Microwave-assisted Extraction Of Phenolic Compounds Research Articles

Microwave-assisted extraction of phenolic compounds from Commiphora gileadensis leaf and their characterization

Commiphora gileadensis (C. gileadensis) is a plant traditionally used in many parts of the world for medicinal purposes. However, the benefits of this plant are yet to be uncovered due to the use of conventional extraction methods during its extraction. Hence, there is a need for more efficient and environment-friendly extraction methods for optimum recovery of the bioactive components of C. gileadensis. This study aims to evaluate the impact of microwave-assisted extraction (MAE) process parameters (individually and in combination) on the recovery of phenolic compounds from C. gileadensis leaf. One-Factor-At-a-Time (OFAT) optimization method was used in this work to study the impact of varying the MAE process parameters (sample: solvent ratio, microwave power, ethanol concentration, and extraction temperature) on the optimum yield of phenolic compounds. The obtained phenolic compounds were characterized using Gas chromatography-mass spectrometry (GC–MS) for tentative identification of the component phytochemicals of the extract. The results showed that the optimal process condition of microwave power at 300 W, solvent/sample ratio of 1:10 g/mL, solvent concentration of 40 % v/v, and extraction temperature of 40 °C gave the maximum extraction yield of 33.20 ± 0.42 % w/w, total phenolic content (TPC) of 114.65 ± 3.14 mg GAE/g d.w., and total flavonoids content (TFC) of 37.56 mg QE/g d.w.). Furthermore, the GC-MS analysis identified 25 phenolic compounds with good antioxidant activities from the extracts. Therefore, MAE is considered a non-conventional green method for improved extraction of phenolic compounds from C. gileadensis leaf compared to the existing conventional extraction methods.

Microwave-Assisted Extraction of Phenolic Compounds and Antioxidants for Cosmetic Applications Using Polyol-Based Technology.

The utilization of polyols as green solvents for extracting bioactive compounds from plant materials has gained attention due to their safety and inert behavior with plant bioactive chemicals. This study explores the sustainable extraction of phenolic compounds and natural antioxidants from coffee silverskin using the microwave-assisted extraction (MAE) method with polyol-based solvents: glycerin, propylene glycol (PG), butylene glycol (BG), methylpropanediol (MPD), isopentyldiol (IPD), pentylene glycol, 1,2-hexanediol, and hexylene glycol (HG). A comparative analysis was conducted on conventional and non-conventional solvent extractions, focusing on their impact on the bioactive compounds of MAE, encompassing parameters such as total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities like the 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay (DPPH), the 2,2'-azino-bis(-3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging assay (ABTS), and the ferric reducing antioxidant power assay (FRAP). The highest values were observed for TPC with aqueous-1,2-hexanediol extraction (52.0 ± 3.0 mg GAE/g sample), TFC with aqueous-1,2-hexanediol extraction (20.0 ± 1.7 mg QE/g sample), DPPH with aqueous-HGextraction (13.6 ± 0.3 mg TE/g sample), ABTS with aqueous-pentylene glycol extraction (8.2 ± 0.1 mg TE/g sample), and FRAP with aqueous-HG extraction (21.1 ± 1.3 mg Fe (II) E/g sample). This research aims to advance eco-friendly extraction technology through natural plant components, promoting sustainability by minimizing hazardous chemical use while reducing time and energy consumption, with potential applications in cosmetics.

Understanding microwave-assisted extraction of phenolic compounds from diverse food waste feedstocks

Microwave-assisted extraction (MAE) of natural antioxidants from food waste (FW) offers an economically appealing waste management strategy. However, MAE from mixed FW has received limited attention. We characterize five single waste streams (apple, coffee, olive, tomato, and potato peel waste) and study MAE of phenolic acids from select feedstocks and mixtures. This library of materials enables us to unravel the relationship of FW composition and physical properties with dielectric properties, heating, and extractive yields. Protein, ash, and moisture contents affect dielectric properties the most. Our study unveils the significance of moisture in free (> 20 wt%) and bound states (< 20 wt%) on FW dielectric properties, heating, and target acid yields (at least 33 % enhancement). Microwaves primarily heat the solvent (dimethylformamide) due to its superior dielectric properties compared to FW (dry and moist, single and mixtures) at ≤ 0.05 solid-to-liquid ratio (g/mL). High moisture content (> 20 wt%) provides higher phenolic yields at lower temperatures (< 100 °C) and shorter times (≤ 10 min) due to enhanced heat and mass transfer by microwaves. Further, our data indicates significant interactions between mixed FW components that drive 2–3x higher yields than those predicted from a simple additive model from single component results. Our work provides new insights for developing versatile MAE strategies to treat mixed FW feedstocks.

Optimization of microwave-assisted extraction of phenolic compounds and antioxidants from Careya sphaerica Roxb. flowers using response surface methodology

Careya sphaerica Roxb. flowers are good sources of phenolic compounds (PCs) with bioactive properties such as antioxidant activity. The objective of this study was to optimize the extraction parameters for microwave-assisted extraction (MAE) of PCs from C. sphaerica Roxb. flowers, utilizing response surface methodology (RSM) through a central composite design. The extraction of PCs was significantly (p < 0.05) impacted by process variables. The best possible combinations were microwave power (MP) 1000 W, solid to solvent (S-S) ratio 1:100 g: mL, ethanol concentration 40 % v/v, and extraction time 20 s to obtain the maximum extraction yield (EY), extractable phenolic compounds (EPC), DPPH and total flavonoid content (TFC). The maximum EY, EPC, DPPH, and TFC of 70.4 g, 33,504 mg GAE, 24,355 mg GAE and 13,115 mg CE, respectively were obtained per 100 g dry mass. The result suggests that MP and S-S ratio significantly (p < 0.05) affect the extraction of PCs and DPPH. All of the models applied to fit the responses were significant (p < 0.01) and suitable to represent the relationship between independent variables and responses. The study revealed the effectiveness of MAE using RSM for the extraction of PCs from C. sphaerica flowers.

Microwave-Assisted Extraction of Phenolic Compounds from Smilax ovalifolia Roxb. and Chemical Compositions

Smilax ovalifolia Roxb. is a medicinal herb in southern Thailand. However, there are not many studies on active compounds from this plant. This study aimed to optimize extraction conditions for total phenolic content (TPC) from S. ovalifolia root using microwave-assisted extraction (MAE) and to determine the phytochemical compositions and antioxidant activity of the extract. The result showed that the optimal conditions of phenolic compounds extraction include ethanol concentration of 85% v/v, a solid-to-solvent ratio of 1:30 (g/mL), microwave power of 450 W, and extraction time of 150 s. The phenolic-rich extract exhibited strong antioxidant activity with IC50 of 6.31 ± 0.05 mg/mL. LC-MS was used to fingerprint analysis of the extract. The result revealed the presence of 18 bioactive compounds. The main components of S. ovalifolia root extract were some flavonoids, including catechin, epicatechin, procyanidin B2, and quercetin.

Simulation and experimentation on parameters influencing microwave-assisted extraction of bioactive compounds from Punica granatum waste and its preliminary analysis

Nowadays, the revalorization of high-value components of waste is the business goal for the development of food supplements in personalized nutrition, pharmaceuticals, and cosmetics. The objective of this study was to simulate and upgrade the extract quality of the medicinal plant Punica granatum L. peel powder by using microwave-assisted extraction (MAE). The central composite design was implemented for optimized parameters ethanol concentration of (50%), solvent: solid ratio (25:1 mL/g), extraction time (4 min), microwave power (450 W), on yield of 47.3%, total phenolic content of 432.05 mg GAE/g, DPPH reduction of 87.34%, was observed. The extract obtained after MAE of phenolic compounds contained 279.2 mg TAE/g DM of the highest total ellagitannin content and 25 mg QE/g DM of the flavonoid content of pomegranate peel powder. The structural characterization of bioactive compounds before and after MAE was performed using FTIR, SEM, and XRD. FT-IR technique was used to identify the functional groups in the pomegranate peel extract. The highest antioxidant active rich pomegranate peel extract proved that it can be utilized for the preparation of functional foods. This ‘green technology’ can be applied to various by-product processing and can be useful for upgrade studies for the value-addition of food products using an extraction approach. Practical applicationsThis study aims to establish a sustainable prototype for agro-industrial wastage management using an approach to process pomegranate peel that can deliver better economic and environmental outcomes. In this case, the application of the pomegranate peel extract is presented as an alternative to synthetic preservatives due to its highest antioxidant capacity. The advantage of the MAE procedure was the higher yield of up to 50% of extract per gram of peel powder. Our study demonstrates that statistically designed experiments allow for significant enhancement of the extraction process, which application could aid better use of natural resources and deliver more potent extracts than those obtained by currently recommended procedures.

Optimization of microwave-assisted extraction of phenolic compounds from chestnut processing waste using response surface methodology

Portugal is one of the world's top ten chestnut producers. The nut shells generated in the industrial processing have been discarded for use as soil conditioner or energy production. This waste material is rich in polyphenols, which can be used for various purposes, including well-established applications and new usages. Tannin-based coagulants/flocculants for water treatment are one of the emerging applications. Polyphenols extraction from vegetal sources is the initial step of the coagulant synthesis. In this work, tannin extraction from chestnut shell was accomplished in aqueous solution through different methods. After a preliminary assessment, microwave-assisted method (MAE) was selected to be optimized using Response Surface Methodology. The effect of extraction time, liquid:solid ratio, and temperature on the extraction yield and total phenolic content of the extracts was examined. The desirability function approach was applied to find the best extraction conditions leading to a quantitative extract with the highest phenolic content. The optimum conditions were determined as extraction time of 5 min, liquid-to-solid ratio of 50 mL g−1 and temperature 107 °C. In these optimized conditions, the expected extraction yield and phenolic content of the extract are 25 ± 3% and 344 ± 27 mg-GAE/g, respectively (values confirmed by experimental assays). The optimal extract presented a condensed tannin content of 1296 ± 68 mg-CE/g. This work showed that polyphenols can be quantitatively extracted from chestnut shells through a green approach and the generated extract has good features to be further used as a raw material for water treatment coagulants.

Microwave-Assisted Extraction of Phenolic Compounds from Pineapple Peel Using Deep Eutectic Solvents

Approximately half of the world’s pineapple production is marketed as a processed product, leading to the generation of a significant quantity of industrial waste, mainly composed of pineapple peels, cores, and crowns. This study evaluated deep eutectic solvents (DESs) for the assisted microwave extraction of phenolic compounds from pineapple peels and their antioxidant capacity. DESs are considered environmentally friendly solvents characterized by their low toxicity and high capacity for the extraction of bioactive compounds. DESs (choline chloride-glycerol and choline-chloride-malic acid) were used for phenolic compound extraction and compared with traditional solvents such as water, ethanol, methanol, ethanol-water (50%), and methanol-water (50%). A higher concentration of phenolic compounds was achieved using choline chloride-glycerol than traditional solvents as an extraction solvent (7.98 mg eq of gallic acid/g of dry weight). In all the treatments, the antioxidant capacity was higher than 85%. The process variables (drying temperature, extraction time, and solvent/solid ratio) were optimized using choline chloride-glycerol as a solvent. It was found that a drying temperature of 67 °C, an extraction time of 87 s, and a solvent/solid ratio of 60.5 mL/g allow maximizing the content of phenolic compounds and the antioxidant capacity of the extract.

Optimization of microwave-assisted extraction of phenolic compounds from Inula britannica L. using the Box-Behnken design

A closed-vessel microwave-assisted extraction (MAE) of phenolic compounds from the aerial parts of Inula britannica L. using single-factor experiments and the Box-Behnken design with four independent variables (liquid-to-solid ratio, ethanol concentration, extraction time, and temperature) was investigated. The ANOVA results showed that the obtained model was significant at a 95 % confidence level. The extraction parameters for the maximal total phenolic content (46.19 mg GAE/g DM) were determined to be 15.13 ml/g liquid-to-solid ratio, 55.95 % EtOH, 73.74 ºC, and 5.73 min. Compared with classical maceration, the proposed MAE of phenolic compounds from I. britannica saves a lot of time and gives a high extraction yield.

Microwave-Assisted Extraction of Phenolic Compounds from Broccoli (Brassica oleracea) Stems, Leaves, and Florets: Optimization, Characterization, and Comparison with Maceration Extraction

Microwave-assisted extraction (MAE) to obtain phenolics from vegetable wastes has been of recent interest. Broccoli is one of the most globally produced vegetables, and around 43% of the harvest is considered waste. Thus, given the significant quantity of broccoli waste generated, the objective of this work was to optimize the MAE, to maximize the total phenolic content (TPC) from broccoli by-products (leaves and stems) and broccoli florets. The Response Surface Analysis was used in the optimization model to evaluate the impacts of methanol concentration, time, and temperature, and their interactions on the TPC of the broccoli extracts. The optimal MAE conditions were found to be 74.54% (methanol), 15.9 min, and 74.45 °C for broccoli stems; 80% (methanol), 10 min, and 73.27 °C for broccoli leaves; and 80% (methanol), 18.9 min, and 75 °C for broccoli florets. Under these conditions, the broccoli leaves exhibited the highest TPC (1940.35 ± 0.794 µg GAE/g DW), followed by the florets (657.062 ± 0.771 µg GAE/g DW) and stems (225.273 ± 0.897 µg GAE/g DW). The antioxidant activity of the broccoli extracts was evaluated under the optimal conditions by DPPH and ABTS assays, and the same behavior was observed in both studies, the broccoli leaves exhibited the highest antioxidant activity, among florets and stems. In addition, vanillic, sinapic, caffeic, chlorogenic, ferulic, gallic, neochlorogenic, and p-coumaric acids in the broccoli extracts were identified and quantified using HPLC. Furthermore, MAE was found to increase the phenolic yield up to 45.70% for broccoli leaves, 133.57% for broccoli florets, and 65.30% for broccoli stems, in less time compared with maceration extraction. MAE proved to be an efficient and sustainable technique to obtain phenolics from broccoli by-products, which can constitute a viable solution for valorizing broccoli wastes.

Microwave-Assisted Extraction of Phenolic Compounds from Spent Coffee Grounds. Process Optimization Applying Design of Experiments.

In this study, sustainable technology microwave-assisted extraction (MAE) in association with green solvents was applied to recover phenolic compounds from spent coffee grounds (SCGs). A design of experiments (DOE) was used for process optimization. Initially, a 24−1 two level Fractional Factorial Design was used and ratios “solvent to solute” and “ethanol to water” were identified as the significant experimental factors. Consequently, Central Composite Design (CCD) was applied to analyze the effects of the significant variables on the response yield, total polyphenols content (TPC), and antioxidant activity (AA) by the DPPH assay method, and quadratic surfaces to optimize those responses were generated. The values of the significant factors of 16.7 (solvent/solute) and 68.9% (ethanol/water) were optimized simultaneously the yield (%) at 6.98 ± 0.27, TPC (mg GAE/g) at 117.7 ± 6.1, and AA (µmol TE/g) at 143.8 ± 8.6 and were in excellent agreement with those predicted from the CCD model. The variations of the compositions of the lipids, caffeine, pentacyclic diterpenes, and FAME as a function of the dominant factor % ethanol in the solvent mixture were analyzed by applying NMR and GC-FID, and the results obtained confirmed their determinative significance.

Microwave-assisted extraction of phenolic compounds from coffee (Coffea robusta L. Linden) bee pollen

Summary Introduction: Coffee bee pollen contains some precious bioactive compounds, especially phenolic compounds. This material is easily found in many regions in Vietnam and is quite useful for human health. Objective: The main aim of this study was to determine the best extraction conditions for the total polyphenol content (TPC) and antioxidant capacity (AC) of coffee (Coffea robusta L. Linden) bee pollen with microwave-assisted extraction (MAE). Methods: TPC and AC of extract of coffee (C. robusta) bee pollen were determined using Folin-Ciocalteu (FC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. In addition, micromorphology of sample was observed using scanning electron micrographs (SEM). Results: The findings showed that all factors strongly affected the efficiency of the extraction process. The best extraction conditions obtained were ethanol concentration of 60% (v/v), solid to solvent ratio of 1/30 (w/v), extraction time of 7 min, and a microwave power of 314 W. Conclusion: The highest TPC and AC obtained were 13.73 mg GAE/g DW and 10.08 µmol TE/g DW with aqueous ethanol as the solvent at the optimal extraction condition. In addition, the microstructures of the material changed insignificantly under microwave irradiation.

Microwave-assisted extraction of phenolic compounds from Carica papaya leaves: An optimization study and LC-QTOF-MS analysis

Carica papaya is a well-known plant with diverse importance to human beings. The efficacy of microwave-assisted extraction (MAE) in the recovery of phenolic compounds from C. papaya leaf was investigated in this study. The MAE process variables were optimized using response surface method; at the optimized conditions, the embedded phenolic compounds in the extract were identified through LC-QTOF-MS analysis. The results showed that the best MAE conditions were: time of irradiation at 3 min; microwave power of 420 W; feed-to-solvent ratio of 1:12 g/mL; and solvent concentration of 56% ethanol/water to achieve 102.59 mg GAE/g d.w. of total phenolic content (TPC). At these conditions, an aggregate of 72 phenolic compounds was tentatively identified. These results infer that MAE as a technique can recover phenolic compounds from C. papaya leaf. Hence, the identified compounds can further be quantified with their respective pharmacological properties in future studies.

Optimization of microwave-assisted extraction of phenolic compounds from tomato: Characterization by FTIR and HPLC and comparison with conventional solvent extraction

In the extraction of phenolic compounds from tomato, Microwave-Assisted Extraction (MAE) was used as a novel technology in this study and compared to conventional solvent extraction (CSE). The optimal extraction conditions for tomato were determined using the multi-level factorial design. For this purpose, different powers (360, 600 and 900 W) and times (30, 60 and 90 s) were used for MAE and also different temperatures (40, 50 and 60 °C) and times (10, 20 and 30 min) were used for CSE. Total phenolic content (TPC), antioxidant activity (AA), and morphological changes were measured by the Folin–Ciocalteu assay, DPPH-scavenging activity, scanning electron microscopy (SEM) respectively. Phenolic compounds of tomato extracts were determined by using Fourier transform infrared (FTIR) spectroscopy and high performance liquid chromatography (HPLC). According to the results, MAE increased TPC and AA compared to CSE. The highest TPC (436.20 ± 4.34 mg GAE/kg FW) and antioxidant activity (39.15 ± 0.91 % of DPPH inhibition) was observed for MAE at 900 W, 90 s which was related with morphological changes, determined by SEM. Multivariate analysis (PCA and PLS) were used to discriminate and construct chemometric models in order to predict AA or TPC of the extracts using IR spectra. The bands found in the FTIR spectrum were found to be associated with chlorogenic acid and ferulic acid. Furthermore, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid were quantified with HPLC. Chlorogenic acid was detected as the main phenolic compound in tomato extracts. The highest amount of chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid was found as 52.33 ± 0.80, 5.03 ± 0.37, 0.803 ± 0.017 and 0.506 ± 0.013 mg/kg FW, respectively with MAE at 900 w 90 s.

Optimization and Comparison of Ultrasound and Microwave-Assisted Extraction of Phenolic Compounds from Cotton-Lavender (Santolina chamaecyparissus L.)

The interest in natural phenolic compounds has increased because of their attractive use especially as antioxidant and antimicrobial agents in foods. The large content in phenolic compounds of interest in Santolina chamaecyparissus L. (S. chamaecyparissus) makes this plant a target source that is worthy of note. In this work, new extraction technologies comprising ultrasound (UAE) and microwave (MAE) assisted extraction of the phenolic compounds in S. chamaecyparissus have been developed, optimized, and compared. Several extraction factors have been optimized based on a Box-Behnken design. Such optimized factors include the percentage of methanol in water (25–75%), the temperature (10–70 °C), the ultrasound amplitude (20–80%), the ultrasound cycle (0.2–1 s), the solvent pH (2–7) and the solvent-sample ratio (5/0.2–15/0.2 mL/g) with regard to UAE, while the percentage of methanol in water (50–100%), the temperature (50–100 °C), the pH (2–7) and the solvent-sample ratio (5/0.2–15/0.2 mL/g) were optimized for MAE. The solvent composition was the most influential parameter both on MAEs (64%) and UAEs (74%). The extraction optimum time was established as 15 min for MAE and 25 min for UAE. Five major phenolic compounds were detected and identified by Ultra-High-Performance Liquid Chromatography—Quadrupole Time of Flight—Mass Spectrometry (UHPLC-QToF-MS) in the extracts: chlorogenic acid, quercetin 3-O-galactoside, quercetin 3-O-glucoside, isoorientin, and cynarin. With the exception of chlorogenic acid, the other four compounds have been identified for the first time in S. chamaecyparissus. The findings have confirmed that MAE is a significantly more efficient extraction method than UAE to extract phenolic compounds from S. chamaecyparissus.

Microwave-assisted extraction of phenolic compounds with antioxidant and anti-proliferative activities from supercritical CO2 pre-extracted mango peel as valorization strategy

This work includes the second/sequential stage of a green-based valorization strategy of mango peel. An exhausted biomass from a pilot-scale CO2 supercritical extraction process was reused for obtaining phenolic-rich extracts with high antioxidant and anti-proliferative activity, employing microwave-assisted extraction. The effects of microwave power (400–800 W), liquid-to-solid ratio (10–50 mL/g) and extraction time (60–120 s) on process yield, phenolic content, and antioxidant capacity were investigated using a Box-Behnken design. A solution consisting of 60% aqueous ethanol was used as extraction solvent. The results showed that microwave power and liquid-to-solid ratio were the most influential factors on the responses variables. The highest total phenolic content (52.08 mg gallic acid eq./g d. w.) and antioxidant activities (2.75 mmol trolox eq./g extract, and of 6.47 μg/mL expressed in DPPH, EC50) were obtained at 800 W, 50 g/mL, and 90 s. Mango peel extract recovered at optimal conditions provided high anti-proliferative activity against HT-29 colon cancer cells line, after 24 h treatment (IC50 = 22.98 μg/mL). Gallic acid derivatives, such as galloyl-esters, xanthones like mangiferin, flavonoids, including quercetin and quercetin glycosides were tentatively identified by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Most probably, the compounds responsible for the outstanding anti-proliferative activity.

Microwave-assisted extraction of phenolic compounds from Cannabis sativa L.: optimization and kinetics study

ABSTRACT RSM and ANN were evaluated for prediction of physical and chemical properties of industrial hemp extracts prepared using MAE. The effects of liquid to solid ratio, ethanol content, extraction time, extraction temperature, and microwave power were analyzed. ANN had better prediction performance for both physical and chemical properties. Optimal conditions based on RSM were L/S = 30 mL/g, v/v = 25%, t = 25 min, T = 45°C and P = 600 W. Under those conditions, dynamic of the extraction process was analyzed using six kinetic models and showed that the extraction rate reached constant value after approximately 15 min.

Optimization of microwave-assisted extraction of phenolic compounds from Ocimum gratissimum leaves and its LC–ESI–MS/MS profiling, antioxidant and antimicrobial activities

Phenolic compounds are essential for growth, pigmentation, resistance to pathogens, reproduction, and among others. This study focused on the optimization of microwave-assisted extraction process variables, i.e., solvent/sample ratio (X1), irradiation time (X2) and microwave power (X3), based on the yields of total phenolic content (TPC) and total flavonoid content (TFC) from Ocimum gratissimum leaf using Box Behnken Design. Furthermore, the chemical compounds in the extract under optimized MAE conditions were identified using LC–ESI–MS/MS analysis; its antioxidant and antibacterial properties were evaluated as well, and optimal MAE conditions, i.e., X1 = 10:1 mL/g, X2 = 3 min and X3 = 553 W, were obtained with TPC and TFC yields of 184.99 ± 3.05 (mg GAE/g extract) and 68.78 ± 2.07 (mg QE/g extract), respectively. The results indicated that the leaf extract of O. gratissimum possesses antioxidant and antibacterial properties. Aside from these, the LC–ESI–MS/MS analysis provided tentative identification of 131 phenolic and other phytochemical compounds in the leaf extract at optimized conditions. The extract showed higher inhibitory activities against all the considered bacteria organisms (at least the concentration of 15 mg/mL). Thus, O. gratissimum leaf can be employed as an industrial crop with potential usage in the nutraceutical and food products.

Microwave-assisted extraction of phenolic compounds from Euphorbia hirta leaf and characterization of its morphology and thermal stability

ABSTRACT This study succinctly investigated the impacts of energy-based functions on the total phenolic and physicochemical characteristics of Euphorbia hirta. The results of the orthogonal experimental array gave an optimum microwave condition at 2 min of irradiation time, 400 W of microwave power, 12 mL/g of solvent loading, 40°C of the temperature level, and 50% of ethanol concentration. The results from the thermal stability curves revealed initial 89.96% weight retention (< 100°C) from moisture loss and the potential formation of sixty-six phenolic constituents from the disorientated microstructure (<170°C). The above results established the satisfactory performance of the microwave-reflux extraction method.

Optimization of microwave-assisted extraction of phenolic compounds in Dendrobium formosum Roxb. ex Lindl. and glucose uptake activity

Phenolic compounds are active compounds in Dendrobium formosum Roxb. ex Lindl. that have antidiabetic and anti-obesity activities. To obtain a high extraction yield of phenolic compounds from D. formosum, optimization of microwave-assisted extraction (MAE) was developed in this study using response surface methodology. The optimal conditions for phenolic compound yield were using absolute ethanol as the solvent, 540 W of microwave power, 49.37 s of extraction time, a 22.67 mL/g solvent-to-feed ratio, and three extraction cycles. The yields of coelonin, erianthridin, moscatilin, lusianthridin, gigantol and batatasin III when extracted under optimal conditions were 0.38 ± 0.04, 0.40 ± 0.05, 1.45 ± 0.18, 0.14 ± 0.01, 0.47 ± 0.05 and 0.58 ± 0.06 mg/g dry weight, respectively, with errors of less than 4% deviation from the predicted values. Our results indicate that MAE can obtain a higher yield of phenolic compounds and have a greater effect on glucose uptake than those of other extraction methods. Therefore, MAE has high efficiency for extracting phenolic compounds from D. Fomosum, yielding extracts with a high amount of compounds that exhibit antidiabetic activity.