., 2017). Various pretreatment techniques have been employed to optimize extraction:

Grinding and milling: Reduces particle size, enhancing mass transfer (Kratky and Jirout, 2011).

Freeze-drying: Preserves bioactive integrity while facilitating better solvent diffusion (Rezvankhah et al., 2020).

Microwave and ultrasound pretreatment: Improves cell wall disruption, leading to higher yields (Passos et al., 2015).

To maximize extraction efficiency, various optimization approaches have been explored:

Multistage extraction: Sequentially using different solvents to target multiple bioactive groups (Wen et al., 2020).

Solvent recycling and green extraction: Employing eco-friendly solvents and low-energy extraction methods to reduce environmental impact (Hessel et al., 2022).

Automated process control: Using real-time monitoring and AI-driven optimization to improve reproducibility and efficiency (Yingngam et al., 2024).

By understanding and optimizing these factors, researchers can significantly improve the yield, stability, and bioactivity of natural product extractions, leading to more effective pharmaceutical, nutraceutical, and functional food applications (Figure 2).

UAE employs high-frequency sound waves to create cavitation, which disrupts plant cell walls and facilitates the release of intracellular compounds (Islam et al., 2023). This method enhances the extraction efficiency of phenolics, flavonoids, and other bioactive molecules while reducing extraction time and solvent consumption (Lovrić et al., 2017; Anaya-Esparza et al., 2023; Demesa et al., 2024).

MAE uses microwave radiation to rapidly heat the solvent and plant matrix, increasing the diffusion of target compounds. This technique has been shown to improve the recovery of thermolabile bioactives and enhance antioxidant potential compared to conventional extraction methods (Kanitkar et al., 2011).

SFE, particularly with supercritical carbon dioxide (SC-CO₂), is effective for extracting non-polar compounds such as terpenoids and lipophilic antioxidants (Dashtian et al., 2024). The adjustable pressure and temperature conditions allow for selective extraction while reducing solvent residues in the final product (Herrero et al., 2010). These advanced techniques provide promising alternatives to conventional extraction methods, ensuring higher efficiency and improved bioactivity of natural product extracts (Khaw et al., 2017).

While advanced techniques like UAE and MAE are widely praised for their high efficiency and reduced processing times, it is crucial to recognize that their effectiveness is not universal and is highly parameter-dependent. A critical review of the literature reveals that direct comparisons can yield variable outcomes, highlighting that there is no single “best” method for all applications (Azwanida, 2015). This variability often stems from the sensitivity of these methods to processing parameters. For example, while moderate sonication power in UAE can enhance cell disruption, excessive power or prolonged exposure can generate free radicals, leading to the degradation of thermolabile compounds like certain flavonoids (Shirsath et al., 2012; Chemat et al., 2017). In such cases, the final extract may exhibit lower bioactivity than one obtained from a carefully optimized conventional method (Kumar et al., 2021). Similarly, the effectiveness of MAE is highly dependent on the dielectric properties of the solvent and the matrix (Camel, 2000; Vinatoru et al., 2017). Improper settings can cause uneven heating and “hot spots,” which can compromise compound integrity (Mandal et al., 2007; Chemat et al., 2020; Bhadange et al., 2024). Therefore, a more nuanced perspective is required. The selection of an advanced technique must be accompanied by rigorous optimization of its key parameters (e.g., power, temperature, time, solvent choice) tailored to the specific phytochemicals and plant matrix (Bezerra et al., 2008). Simply adopting an advanced method without this critical optimization does not guarantee a superior result (Figure 3; Table 1).

HPLC is a widely used analytical method for separating, identifying, and quantifying phytochemicals in plant extracts (Boligon and Athayde, 2014). It operates by passing a liquid mobile phase through a column packed with a stationary phase, where compounds interact based on their polarity and affinity (Žuvela et al., 2019). This technique is effective for detecting flavonoids, polyphenols, alkaloids, and glycosides (Wolfender, 2009; Yuan et al., 2019).

Application: Used extensively in pharmaceutical and nutraceutical industries for quality control and standardization of plant extracts (Choudhary and Sekhon, 2011).

Advantages: High resolution, sensitivity, and reproducibility.

Limitations: Requires extensive sample preparation and solvent use (Dong, 2013).

Gas Chromatography-Mass Spectrometry (GC-MS) is ideal for analyzing volatile and semi-volatile phytochemicals, such as essential oils, terpenoids, and fatty acids (Ye, 2009). It works by vaporizing a sample and passing it through a column where compounds are separated based on their volatility (Hubschmann, 2025). The separated compounds are then identified based on their mass-to-charge ratio (Xie et al., 2019).

Application: Used in essential oil profiling, fragrance analysis, and food quality testing (Song and Liu, 2018).

Advantages: High specificity, rapid analysis, and excellent compound identification (Hao et al., 2007).

Limitations: Not suitable for non-volatile or thermally unstable compounds (Kornilova et al., 2013; Beale et al., 2018).

NMR spectroscopy provides structural and compositional insights into phytochemicals by detecting the interactions of atomic nuclei with an external magnetic field (Gautam et al., 2025). Unlike chromatographic methods, NMR is non-destructive and provides a comprehensive overview of molecular structures (Cade-Menun, 2005).

Application: Used for metabolomics studies, structural elucidation, and complex mixture analysis (Letertre et al., 2020).

Advantages: No extensive sample preparation, provides detailed molecular information.

Limitations: High cost of equipment and expertise required for data interpretation (Marcone et al., 2013).

Fourier Transform Infrared (FTIR) spectroscopy identifies functional groups in phytochemicals based on their absorption of infrared light (Vijayalakshmi and Ravindhran, 2012). It provides molecular fingerprints that are useful in distinguishing different plant metabolites (Rebiai et al., 2022).

Application: Used for rapid quality control, authentication of herbal medicines, and detecting adulteration (Huck, 2015).

Advantages: Fast, cost-effective, and non-destructive (Kumari et al., 2018).

Limitations: Limited ability to distinguish structurally similar compounds (Baker et al., 2014).

Ultra-High-Performance Liquid Chromatography (UHPLC) is an advanced form of HPLC that operates under higher pressure, allowing for faster separation and improved resolution (Dong and Zhang, 2014). This technique is particularly beneficial for analyzing complex phytochemical mixtures and detecting minor bioactive constituents (Wu et al., 2013).

Application: Used in pharmaceutical analysis, high-throughput screening, and quality control of functional foods (Ahmed et al., 2023).

Advantages: Increased resolution, faster analysis time, and lower solvent consumption (Dong and Zhang, 2014).

Limitations: Higher instrument cost and maintenance requirements (Dong and Zhang, 2014).

These analytical techniques are essential for accurately profiling phytochemicals and ensuring the quality and efficacy of natural product extracts. The choice of method depends on the nature of the compounds being analyzed, as well as the intended application. By integrating multiple techniques, researchers can achieve a comprehensive understanding of phytochemical composition and bioactivity, leading to improved standardization in pharmaceuticals, nutraceuticals, and functional foods (Figure 4).

Achieving standardization in natural product extraction is challenging due to the inherent variability in plant materials, including differences in species, growing conditions, and harvesting times (Bandaranayake, 2006; Afshar et al., 2022). The same extraction method may yield different phytochemical profiles depending on these variables (Wong et al., 2022). Therefore, standardized protocols must be established to ensure batch-to-batch consistency.

Reproducibility Issues: Variability in raw materials affects extraction efficiency, necessitating strict control of processing parameters such as solvent type, temperature, and extraction time (Sridhar et al., 2022).

Optimization of Key Parameters: Developing standardized protocols for solvent concentration, pH, pressure, and extraction duration is critical to achieving reliable results (Risticevic et al., 2010).

Regulatory Compliance: The standardization of extraction methods is essential for meeting pharmaceutical and nutraceutical regulatory guidelines (e.g., FDA, EMA, WHO) (Hossain et al., 2022).

While many extraction techniques are effective in laboratory-scale studies, their industrial-scale implementation presents technical and economic challenges.

Equipment and Infrastructure Limitations: Large-scale extraction requires specialized equipment such as high-pressure supercritical CO₂ systems or industrial-scale ultrasonic reactors, which involve high capital investment (Duba and Fiori, 2019).

Energy and Solvent Consumption: Scaling up extraction processes can significantly increase energy consumption and solvent use, leading to higher production costs and potential environmental impact (Pai et al., 2022).

Process Efficiency and Yield Optimization: Industrial-scale extractions must be optimized to maximize yield while maintaining bioactivity, ensuring cost-effectiveness without compromising product quality (Yadav et al., 2024).

The environmental impact of large-scale extraction processes is a growing concern, particularly with the use of organic solvents and excessive energy consumption.

Green Extraction Technologies: Sustainable alternatives such as supercritical CO₂ extraction, pressurized liquid extraction, and enzymatic-assisted extraction are being explored to minimize solvent waste and energy use (Alexandre et al., 2018).

Solvent-Free and Low-Energy Approaches: Techniques like subcritical water extraction and membrane-based separation systems offer eco-friendly solutions for extracting bioactive compounds with minimal environmental impact (Mondal et al., 2025).

Waste Management and Byproduct Utilization: Developing methods to recycle solvents and utilize extraction byproducts in secondary applications (e.g., animal feed, fertilizers) can enhance the sustainability of extraction operations (Soh and Eckelman, 2016).

While significant progress has been made, several key gaps in the literature need to be addressed to advance the field. Future research should be prioritized in the following areas.

• Techno-Economic Analyses (TEA): Direct and rigorous cost-benefit analyses comparing advanced extraction techniques (e.g., SFE vs MAE for a specific high-value compound) are urgently needed (Feng et al., 2022). Such studies are critical for guiding industrial adoption and determining economic viability (Apostolakou et al., 2009).