Extraction of Ferulic Acid and Caffeic Acid with Ionic Liquids

The effects of experimental conditions on extraction of polyphenols from African Nutmeg peels using NADESs-UAE: a multifactorial modelling technique

Extraction of polyphenolic compounds from African nutmeg (Monodora myristica (Gaertn.)) peels using natural acidic deep eutectic solvents coupled to ultrasound-assisted extraction (NADESs-UAE) followed many factors at a time (MFAT) screening with response surface optimization was investigated. Fourteen different NADESs based on citric acid as hydrogen bond acceptor (HBA) were designed and tested. Sucrose, fructose, xylitol, glycerol, glycine, and glucose were used as hydrogen bond donors (HBDs). The responses studied are total phenolic compounds (TPC), total flavonoid compounds (TFC), and antioxidant activity (AA) based on cupric ion reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP). The UAE procedure was optimized with the most efficient NADES. Quadratic models produced satisfactory fitting of the experimental data regarding TPC (R2 = 0.9999, p < 0.0001), TFC (R2 = 0.9991, p < 0.0001), and AA- CUPRAC (R2 = 0.9988, p < 0.0001) and FRAP (R2 = 1.000, P < 0001). Ultrasound temperature 30°c, extraction time 5 min, solvent volume 25 ml, and solvent concentration 90% (v/v) were considered optimal conditions for the extraction models resulting in TPC 1290.9 ± 5.6 mg/g GAE db, TFC 2398.7 ± 23 µg/g QE db, CUPRAC 38.46 ± 0.4.4 µmol/g TE db, and FRAP 26.15 ± 0.11µmol/g TE db, respectively.

A Perspective on Missing Aspects in Ongoing Purification Research towards Melissa officinalis

Melissa officinalis L. is a medicinal plant used worldwide for ethno-medical purposes. Today, it is grown everywhere; while it is known to originate from Southern Europe, it is now found around the world, from North America to New Zealand. The biological properties of this medicinal plant are mainly related to its high content of phytochemical (bioactive) compounds, such as flavonoids, polyphenolic compounds, aldehydes, glycosides and terpenes, among many other groups of substances. Among the main biological activities associated with this plant are antimicrobial activity (against fungi and bacteria), and antispasmodic, antioxidant and insomnia properties. Today, this plant is still used by society (as a natural medicine) to alleviate many other illnesses and symptoms. Therefore, in this perspective, we provide an update on the phytochemical profiling analysis of this plant, as well as the relationships of specific biological and pharmacological effects of specific phytochemicals. Currently, among the organic solvents, ethanol reveals the highest effectiveness for the solvent extraction of precious components (mainly rosmarinic acid). Additionally, our attention is devoted to current developments in the extraction and fractionation of the phytochemicals of M. officinalis, highlighting the ongoing progress of the main strategies that the research community has employed. Finally, after analyzing the literature, we suggest potential perspectives in the field of sustainable extraction and purification of the phytochemical present in the plant. For instance, some research gaps concern the application of cavitation-assisted extraction processes, which can effectively enhance mass transfer while reducing the particle size of the extracted material in situ. Meanwhile, membrane-assisted processes could be useful in the fractionation and purification of obtained extracts. On the other hand, further studies should include the application of ionic liquids and deep eutectic solvents (DES), including DESs of natural origin (NADES) and hydrophobic DESs (hDES), as extraction or fractionating solvents, along with new possibilities for effective extraction related to DESs formed in situ, assisted by mechanical mixing (mechanochemistry-based approach).

Extraction of Gallic Acid and Ferulic Acid for Application in Hair Supplements

Food supplements based on antioxidants and vitamins are often prescribed to correct inefficiencies in the human diet and delay diseases such as premature aging and alopecia (temporary or permanent hair loss), given the free radical scavenging activity of these biomolecules. By reducing the concentration of reactive oxygen species (ROS), which promote abnormal hair follicle cycling and morphology, follicle inflammation and oxidative stress are reduced, minimising the effects of these health issues. Gallic acid (GA), which is significantly present in gallnuts and in pomegranate root bark, and ferulic acid (FA), commonly found in brown rice and coffee seeds, are very important antioxidants for the preservation of hair colour, strength and growth. In this work, these two secondary phenolic metabolites were successfully extracted in the Aqueous Two-Phase Systems (ATPS) {ethyl lactate (1) + trisodium citrate (2) + water (3)} and {ethyl lactate (1) + tripotassium citrate (2) + water (3)} at 298.15 K and 0.1 MPa, moving towards the application of these ternary systems in extracting antioxidants from biowaste and their a posteriori processing as food supplements for hair fortification. The studied ATPS provided biocompatible and sustainable media for the extraction of gallic acid and ferulic acid, yielding low mass losses (<3%) and contributing to an eco-friendlier production of therapeutics. The most promising results were obtained for ferulic acid, which attained maximum partition coefficients (K) of 15 ± 5 and (3 ± 2) · 10¹ and maximum extraction efficiencies (E) of (92.7 ± 0.4)% and (96.7 ± 0.4)% for the longest tie-lines (TLL = 69.68 and 77.66 m%) in {ethyl lactate (1) + trisodium citrate (2) + water (3)} and {ethyl lactate (1) + tripotassium citrate (2) + water (3)}, respectively. Moreover, the effect of pH on the UV-Vis absorbance spectra was studied for all the biomolecules to minimise errors in solute quantification. Both GA and FA were found to be stable at the used extractive conditions.

Determination of Ferulic Acid in Angelica sinensis by Temperature-Controlled Hydrophobic Ionic Liquids-Based Ultrasound/Heating-Assisted Extraction Coupled with High Performance Liquid Chromatography

Hydrophilic ionic liquids are often used to extract the active ingredients of medicinal plants, while hydrophobic ionic liquids are rarely used to directly extract solid samples. In this paper, a simple, novel and efficient temperature-controlled hydrophobic ionic liquids-based ultrasound/heating-assisted extraction (TC-ILs-UHAE) procedure coupled with high-performance liquid chromatography (HPLC) was developed and applied to the determination of ferulic acid (FA) in Chinese herbal medicine Angelica sinensis. During the extraction procedure, hydrophobic ionic liquids (ILs) were dispersed into water to form cloudy solution (fine droplets) with the aid of ultrasound and heating simultaneous. After extraction, phase separation was easily achieved by centrifuging at 0 °C. Among all ILs used, 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide ([C₄mim]NTf₂) exhibited the highest extraction ability and the possible extraction mechanism was discussed. Additionally, the synergistic effect of heating and ultrasound on the extraction efficiency was investigated. Under the optimized conditions, a good linearity was observed with correlation coefficient (r) of 0.9995. The limit of detection of FA (LOD, S/N = 3) was 9.6 µg/L and the spiked recoveries of FA for real samples were in the range of 91.67 to 102.00% with relative standard deviation (RSD) lower than 3.87%. Compared with the traditional extraction methods, the proposed method gave the highest yield of FA and had the shortest extraction time. Therefore, this method is a potential simple, green and highly efficient technique and expected to be applied to the extraction of other bioactive ingredients in medicinal plants.

Advances and Prospects of Phenolic Acids Production, Biorefinery and Analysis

Biotechnological production of phenolic acids is attracting increased interest due to their superior antioxidant activity, as well as other antimicrobial, dietary, and health benefits. As secondary metabolites, primarily found in plants and fungi, they are effective free radical scavengers due to the phenolic group available in their structure. Therefore, phenolic acids are widely utilised by pharmaceutical, food, cosmetic, and chemical industries. A demand for phenolic acids is mostly satisfied by utilising chemically synthesised compounds, with only a low quantity obtained from natural sources. As an alternative to chemical synthesis, environmentally friendly bio-based technologies are necessary for development in large-scale production. One of the most promising sustainable technologies is the utilisation of microbial cell factories for biosynthesis of phenolic acids. In this paper, we perform a systematic comparison of the best known natural sources of phenolic acids. The advances and prospects in the development of microbial cell factories for biosynthesis of these bioactive compounds are discussed in more detail. A special consideration is given to the modern production methods and analytics of phenolic acids.

Ionic liquid-based microwave-assisted extraction of Heneicos-1-ene from coriander foliage and optimizing yield parameters by response surface methodology

In this study, an efficient ionic liquid (IL)-based microwave-assisted extraction (IL-MAE) was employed for the extraction of Heneicos-1-ene from coriander foliage. Quantification of Heneicos-1-ene was carried out using high-performance liquid chromatography. Parameters affecting extraction such as material to solvent ratio (1:10, 1:15, and 1:20), types of IL ([CH₃(CH₂)₃]₄NF, [BMIM][PF₆], [BMIM][BF₄], and [C₆H₅]₄P[Br]), concentration of IL (0.1, 0.5, and 1.0 M), microwave power (200, 500, and 800 W), extraction temperature (50, 70, and 90 °C) and extraction time (2, 6, and 10 min) were evaluated. Response surface methodology was applied to determine the optimum levels of these parameters to get maximum yield. The optimal conditions were achieved at 800 W, 90 °C for 2 min at a material to solvent ratio of 1:10 using 0.1 M solution of [BMIM][BF₄], to get maximum predicted yield of Heneicos-1-ene (412.8 mg/100 g) as against 408.5 ± 1.14 mg/100 g for experimental value with 0.991 correlation coefficient. IL-MAE resulted in 5.85 times higher yield as compared to the conventional method (69.77 ± 1.8 mg/100 g).

Identification of Six Phytochemical Compounds from Asparagus officinalis L. Root Cultivars from New Zealand and China Using UAE-SPE-UPLC-MS/MS: Effects of Extracts on H₂O₂-Induced Oxidative Stress

A simple, rapid, specific, and sensitive method was developed for the simultaneous identification and quantification of six major bioactive compounds, namely, caffeic acid, quercetin, apigenin, ferulic acid, baicalein, and kaempferol, from Asparagus officinalis roots (ARs) native to New Zealand (green and purple cultivars) and China (yellow, green, purple, and white cultivars) using ultrasound-assisted, solid-phase extraction (UASE-SPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The method was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy (expressed as recovery %), and precision (expressed as relative standard deviation (%RSD)). The retention times, ultraviolet visible (UV-vis) data, and mass spectral patterns of the detected peaks matched those of commercial standards, allowing characterization of the target compounds. The LODs and LOQs were 23 ng/mL and 70 ng/mL, 50 ng/mL and 150 ng/mL, 10 ng/mL and 30 ng/mL, 18 ng/mL and 54 ng/mL, 14.4 ng/mL and 43.6 ng/mL, and 7.5 ng/mL and 22.5 ng/mL for caffeic acid, quercetin, apigenin, ferulic acid, baicalein, and kaempferol, respectively, and the mean recovery rates were 85.8%, 73.0%, 90.2%, 80.6%, 76.7%, and 74.5% for the six compounds, respectively. The levels of the target compounds were significantly different (p < 0.05) among the six cultivars. The Chinese yellow AR had the highest levels of bioactive compounds: 6.0, 3.9, 0.4, 1.0, 0.86, and 0.8 mg/g for caffeic acid, quercetin, apigenin, ferulic acid, baicalein, and kaempferol, respectively. The AR extracts showed protective effects against oxidative stress in the HepG2 and L929 cell lines. The results indicate that AR extracts contain high flavonoid levels that provide protective functions against oxidative stress and support the potential commercial application of AR extracts.

Influence of ionic liquid on Novozym 435-catalyzed the transesterification of castor oil and ethyl caffeate

Caffeic acid (CA), one kind of phenolic acids widely occurring in the plant kingdom, can be used as potential UV protective ingredient and antioxidant. However, the application of CA was limited because of its unsatisfactory solubility in hydrophilic and lipophilic media. In this work, BMIMPF₆, one kind of ionic liquids (ILs), was developed as an environmental friendly reaction media for the enzymatic preparation of CA derivatives by the transesterification of castor oil (CO) and ethyl caffeate (EC). Different series of ILs with BF 4 - , TF 2 - , and PF 6 - were screened and compared, and the effects of transesterification variables [temperature (60-100 °C) enzyme concentration (10-90 mg/mL), substrate molar ratio (CO/EC, 1:1-5:1), water load (0-8%), and reaction pressure] were also investigated. Results showed that, in the IL system, hydrophilic and lipophilic products were formed by two competitive reactions [(i) hydrolysis + transesterification and (ii) transesterification]. The maximum hydrophilic caffeoyl lipids yield (26.10 ± 0.28%) and reaction selectivity for hydrophilic caffeoyl lipids (0.4) was achieved in BMIMPF₆ system. The increases of substrate ratio (molar ratio of CO to EC, from 1:1 to 5:1), water load (from 0 to 8%), and enzyme concentration (from 10 to 90 mg/mL) were in favor of hydrophilic caffeoyl lipid formation. However, the vacuum system and high temperature (from 70 to 100 °C) are favorable for lipophilic caffeoyl lipids formation. Under the optimal reaction conditions (90 °C, 75 mg/mL enzyme concentration, substrate ratio 3:1, 60 h, and 10 mmHg vacuum pressures), the maximum EC conversion was 72.48 ± 2.67%. The activation energies of the transesterification, and the selective formations of lipophilic and hydrophilic products were calculated as 44.55, 47.65, and 54.96 kJ/mol, respectively.

Ultrasound-Assisted, Base-Catalyzed, Homogeneous Reaction for Ferulic Acid Production from γ-Oryzanol

A method for producing ferulic acid by ultrasound-assisted, homogeneous, base-catalyzed hydrolysis of γ-oryzanol was developed. Experiments were conducted using various reaction temperatures and ratios of γ-oryzanol to base catalyst in both homogeneous and heterogeneous systems. The reaction performed without ultrasound under the homogeneous conditions of potassium hydroxide/γ-oryzanol ratio (wt/wt) 20 : 1 and 75°C gave a ferulic acid yield of 83.3% in 3 h. Acceleration of the homogeneous reaction using ultrasound irradiation at 20 (horn type) and 200 kHz (planar type) was explored by evaluating the kinetic parameters. At 30°C, the ratios of ultrasonic irradiation at low (20 kHz, 50 W) and high (200 kHz, 50 W) frequencies versus those of the heating method increased by 2.0- and 1.4-fold in comparison with those at 60°C, respectively. The contribution of ultrasonic irradiation (50 W) to the hydrolysis reaction decreased with increase of temperature. However, irradiation at 20 kHz and a power of 180 W gave a 94% ferulic acid yield at 60°C in 3 h. These results indicate that the use of low frequency (horn type and high-power irradiation) enabled yields higher than 90% to be obtained.

Ionic liquids and deep eutectic solvents in natural products research: mixtures of solids as extraction solvents

Mixtures of solid chemicals may become liquid under certain conditions. These liquids are characterized by the formation of strong ionic (ionic liquids) or hydrogen bonds (deep eutectic solvents). Due to their extremely low vapor pressure, they are now widely used in polymer chemistry and synthetic organic chemistry, yet little attention has been paid to their use as extraction solvents of natural products. This review summarizes the preparation of ionic liquids and deep eutectic solvents with natural product components and recent progress in their applications to the extraction and analysis of natural products as well as the recovery of extracted compounds from their extracts. Additionally, various factors affecting extraction features of ionic liquids and deep eutectic solvents, as well as potential useful technologies including microwave and ultrasound to increase the extraction efficiency, are discussed.

Correlating the structure and composition of ionic liquids with their toxicity on Vibrio fischeri: A systematic study

A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a bioluminescent marine bacteria generally used in ecotoxicological bioassays, was carried out. The objectives of this work were to find hydrophilic or hydrophobic low toxicity IL and to investigate structure-toxicity relationship of IL. Toxicity of 54 IL to V. fischeri have been measured, some referring to new IL based on quinuclidinol or tropinol and some to generic IL (i.e., imidazolium, pyridinium, pyrrolidinium or piperidinium). For 47 of them, toxicity values have not been reported elsewhere. Water-soluble IL containing hydrophilic anions halide, thiocyanate, dicyanamide, trifluoromethansulfonate were studied. Some IL were found to exhibit very low toxicity towards V. fisheri. Hydrophobic IL based on bis(trifluoromethanesulfonyl)imide, tetrafluoroborate tetraphenylborate and tetracyanoborate were also studied. Toxicity was measured in a consistent way starting from aqueous solutions saturated with IL. The least toxic hydrophobic IL found in this study was [EMIM][B(CN)(4)]. A multifactorial analysis was found to be convenient for finding relevant structure parameters influencing the toxicity of IL. From this analysis, the planarity of the cation ring appeared to be a relevant parameter. Finally, good linear correlations were found when toxicity of IL was plotted either against the number of aliphatic carbons surrounding a pyridinium cation or the total number of carbons of a cation.

Effect of ionic liquids on enzymatic synthesis of caffeic acid phenethyl ester

Although caffeic acid phenethyl ester (CAPE), an active flavonoid, plays an important role in the antioxidant activity of honeybee propolis, the isolation of CAPE from honeybee propolis is time-consuming due to wide variety of impurities present. Therefore, biochemical method to synthesize CAPE was investigated in this study. Since ionic liquids (ILs) possess some unique characteristics as appreciated alternatives to conventional solvents for certain biotransformation, the effect of ILs as reaction media for enzymatic synthesis of CAPE was assessed. Several factors including substrate molar ratio, and reaction temperature affecting the conversion yield of lipase-catalyzed CAPE synthesis were also investigated. Reaction yields were significantly higher in hydrophobic ILs than in hydrophilic ILs (almost zero). Among nine hydrophobic ILs tested, the highest conversion of synthetic reaction was obtained in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Emim][Tf(2)N]). A reaction temperature of 70 °C was found to give high conversion. In addition, optimal substrate molar ratio between phenethyl alcohol and caffeic acid (CA) was decreased significantly from 92:1 to 30:1 when ILs were used instead of isooctane.

Recent applications of ionic liquids in separation technology

Ionic liquids (ILs) have been applied in different areas of separation, such as ionic liquid supported membranes, as mobile phase additives and surface-bonded stationary phases in chromatography separations and as the extraction solvent in sample preparations, because they can be composed from various cations and anions that change the properties and phase behavior of liquids. Although the applications of ILs in separations are still in their early stages, the academic interest in ILs is increasing. An overview of the principle applications of ILs in separation technology is present in this work. Furthermore, the prospects of the ILs in separation techniques are discussed.