Optimal Ultrasound-assisted Extraction Conditions Research Articles

Isolation and Maximisation of Extraction of Mangiferin from the Root of Salacia chinensis L.

Mangiferin has been reported to exhibit anti-viral, anti-cancer, anti-diabetic, immunomodulatory and hepatoprotective properties. This study aimed to develop an HPLC method to isolate mangiferin from Salacia chinensis L. root; investigate the impact of solvents on yield; optimise the ultrasound-assisted extraction (UAE) technique; and compare mangiferin yield with continuously shaking extraction (CSE) and decoction techniques. The results showed that mangiferin, with a purity of over 88%, could be achieved by HPLC using a mixture of solvent A (water: acetonitrile: orthophosphoric acid, 96.8:3:0.2 (v/v/v)) and solvent B (acetonitrile). Solvent type significantly affected the extraction yield of mangiferin, and a mixture of acetone and water gave the highest extraction yield, as compared to other solvents or mixtures. UAE conditions, such as ultrasonic power, temperature, time and concentration of acetone significantly affected the extraction of mangiferin. Optimal UAE conditions were at an ultrasonic power of 250 W, temperature of 50 °C, acetone concentration of 40% and extraction time of 60 min. These optimal conditions could extract approximately 92 mg, whereas CSE and decoction only extracted 89.20 mg and 58.71 mg of mangiferin, respectively, from 1 g of S. chinensis root. Therefore, these UAE conditions are recommended for the extraction of mangiferin from S. chinensis root for further utilisation.

Tailor-made natural deep eutectic solvents for green extraction of isoflavones from chickpea (Cicer arietinum L.) sprouts

Natural deep eutectic solvents (DESs) have received increasing attention in recent years as emerging green solvents for efficient extraction of bioactive compounds from natural resources. In this study, we aimed to evaluate the potential and effectiveness of DESs with different polarities for extraction of isoflavones from chickpea sprouts. To this end, we examined 20 different DESs based on choline chloride, betaine, and l-proline as hydrogen bond acceptors in combination with different hydrogen bond donors (carboxylic acids, alcohols, sugars, and amine). Extraction efficiency was evaluated based on the extraction yields of four isoflavones (ononin, sissotrin, formononetin, and biochanin A), total flavonoid content, and anti-oxidant activity. On the basis of the results obtained, choline chloride-based DESs containing propylene glycol as a hydrogen bond donor (molar ratio of 1:1) with 30% (v/v) of water was the most effective at extracting isoflavone compounds from chickpea sprouts, compared to conventional solvents. Subsequently, in order to examine the factors contributing to optimal ultrasound-assisted extraction conditions, a Box-Behnken design paired with response surface methodology was implemented. DES water content and extraction temperature were accordingly found to have prominent effects on the extraction yields of isoflavones. Our results indicate that DESs can be used as suitable green solvents for extracting bioactive compounds from various biomaterials.

Optimization of ultrasound-assisted extraction of isogentisin, gentiopicroside and total polyphenols from gentian root using response-surface methodology

In this study we have established optimal conditions for ultrasound-assisted extraction (UAE) of isogentisin, gentiopicroside and total polyphenols from Gentiana lutea root using response surface methodology (RSM) based on central composite design (CCD). The influence of extraction time (X1: 5–65 min), ethanol concentration (X2: 10–90%), solid to solvent ratio (X3: 1:10–1:50) and extraction temperature (X4: 20–80 °C) was analysed. The optimal conditions of extraction procedure were following: X1: 31 min, X2: 49%, X3: 1:42, and X4: 80 °C. Experimentally achieved values were in accordance with those estimated by RSM model, suggesting applicability of the utilized model and the favorable result of RSM application in optimization of extraction parameters.

Optimization of Ultrasound-Assisted Extraction of Phenolic Compounds from Annona muricata By-Products and Pulp

Ultrasound-assisted extraction (UAE) is widely used; however, the efficiency of extraction depends on the raw materials. Therefore, optimization of UAE must be investigated for each type of plant material. By-products from soursop fruit have not been studied as a source of bioactive compounds. In this work, the optimization of UAE conditions (extraction time (5, 10, and 15 min), pulse cycle (0.4, 0.7, and 1 s), and sonication amplitude (40%, 70%, and 100%)) for the extraction of phenolic compounds (soluble, hydrolyzable, condensed tannins, and total polyphenols) from soursop by-products (seed, peel, and columella) and pulp was evaluated using response surface methodology. The optimal conditions for UAE to obtain the highest total polyphenol content from by-products and pulp was dependent on the raw material. Peel resulted in the highest content of total polyphenols (187.32 mg/g dry matter [DM]) followed by columella (164.14 mg/g DM), seed (36.15 mg/g DM), and pulp (33.24 mg/g DM). The yield of polyphenolic content from peel and columella obtained with UAE was higher (32–37%) than conventional extraction for 2 h under stirring (14–16%). The contents of gallic acid (0.36–15.86 µg/g DM), coumaric acid (0.07–1.37 µg/g DM), and chlorogenic acid (9.18–32.67 µg/g DM) in the different parts of the fruit were higher in the extracts obtained by UAE compared with a conventional extraction method (0.08–0.61, 0.05–0.08, 3.15–13.08 µg/g DM, respectively), although it was dependent on the raw materials. Soursop by-products can be functionally important if they are used to extract bioactive compounds by UAE; a technology with high potential for commercial extraction on a large scale.

Optimization of ultrasonic-assisted extraction of flavonoids and anti-oxidant capacity from the whole plant of Andrographis echioides (L.) nees by response surface methodology and chemical composition analysis

Background: Andrographis echioides (L.) Nees is an annual herb mainly distributed in India and Sri Lanka. In traditional medicine system, the plant is used for treating various ailments such as fevers, skin diseases, stomach ache, toothache, snake bite, and eczema. The whole plant of A. echioides was reported as the rich source of flavonoids. Ultrasound-assisted extraction (UAE) is an effective extraction method used for secondary metabolite extraction from various plant materials over conventional methods. Today, the response surface methodology (RSM) is a successful statistical tool used to optimize the various extraction conditions of the secondary metabolite from various sources. Objective: The objective of this study is to optimize the UAE conditions such as ethanol concentration (50%–100%), solvent-to-solid ratio (10–50 mL/g), and sonication time (20–60 min) for the extraction of flavonoids and anti-oxidant capacity (AOC) from A. echioides (L.) Nees whole plant (AEWP) using the RSM strategy with Box–Behnken design (BBD). Materials and Methods: UAE conditions, i.e. ethanol concentration, solvent-to-solid ratio, and sonication time, were optimized with the corresponding responses of flavonoid yield and %DPPHAOCand %ABTSAOCby RSM. The effect of ultrasound on plant material was analyzed using Scanning electron microscope (SEM). The efficiency of the optimized extract was analyzed using Fourier-transformed infrared spectroscopy (FTIR) and liquid chromatography-mass spectra (LC-MS). Results: The BBD provided adequate mathematical models that accurately describe the behavior of the technique and help to predict the flavonoid yield, %DPPHAOCand %ABTSAOCfrom AEWP. The optimized UAE conditions were 77% of ethanol concentration, 35 mL/g of solvent-to-solid ratio, and 41 min of sonication time. Under these extraction conditions, UAE would obtain a maximum of 10.91 ± 0.04 mg CE/g for flavonoid yield, 87.36 ± 0.06% for %DPPHAOC, and 85.14 ± 0.03% for %ABTSAOC.The obtained experimental results of all the responses are in good agreement with the predicted values. SEM analysis explores the effect of UAE compared with the conventional extraction. The FTIR and LC-MS analysis revealed that the optimized extract of AEWP is rich in flavonoids; apart from the known flavonoids, five new flavonoids were identified from this optimization study. Conclusion: The study confirmed that UAE was the effective extraction method for the extraction of flavonoids from AEWP with ethanol as a solvent of choice with a low solvent usage in a reasonable time.

HPLC-PDA method validated for the determination of hibalactone in Hydrocotyle umbellata subterraneous parts and its ultrasound-assisted extraction optimization

In this work, we developed and validated a HPLC-PDA method for the quantification of hibalactone in Hydrocotyle umbellata L., Araliaceae, subterraneous parts extracts and optimized its ultrasound-assisted extraction. Chromatographic separations were carried out with an isocratic mobile phase of acetonitrile/methanol/water (10:65:25), a flow of 0.8mlmin−1, detection at 290nm and C18 column (250×4.6mm, 5μm). The method validation parameters were determined according to Brazilian legislation. The optimization of the hibalactone ultrasound-assisted extraction was performed using Box–Behnken design and response surface methodology. The HPLC method for hibalactone quantification proved to be selective, linear, precise, accurate and robust, being useful for the analysis of hibalactone in H. umbellata subterraneous parts extracts. The optimal ultrasound-assisted extraction conditions were obtained with solid-to-liquid ratio of 1:5gml−1, ethanolic strength of 70% (v/v) and temperature of 65°C. The results can provide support of the quality control and standardization of raw materials from H. umbellata.

Optimization of ultrasound and microwave assisted oil extraction from sea buckthorn seeds by response surface methodology

AbstractSea buckthorn (SB) seeds were used as raw material to obtain SB oil using two extraction methods: ultrasound and microwave assisted extraction. The favorable experimental conditions that maximize the extraction efficiency were investigated by applying response surface methodology (RSM). The selected key independent variables were ultrasonic intensity (UI), temperature, and time for ultrasound assisted extraction (UAE) and microwave power, time, and solid/liquid ratio for microwave assisted extraction (MAE). The results obtained for extraction efficiency under optimal conditions are comparable for the two extraction methods (89.2 ± 0.50% for MAE and 87.4 ± 0.44% for UAE). The operation conditions for maximum extraction efficiency were: 13.77 W/cm2 UI, 40 °C temperature, and 10 min extraction time for UAE and 225 W microwave power, 15 ml/ g solid/liquid ratio, and 20 min extraction time for MAE. The extraction kinetics was characterized using a second order model for optimal conditions for UAE and MAE of SB seed oil.Practical applicationsThis article describes two modern methods of sea buckthorn seed oil extraction: ultrasound assisted extraction (UAE) and microwave assisted extraction. Both methods offer many advantages if they are likened with conventional oil extraction. The results illustrated that both methods give comparable values for extraction efficiency, but with an advantage for UAE. The extraction time for UAE is shorter in comparison with MAE (10 min in comparison with 20 min).

Application of Box-Behnken design for ultrasound-assisted extraction and recycling preparative HPLC for isolation of anthraquinones from Cassia singueana.

Cassia singueana Del. (Fabaceae) is a rare medicinal plant used in the traditional medicine preparations to treat various ailments. The root of C. singueana is a rich source of anthraquinones that possess anticancer, antibacterial and antifungal properties. The objective of this study was to develop an ultrasound-assisted extraction (UAE) method for achieving a high extraction yield of anthraquinones using the response surface methodology (RSM), Box-Behnken design (BBD), and a recycling preparative high-performance liquid chromatography (HPLC) protocol for isolation of anthraquinones from C. singueana. Optimisation of UAE was performed using the Box-Behnken experimental design. Recycling preparative HPLC was employed to isolate anthraquinones from the root extract of C. singueana. The BBD was well-described by a quadratic polynomial model (R2 =0.9751). The predicted optimal UAE conditions for a high extraction yield were obtained at: extraction time 25.00min, temperature 50°C and solvent-sample ratio of 10mL/g. Under the predicted conditions, the experimental value (1.65±0.07%) closely agreed to the predicted yield (1.64%). The obtained crude extract of C. singueana root was subsequently purified to afford eight anthraquinones. The extraction protocol described here is suitable for large-scale extraction of anthraquinones from plant extracts.

Optimization of Ultrasound-Assisted Extraction Followed by Macroporous Resin Purification for Maximal Recovery of Functional Components and Removal of Toxic Components from Ginkgo biloba Leaves.

In the present study, the process of ultrasound-assisted extraction (UAE) followed by macroporous resin purification was successfully developed to achieve maximal recovery of functional components (flavonoids and ginkgolides) with minimal contents of toxic components (alkylphenols) from Ginkgo biloba leaves. Three effective extracted factors including HAc%, EtOH%, and UAE power were screened by Plackett–Burman design (PBD). The important variables were further optimized by rotatable central composite design (RCCD). By combination of PBD and RCCD, the resulting optimal UAE conditions were as follows: HAc% of 1.8%, EtOH% of 63%, ultrasound power of 303 W, G. biloba leaves powder amount of 1.0 g (solvent-to-solid ratio 40 mL/g), particle size of 60 mesh, extraction time of 40 min, and extraction temperature of 45°C. Under the optimum conditions, the yield of flavonoids was 25.1 ± 0.81 mg/g, ginkgolides was 10.6 ± 0.57 mg/g, and alkylphenols was 3.96 ± 0.31 mg/g. Moreover, the further enriching the functional components and removing toxic components from the obtained extracts of G. biloba leaves using the above optimum UAE condition was successfully achieved by macroporous resin DA-201. After column adsorption and desorption on DA-201, the content of total flavonoids was 36.51 ± 1.53%, ginkgolides was 13.24 ± 0.85%, and alkylphenols was 7.0 ± 1.0 μg/g from the obtained dry extracts (drug to extract ratio of 45-50:1) of G. biloba leaves which were complied with Chinese pharmacopoeias.

Valorization of spent shiitake substrate for recovery of antitumor fungal sterols by ultrasound-assisted extraction

The ongoing expansion of mushroom industries has generated enormous spent mushroom substrate with the potential for production of valuable chemicals. This study aimed to investigate ultrasound-assisted extraction (UAE) of fungal sterols from spent shiitake (Lentinula edodes) substrate (SSS) by response surface methodology. The results showed that three variables, including ultrasonic power, extraction time, and liquid–solid ratio, had considerable influence on the extraction efficiency of total fungal sterols with liquid–solid ratio being highly significant for the process. The optimal UAE conditions included liquid–solid ratio 22 mL/g, ultrasonic power 432 W, and extraction time 16 min for the maximum recovery of fungal sterols (151.62 mg ergosterol equivalents/100 g dry weight) from SSS. Further GC-MS analysis indicated that the extracts yielded under the optimal conditions contained ergosterol, ergosta-7,22-dienol, and β-sitosterol, in which ergosterol was the most abundant mycosterol. The extracts also showed a comparable antitumor effect against three cancer cell lines. Practical applications Spent mushroom substrate, a major by-product of mushroom industries, remains a big challenge for the profitability of mushroom industries. Our results indicated that spent shiitake substrate can be valorized by UAE for production of fungal sterols.

Optimizing the extraction parameters of epigallocatechin gallate using conventional hot water and ultrasound assisted methods from green tea

Epigallocatechin gallate (EGCG) is the main polyphenol present in green tea and is also known to possess various beneficial health effects. Extractions of EGCG, epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC) from green tea were investigated by both conventional hot water extraction and ultrasound assisted extraction (UAE) with water and ethanol. Response Surface Methodology was used in order to optimize the extraction conditions for obtaining maximum amount of EGCG in the extracts. Pilot scale conventional hot water extraction and UAE with water in continuous flow mode were also conducted for industrial use. UAE with ethanol was significantly (p<0.05) efficient to extract more EGCG, EGC, ECG, and EC than conventional hot water extraction and UAE with water. At optimum conditions, almost 100 and 50% more EGCG content was obtained in UAE with ethanol than conventional hot water extraction and UAE with water, respectively. The optimal conditions for UAE of EGCG with ethanol were 66.53°C, 43.75min and, 67.81% ethanol. Conventional hot water extraction can easily be scaled up to a pilot scale and can be used for green tea beverage production. UAE should also be scaled up to a pilot scale by an efficient design either using an ultrasound probe in a larger volume continuously or ultrasound probes on each side of the extractor tank with an agitation system.

A novel strategy for isolation and determination of sugars and sugar alcohols from conifers

The ultrasound-assisted extraction method for isolation of 17 sugars and sugar alcohols from conifers with a subsequent hydrophilic interaction liquid chromatography-tandem mass spectrometry method for their determination is proposed. The optimization of extraction parameters was carried out using Taguchi – L9 (34) orthogonal array experimental design for the following parameters—a methanol concentration in the extraction solution, an extraction time, a type of plant sample and an extraction temperature. The optimal ultrasound-assisted extraction conditions were—MeOH concentration – 30% (water – 70%), extraction time – 30 min, type of plant sample – II (grinded leaves 2–4 mm long), extraction temperature – 60 °C. Pure water and acetonitrile were used as eluents in gradient elution mode to separate the analytes. Direct determination of multiple sugars and sugar alcohols was carried out using a mass spectrometric detector operated in a multiple reaction monitoring mode, providing detection limits in the range between 0.1 and 20 ng/mL and good analytical characteristics of the method without derivatization. The developed approach was validated by multiple successive extraction method applied to test its performance on a series of 10 samples, i.e. 2 samples per each of 5 genera: Abies, Larix, Picea, Pinus (Pinaceae) and Juniperus (Cupressaceae), widely distributed in the boreal conifer forests of Eurasia. The novel strategy can be used for profiling of sugars and sugar alcohols in a wide range of plant species.

Use of emerging technologies in the extraction of lupeol, α-amyrin and β-amyrin from sea grape (Coccoloba uvifera L.).

Emerging technologies are being explored to improve extraction yields of phytochemicals or high-value biological compounds. The aim of this study was to evaluate the extraction of lupeol, α-, and β-amyrin from fruit, leaf and stem of the sea grape tree (Coccoloba uvifera L.) using technologies such as Ultrasound Assisted Extraction (UAE) and High Hydrostatic Pressure Extraction (HHPE). Results were compared to conventional extraction (maceration). Analysis with thin-layer chromatography revealed the presence of lupeol in all studied parts of the tree. Optimal extraction conditions for UAE and HHPE were found; the highest concentration of triterpenes was obtained by UAE after evaluating conventional and non-conventional techniques. Finally, analysis of different tree parts and other vegetable sources showed that the best source of triterpenes was the leaf.

Enhanced yield of oleuropein from olive leaves using ultrasound-assisted extraction.

The aim of this study was to optimize the extraction of oleuropein from olive leaves through a systematic study of the effects of different parameters of ultrasound‐assisted extraction (USAE) on the oleuropein yield, in comparison with conventional maceration extraction. A range of operational parameters were investigated for both conventional maceration extraction and USAE: solvent type, olive leaf mass‐to‐solvent volume ratio, and extraction time and temperature. Oleuropein yield was determined using high‐performance liquid chromatography, with total phenolics content also determined. The optimized conditions (water–ethanol, 30:70 [v/v]; leaf‐to‐solvent ratio, 1:5 [w/v]; 2 hr; 25°C) provided ~30% greater oleuropein extraction yield compared to conventional maceration extraction. The total phenolics content obtained using the optimized USAE conditions was greater than reported in other studies. USAE is shown to be an efficient alternative to conventional maceration extraction techniques, as not only can it offer increased oleuropein extraction yield, but it also shows a number of particular advantages, such as the possibility of lower volumes of solvent and lower extraction times, with the extraction carried out at lower temperatures.

Optimization of ultrasound-assisted extraction of okra (Abelmoschus esculentus (L.) Moench) polysaccharides based on response surface methodology and antioxidant activity

This study determined the optimal conditions for ultrasound-assisted extraction of a water-soluble polysaccharide, Raw Okra Polysaccharide, from the fruit of okra using response surface methodology. The optimal extraction temperature, extraction time and ultrasonic power were 59°C, 30min and 522W, respectively, giving a yield of 10.35±0.11%. ROP was further isolated, lyophilized and purified using a DEAE-Sepharose Fast Flow column and Sepharose CL-6B column, revealing three elution peaks subsequently designated ROP −1, −2, and −3, respectively. Of these, ROP-2 showed the highest yield, and was therefore selected for physicochemical analysis and evaluation of antioxidant activity. Gas chromatography, fourier transform infrared spectroscopy, and high-performance liquid chromatography were used to characterize the primary structural features and molecular weight, revealing that ROP-2 is composed of glucose, mannose, galactose, arabinose, xylose, fructose, and rhamnose (molar percentages: 28.8, 12.5, 13.1, 15.9, 9.2, 13.7, and 6.8%, respectively) and has an average molecular weight of 1.92×105Da. A superoxide radical scavenging assay and DPPH radical scavenging assay further revealed the significant in vitro antioxidant activity of ROP-2. These findings present an effective technique for extraction of the natural antioxidant ROP-2, warranting further analysis of its potential application in the food industry.

Optimization of ultrasound-assisted extraction (UAE) of phenolic compounds from olive cake.

The use of ultrasound in ultrasound-assisted extraction (UAE) is one of the main applications of this technology in food industry. This study aimed to optimize UAE conditions for olive cake extract (OCE) through response surface methodology (RSM). The optimal UAE conditions were obtained with extraction temperature of 56°C, extraction time of 3min, duty cycle of 0.6s, and solid to solvent ratio of 3.6%. At the optimum conditions, the total phenolic compounds (TPC) content and antioxidant activity (AA) were measured 4.04mg/g and 68.9%, respectively. The linear term of temperature had the most effect on TPC content and AA of OCE prepared by UAE. Protocatechuic acid and cinnamic acid were characterized as the highest (19.5%) and lowest (1.6%) phenolic compound measured in OCE extracted by UAE. This research revealed that UAE is an effective method to extract phenolic compounds from olive cake. RSM successfully optimized UAE conditions for OCE.

Intensification of bioactive compounds extraction from Feijoa (Feijoa sellowiana Berg.) leaves using ultrasonic waves

In this study, ultrasound-assisted extraction (UAE) of bioactive compounds from Feijoa sellowiana leaves was optimized using response surface methodology. Box-Behnken design was applied to evaluate the effects of ultrasonic intensity, duty cycle and extraction temperature on crude extraction yield (CEY) and radical scavenging activity (RSA) in terms of inhibition of DPPH, OH and ABTS+ radicals. The correlation analysis of mathematical-regression models indicated that quadratic polynomial models could be employed to optimize UAE process. Under the optimal conditions (1569.10W/cm2, 89.00% and 46.00°C) the predicted values of the CEY and RSA of DPPH, OH and ABTS+ were 53.22mgg−1, 78.43%, 62.00% and 81.54%, respectively. High-performance liquid chromatography (HPLC) analysis showed that gallic acid, catechin, ferulic acid, quercetin and apigenin are the major phenolic compounds existed in the extracts. The improvement of UAE was investigated by combining pre-leaching stage (PLS) with optimized UAE conditions (PLS-UAE). Spectrophotometric methods and HPLC analysis results revealed that the bioactive phenolic compounds increased using PLS-UAE, where gallic acid had the highest concentration (123.15±0.34mgg−1). The comparative study results, which has been done between optimized UAE, PLS-UAE and conventional Soxhlet extraction (CSE) revealed that higher CEY (81.11±0.11mgg−1) could be achieved using CSE even through, the quality of extracts in terms of phenolic compounds and RSA was significantly (p-value<0.05) higher using optimized UAE and PLS-UAE. Scanning electron microscopy (SEM) images showed that PLS-UAE can significantly damage the structure of vegetal tissues leads to improved extraction of bioactive compounds.

Ultrasound-assisted extraction of bioactive compounds from Malva sylvestris leaves and its comparison with agitated bed extraction technique.

The effects of ultrasound-assisted extraction (UAE) variables-namely extraction temperature (40-60°C), ultrasonic power (50-150W), and sonication time (40-60min)-on the extractive value (EV) of bioactive phenolics from Malva sylvestris leaves were investigated and optimized using Response surface methodology. The effects of extraction solvents (ethanol, ethyl acetate, and n-hexane) on EV, free radical scavenging activity (FRSA), total phenolic content (TPC), and major bioactive phenolics were studied using agitated bed extraction (ABE), and the results were compared with the UAE findings. Under the optimal UAE conditions (48°C, 110.00W, and 48.77min) the experimental EV was 279.89±0.21mg/g with 71.12±0.15% DPPHsc, 73.35±0.11% ABTSsc, and a TPC of 152.25±0.14mg GAE/g. Ethanolic ABE results in higher EV (320.16±0.25mgg-1) compared to UAE, while the FRSA and TPC values were reduced. HPLC analysis revealed that the concentration of bioactive phenolics increased significantly (p<0.05) under the optimal UAE conditions.

Optimization of ultrasound-assisted extraction of polyphenolic compounds from pomegranate peel using response surface methodology

The pomegranate peel is discarded as waste although it contains high amount of biologically active phenolics and has high value for recycling. In this study we have determined optimal conditions for ultrasound-assisted extraction (UAE) of polyphenols from pomegranate peel using response surface methodology (RSM). The influence of extraction time (X1: 10–60 min), ethanol concentration (X2: 10–90%), solid to solvent ratio (X3: 1:10–1:50) and extraction temperature (X4: 20–80 °C) on total polyphenols content (TPC) as well on content of individual polyphenolic compounds (ellagic acid, gallic acid, punicalagin and punicalin) was investigated. The optimal extraction process conditions were as follows: extraction time of 25 min, ethanol concentration of 59%, solid to solvent ratio of 1:44, and extraction temperature of 80 °C. Experimentally obtained values were in agreement with those predicted by RSM model, indicating suitability of the employed model and the success of RSM in optimizing the extraction conditions.

Optimization of trans lutein from pumpkin (Cucurbita moschata) peel by ultrasound-assisted extraction

In order to avoid the occurrence of high proportion of carotenoid cis isomers during conventional solvent extraction (CSE), ultrasound-assisted extraction (UAE) was used to extract trans lutein and total trans carotenoids from the pumpkin (Cucurbita moschata Duch. cv. Miben) peel. Results showed ethanol–petroleum ether mixture (2:1, v/v) was the suitable solvent for ultrasound-assisted recovery of trans lutein, and high frequency resulted in oxidative degradation of trans lutein from pumpkin peel. The yields of trans lutein and total trans carotenoids positively correlated with ultrasonic power and solvent to material ratio, but negatively correlated with extraction time. Total cis carotenoids gradually increased with the increase of extraction time, but maintained at a low level within a short extraction time. Optimal UAE conditions obtained by Face-centred Central Composite design and response surface methodology were as follows: ultrasonic power of 203W, extraction time of 30min, and solvent to material ratio of 31mL/g. The maximum yields of trans lutein and total trans carotenoids were 237.6μg/g and 344.9μg/g, respectively. However, the total cis carotenoids only accounted for 5.3%. Compared to the CSE, UAE avoided degradation and isomerization, resulting in high yield of trans lutein and trans carotenoids.