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Total Phenolic Content, Total Flavonoid Content and Radical Scavenging Activity from Zingiber zerumbet Rhizome using Subcritical Water Extraction
Abstract and Figures
Subcritical water extraction (SWE) is an alternative technique implemented water as a solvent. The objective of this work was to extract Zingiber zerumbet rhizome using SWE at a temperature range from 100ºC to 180ºC with duration from 5 to 25 min. The extracts were analysed for total phenolic content (TPC), total flavonoid content (TFC) and radical scavenging activity (RSA). Soxhlet extraction using ethanol was used for a comparison purpose. Results showed the highest TPC and TFC was obtained at 180ºC and 25 min extraction, with the yield of 18.52 mg GAE/gDW and 2.34 mg QE/gDW of rhizome for TPC and TFC, respectively. RSA at peak of 83.9 % inhibition at the condition of 180ºC and 10 min extraction. In comparison to Soxhlet extraction, the extract after SWE gives the highest amount of TPC and RSA. However, the values for TFC are lower as compared to ethanolic extract. Therefore, SWE process for Zingiber zerumbet extract is favourable for higher TPC and RSA. A direct linear correlation between the RSA with the TPC and TFC of the extracts shows that a strong correlation was observed between TPC and the RSA with the R² obtained was 0.910 as compared to moderate correlation (R²=0.785) perceived in TFC. Thus, it shows higher radical scavenging activity in Zingiber zerumbet was contributed by phenolic content as compared to its flavonoid content. In overall, SWE is a potential alternative extraction process that should be further explored. © 2018 Materials and Energy Research Center. All rights reserved.
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... Mao et al. [29] pointed out that the health benefits of ginger are primarily due to the presence of phenolic compounds. Moreover, numerous authors have conducted experiments with ginger (Zingiber officinale Roscoe) [30][31][32][33][34], as well as other ginger species such as Zingiber zerumbet [26,35,36], Zingiber montanum [37], Zingiber officinale rubrum, and Zingiber officinale amarum [32]. Other raw materials used include avocado (Persea americana) [38], cherimoya leaves (Annona cherimola Mill) [27] and grape seeds (Vitis vinifera) [21]. ...
... However, the results of TPC and AA quantification are dependent on the extraction method and conditions used. Various authors have employed high-pressure and temperature water extraction [21,26,27,[34][35][36]38]. Ultrasound-assisted extraction has also been widely used [30,31,33,37], along with infusion and decoction methods [32] and organic solvent extraction [21,27,31,35]. ...
... However, the results of TPC and AA quantification are dependent on the extraction method and conditions used. Various authors have employed high-pressure and temperature water extraction [21,26,27,[34][35][36]38]. Ultrasound-assisted extraction has also been widely used [30,31,33,37], along with infusion and decoction methods [32] and organic solvent extraction [21,27,31,35]. ...
Global demand for food shows an increasing trend, which implies that volumes of food waste also increase. These wastes contain bioactive compounds that are not properly utilized or valorized. It was reported that ginger waste contains phenolic compounds with high antioxidant activity. Thus, this study aimed to evaluate the effect of temperature, time, and particle size on the total phenolic content (TPC) and antioxidant activity (AA) of ginger (Zingiber officinale R.) waste aqueous extract using the Pressurized Liquid Extraction (PLE) method with water as the sole solvent. Box-Behnken design was used. The sample was 1.60 kg of dried ginger peel powder. Data analysis was performed with Minitab ® 19.1 (64-bit). TPC ranged from 10.42 to 14.1 mg GAE/g, and AA (DPPH method) ranged from 72.9 to 111.9 μmol TE/g. The model explained 81.07% of AA’s total variability. Positive correlation was found between TPC and AA (Pearson's ρ = 0.58, p < 0.05). Response optimization values were 126 °C and 38 min. Temperature was a significant factor (p < 0.05) influencing AA, while time and particle size were not significant. Higher temperatures, longer extraction times and smaller particle sizes increase TPC and AA of the ginger waste aqueous extract.
... Mao et al. [32] highlighted that the health benefits of ginger are primarily attributed to its phenolic compounds. Additionally, numerous researchers have carried out studies on Zingiber officinale Roscoe [33][34][35][36][37] and other ginger species, including Zingiber zerumbet [29,38,39], Zingiber montanum [40], Zingiber officinale rubrum, and Zingiber officinale amarum [35]. The primary contribution of this work, compared to previous studies on ginger, lies in the evaluation of the phenolic content and antioxidant activity of Zingiber officinale peel extract using the PLE method with water as the sole solvent. ...
... However, the quantification of TPC and AA is highly dependent on the extraction method and conditions employed. Several authors have utilized the PLE method [21,29,30,[37][38][39]41], while ultrasound-assisted extraction has also been widely applied [33,34,36,40]. Additionally, infusion and decoction techniques [35], as well as organic solvent extraction [21,30,34,38], have been used in various studies. ...
... Several authors have utilized the PLE method [21,29,30,[37][38][39]41], while ultrasound-assisted extraction has also been widely applied [33,34,36,40]. Additionally, infusion and decoction techniques [35], as well as organic solvent extraction [21,30,34,38], have been used in various studies. Regarding findings from previous studies using the PLE method, Razak et al. [37] reported AA values of 71.46 ± 2.44% inhibition. ...
Global food demand is rising, leading to increased food waste, which contains underutilized bioactive compounds. The Pressurized Liquid Extraction (PLE) method employs high temperature and pressure to maintain the solvent in a liquid state above its boiling point, thereby minimizing extraction time and solvent usage. Ginger waste is known to contain bioactive compounds with significant antioxidant activity. We aimed to assess the effect of temperature, time, and particle size on the total phenolic content (TPC) and antioxidant activity (AA) of ginger (Zingiber officinale R.) waste aqueous extract using the PLE method. A Box–Behnken design with 16 runs was employed. Each extraction utilized 40 g of the sample and was conducted at a constant pressure of 20 bar with a solvent ratio of 27:1 mL/g. Data analysis was performed with Minitab® 19.1 (64-bit). TPC ranged from 10.42 to 14.1 mg GAE/g, and AA ranged from 72.9 to 111.9 μmol TE/g. The model explained 81.07% of AA’s total variability. Positive correlation was found between TPC and AA (Pearson’s ρ = 0.58, p < 0.05). The optimized extraction conditions were a temperature of 126 °C, an extraction time of 38 min, and a particle size between 355 and 500 μm. Temperature significantly influenced AA (p < 0.05), while time and particle size were not significant factors. To enhance future research, conducting nutritional and functional studies on the extracted compounds would provide valuable insights. Lastly, evaluating the economic feasibility of using PLE for ginger waste valorization should be considered to support its commercial application.
... 25 g of dried Z.zerumbet with a mean particle size of 2.36 mm was weighed and extracted with 500 ml ethanol for 8 hours. The best operating condition was based on the previous study [19], [20]. The extraction temperature was kept constant at the boiling point of ethanol (78.10℃) and was monitored using an infrared laser thermometer (AR300, China). ...
... The RSA of the extract was analyzed against the stable DPPH (2,2-diphenyl-1-picrylhydrazyl, Sigma Aldrich, Germany). According to previous literature [19], [23]. Initially, the samples were diluted at a ratio of 10:40 of extract to 80% ethanol. ...
... TPC was evaluated using Folin-Ciocalteu modified method [19], [24]. Initially, the extract was diluted in distilled water with a ratio of 1:10 v/v. ...
Extraction is crucial for herbal extraction to ensure high quality of bioactive compounds from natural herbs. In the current work, Zingiber Zerumbet was extracted via subcritical water extraction (SWE) and is compared with the conventional solvent extraction, Soxhlet. The quality of the extract was investigated in terms of zerumbone concentration, radical scavenging activity (RSA) and total phenolic content (TPC). For zerumbone concentration, extraction via SWE gave 19.82 ±0.004 mg/g as compared with Soxhlet; 28.51±0.079 mg/g. However, the extraction time required for SWE to yield such concentration only required 40 minutes instead of Soxhlet which took 480 minutes. The same trend was recorded for RSA, which yielded 60.70±0.070% inhibition for SWE and 68.81±0.024% inhibition from Soxhlet extraction. In contrast to TPC, SWE recorded a higher response than Soxhlet extraction, which was 19.19±0.003 mgGAE/g DW, while Soxhlet; 8.30±0.019 mgGAE/g DW. Therefore, the SWE method is more favorable for obtaining a higher value of TPC, slightly good in antioxidant properties but lower zerumbone concentration value than organic solvent extraction. However, the reduced extraction time was almost 12 times quicker for SWE when compared with Soxhlet extraction. Overall, SWE is a promising alternative environmentally friendly since it only uses water as solvent and is comparable to the conventional method.
... It is related to their ability to prevent oxidative damage of materials in plants, vegetables, fruits and to their role as natural antioxidants for humans. [1,2]. ...
... As polar solvent, the dielectric constant of water is high because of the hydrogen bond in its structure [12]. Water extraction become an interesting method which is widely applicable in bioactive extraction because it is natural, non-toxic, low cost green solvent and has been recognized as a safe solvent by food and nutraceutical industries [13,2]. This method is an alternative of green technology in collecting functional compounds located inside of materials without a harmful impact on the environment and biomaterial by using water as non-toxic solvents. ...
Proanthocyanidin extraction for antioxidant material from intact red sorghum grains in agitated vessel had been investigated. The optimization and the appropriate kinetic evaluation were useful to conduct the engineering design of the developed process. Concentrations of the proanthocyanidin compounds in the aqueous extract were affected by the agitation speed and extraction time. The objectives of this research were to determine the optimum values of agitation speed and time for getting maximum extraction performance and to develop the appropriate kinetic model for illustrating the extraction phenomena. This research also evaluated the characteristics of the obtained extract. The optimum conditions of extraction were determined using Response Surface Methodology. The concentration of proanthocyanidin compound in the extract was predicted to be maximum at 405.05 rotations per minute (rpm) of agitation speed and 133.03 minutes of extraction time. The values of R ² of the regression equations were 99.45%. In the kinetic modeling, the mechanistic model turns to be much more accurate than the second order kinetic. The extract from the optimum process had 0.837 mg/ml of proanthocyanidin concentration and was proven to be effective in scavenging 64.02% of free radicals in the 100 μM DPPH in 30 minutes.
... SWE which so-called as pressurized hot water extraction is an environmentally-safe method that is generally applied for medicinal plants extraction. Subcritical water refers to water in liquid state at condition between boiling point (T=100°C, 0.1MPa) and critical point (374°C, 22.1MPa) [10,11]. At atmospheric condition, water is a polar solvent with high dielectric constant owing to presence of hydrogen bonds in its structure. ...
... Selain itu, pelarut yang mempunyai polariti yang sama dengan bahan terlarut boleh meningkatkan keberkesanan proses pengekstrakan (Altemimi et al. 2017). Disebabkan kepelbagaian sebatian bioaktif yang berbeza dalam setiap tumbuhan, maka keterlarutan terhadap jenis pelarut juga berbeza bagi setiap tumbuhan (Truong et al. 2019 Penentuan jumlah kandungan fenol dijalankan menggunakan kaedah Folin-Ciocalteu (Mokhtar et al. 2018). Reagen Folin-Ciocalteu disediakan pada nisbah 1:10 menggunakan air suling. ...
Serai Acheh (Elettariopsis smithiae) ialah tumbuhan herba daripada famili Zingiberaceae (Halia) yang digunakan dalam perawatan tradisi. Matlamat kajian ini adalah untuk mengkaji potensi rizom serai Acheh sebagai punca antioksidan semula jadi, mengenal pasti komponen meruap dan menilai perubahan warna yang disebabkan oleh pengekstrakan pada pelbagai parameter. Sampel dikeringkan dalam ketuhar vakum (45 ℃, 0.4 bar) dan diekstrak dengan air suling pada 1:50 (sampel: pelarut) pada pelbagai suhu (50 ℃, 60 ℃, 70 ℃) dan masa (40 min, 80 min, 120 min). Pengekstrakan pada suhu 60 ºC selama 120 minit mencatatkan TPC tertinggi iaitu sebanyak 84.59 mg GAE/g manakala pengekstrakan pada suhu 60 ºC selama 40 minit merekodkan nilai FRAP tertinggi iaitu 1176.4 μM FeII/g berbanding sampel lain. Sampel yang diekstrak pada suhu 70 ºC selama 80 minit mencatatkan peratus penyingkiran radikal DPPH tertinggi iaitu 83.37%, namun begitu tiada perbezaan yang signifikan (p>0.05) berbanding sampel yang diekstrak pada suhu 60 ºC selama 80 minit. Nilai peratus penyingkiran radikal kation ABTS tertinggi iaitu 69.59% juga dicatatkan pada suhu pengekstrakan 60 ºC selama 80 minit. Pengekstrakan rizom serai Acheh pada suhu 60 ºC selama 80 minit adalah yang paling optimum. Kesan perlakuan suhu dan masa pengekstrakan juga menyumbang kepada perubahan warna (ΔE) ekstrak rizom serai Acheh yang signifikan (p<0.05) terhadap sampel kawalan. Sebatian eukaliptol, fensil alkohol, borneol, fensil asetat dan 4-etinil-4,8,8-trimetil-2-metilidenabisiklo [5.2.0] nonana adalah sebatian meruap yang dominan ditemui pada sampel kawalan dan sampel rizom serai Acheh yang telah diekstrak pada keadaan optimum. Kandungan antioksida dan kehadiran sebatian meruap membuktikan bahawa rizom serai Acheh mempunyai potensi sebagai punca antioksida semula jadi dan menjadi alternatif kepada antioksida sintetik.
... The ability of phenolic compounds to capture free radicals in living material systems causes their capability to prevent oxidative damage for extending the food shelf life and reducing the risk of oxidative diseases [2]. The phenolic compounds derived from secondary metabolites are potential to be processed as natural antioxidant or herbal medicine which is recognized more effective, safe and eco-friendly than the synthetic product [2][3][4]. ...
Growth in industrial production, urbanization, overexploitation of resources and inadequate waste
management, has led to the emergence of many environmental issues. Among these, the generation of
wastewaters from various sources causing pollution has been the most afflicting one. With the changing
habits of people, the preference is shifting towards eating outside rather than cooking at homes thus the
number of restaurants continued to increase at a fast rate throughout the world. The rapid growth of
restaurants has a negative impact on environmental sustainability due to the generation of restaurant
wastewater (RWW). RWW with other pollutants also contains the fats and oils scrapes and leftovers, lards,
used cooking oil and seasonings causing the formation of greasy textured substance called FOG (fat, oil, and
grease). FOG causes serious blockages of sewer leading to sewage backups, sewage spills, manhole
overflows, increase in the frequency of cleaning, and breakage leading to replacement of piping system.
Therefore, proper, and efficient treatment is recommended for RWW containing FOG before discharging it
to the sewers or water bodies to avoid the problems associated. Hence, converting FOG into renewable energy
sources of various forms including biomaterials and biodiesel seems to be a promising solution. The study
will provide an insight of the characterization of restaurant wastewater, emphasizing on the generation of
FOG and its deleterious effects on sewers, treatment plants and the people. The study will also provide an
overview of the sustainable management of FOG for energy recovery and its transformation into various
renewable resources of energy.
Response surface methodology is a series of statistical techniques that can be used to design experiment, modeling and evaluating the effect of variables on the final obtained results and optimization of process conditions. In this research, optimization of the solvent extraction method of bioactive compounds from seedless barberry (Berberis vulgaris) was carried out using response surface methodology. Central composite design was employed with 13 treatments and 5 replications in central points and the effect of variable factors of temperature (50-70ºC) and extraction time (40-120 minutes). The amount of anthocyanin content, vitamin C, phenolic contents and antioxidant activities of extracted barberry were measured. Close agreement was found between experimental and predicted values of model. Effects of extraction temperature and time were found to be significant on all responses. According to these results, optimal extraction conditions were identified at 50 °C temperature for120 minutes. In this condition the maximum of phenolic compounds, anthocyanin, antioxidant activities and vitamin C contents were 585.725 mg GAE/100ml, 208.392 mg/l, 84.2603% and 1292.56 ppm respectively. The results showed that this methodology could be applied in the extraction of bioactive compounds in the natural product industry.
Background
Zingiber zerumbet (L.) is a traditional Malaysian folk remedy that contains several interesting bioactive compounds of pharmaceutical quality.
Methods
Total flavonoids and total phenolics content from the leaf, stem, and rhizome of Z. zerumbet at 3 different growth stages (3, 6, and 9 months) were determined using spectrophotometric methods and individual flavonoid and phenolic compounds were identified using ultra-high performance liquid chromatography method. Chalcone Synthase (CHS) activity was measured using a CHS assay. Antioxidant activities were evaluated by ferric reducing antioxidant potential (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. The antibacterial activity was determined against Gram-positive and Gram-negative bacteria using the disc diffusion method.
Results
Highest content of total flavonoid [29.7 mg quercetin equivalents (QE)/g dry material (DM)] and total phenolic (44.8 mg gallic acid equivalents (GAE)/g DM) were detected in the rhizome extracts of 9-month-old plants. As the plant matured from 3 to 9 months, the total flavonoid content (TFC) and total phenolic content (TPC) decreased in the leaf, but increased significantly in the rhizomes. Among the secondary metabolites identified, the most abundant, based on the concentrations, were as follows: flavonoids, catechin > quercetin > rutin > luteolin > myricetin > kaempferol; phenolic acids, gallic acid > ferulic acid > caffeic acid > cinnamic acid. Rhizome extracts from 9-month-old plants demonstrated the highest CHS activity (7.48 nkat/mg protein), followed by the 6-month-old rhizomes (5.79 nkat/mg protein) and 3-month-old leaf (4.76 nkat/mg protein). Nine-month-old rhizomes exhibited the highest DPPH activity (76.42 %), followed by the 6-month-old rhizomes (59.41 %) and 3-month-old leaves (57.82 %), with half maximal inhibitory concentration (IC50) of 55.8, 86.4, and 98.5 μg/mL, respectively, compared to that of α- tocopherol (84.19 %; 44.8 μg/mL) and butylated hydroxytoluene (BHT) (70.25 %; 58.6 μg/mL). The highest FRAP activity was observed in 9-month-old rhizomes, with IC50 of 62.4 μg/mL. Minimal Inhibitory Concentration (MIC) of Z. zerumbet extracts against Gram-positive and Gram-negative bacteria ranged from 30 to >100 µg/mL. Among the bacterial strains examined, Staphylococcus aureus was sensitive to the leaf extract of Z. zerumbet, with MIC of 30.0 μg/mL and other strains were sensitive to the rhizome extracts.
Conclusions
Three- and 9-month-old plants are recommended when harvesting the leaf and rhizome of Z. zerumbet, respectively, in order to obtain effective pharmaceutical quality of the desired compounds.
Curcumin is a natural bioactive compound originated from the rhizomes of turmeric (Curcuma longa L.). This study was performed to investigate formic acid and microwave assisted extraction of curcumin from turmeric (Curcuma longa L.). In order to enhance the curcumin extraction, different parameters such as particle size, effect of pretreatment with water, radiation intensity and type of solvent were investigated. For analysis of curcumin content, two methods were developed. Spectrophotometric methods at the stage of optimization and high performance liquid chromatography (HPLC) for determination of the purity of curcumin were used. At particle size of 0.21mm and input power of 100W using acetone as organic solvent, the highest curcumin extraction yields were achieved. The results showed that water is a suitable modifier for the pretreatment of turmeric with microwave irradiation. For purification of curcumin in HPLC analysis, methanol and water were used as co-solvents. Maximum obtained curcumin purity was 82.4%.
Zingiber zerumbet (L.) Roscoe ex Sm., Zingiberaceae, is a perennial, aromatic and tuberose plant that grows in humid locations. Also known as bitter ginger, Z. zerumbet is traditionally found throughout Asia, where it is widely used in foods, beverages and for ornamental purposes. The viscous juice present in the inflorescence of the plant is rich in surfactants and is also known as “ginger shampoo”. The rhizome can be macerated in ethanol and used as a tonic and a stimulant. In Brazil Z. zerumbet is found in the Amazon region, in Taruma-mirim and Puraquequara (rural areas of Manaus, Amazon, Brazil). The main chemical compounds found in Z. zerumbet are terpenes and polyphenols. Zerumbone, a sesquiterpene, is the principal bioactive compound of Z. zerumbet and it is widely studied for its medicinal properties. The extracts and isolated metabolites of Z. zerumbet have exhibited the following properties: anti-inflammatory, antioxidant, antidiabetic, anticancer, antimicrobial, analgesic and antiviral. The National Institute of Amazon Research in Brazil is currently conducting studies using extracts from this plant to obtain compounds active in tumor models. The aim of this review is to provide a overview about the main aspects related with pharmacognosy and pharmacology of Z. zerumbet published in the literature over the last decade.
Subcritical water extraction (SWE) of essential oil from Matricaria Chamomilla L.(M. Chamomilla L.) was performed and compared with conventional method including hydro distillation. The percentage of main extracted components of different temperatures (100, 125, 150 and 175 o c) and water flow rates (1, 2 and 4 ml/min) were investigated at 20 bar pressure and 0.50 mm mean particle size in SWE. The separation and identification of the components were carried out by gas chromatography (GC)-flame ionization detection and GC-mass spectrometry. The best operating conditions for the SWE of M. Chamomilla L. were determined to be at 150 o c temperature and 4 ml/min flow rate for 120 min extraction time. In comparison with hydro distillation method, the SWE method resulted in a more valuable essential oil with respect to the oxygenated components.
Subcritical water extraction (SWE) avoids the use of organic solvents when extracting active compounds. The SWE of phytochemicals from Phlomis umbrosa Turcz (PT) and the effect of antioxidant activity were investigated while varying the extraction temperature (from 100 °C to 200 °C) and time (from 5 to 25 min). The maximum yields of total polyphenols (142.02 ± 5.67 mg/g PT, mean ± SD) and flavonoids (33.69 ± 3.01 mg/g PT) were obtained for an extraction temperature and time of 200 °C and 20 min, respectively. The correlation of antioxidant activities in terms of their total phenolics and flavonoids contents suggest that the ABTS⁺ assay better reflects the antioxidant contents in SWE from PT than does the DPPH assay for extraction temperatures from 110 °C to 200 °C. At higher temperatures around 200 °C, SWE extracts affect the antioxidant activity due to the presence of not only flavonoids but also nonflavonoid phenolic compounds including prenylated flavonoids.
Industrial relevance
This study used subcritical water extraction (SWE) for the practical applications of the SWE process that extracts antioxidant compounds from medicinal herb such as Phlomis umbrosa Turcz. SWE is excellent technology to selectively extract bioactive compounds using temperature-dependent dielectric constant properties of water. As the temperature of water is increased, the polarity of water decreases. That's why it is selective extraction. The use of SWE in the present study was associated with high efficiency and antioxidant activities. These results indicate that SWE is an efficient and rapid method for extracting phytochemicals, and a safer product only using purified water. SWE has a potential to develop a commercial process for the extraction of phytochemicals. This method can be easily implemented on an industrial scale.
Water can be considered, in many cases, the greenest solvent. In the last years, the number of publications which used water as a green extraction solvent has notably increased. One of the main reasons that makes water an interesting solvent are the physicochemical changes of water from ambient to near-critical conditions under which subcritical water extraction (SWE) (or pressurized hot water extraction (PHWE)) can be performed. This review presents a critical overview about the greenness of water as extraction solvent. The changes of its physicochemical properties from ambient to near-critical conditions will be briefly described, and some of the most relevant applications of SWE published from 2015 to 2017 will be discussed. Finally, some basic ideas about different methodologies that can be employed to evaluate the greenness of an extraction process will be provided.
Subcritical water extraction was investigated as a green technology for the extraction of phenolic compounds from Crocus sativus petals. A Box-Behnken design was utilized to determine the optimal extraction conditions. Extraction temperature (120–160 °C), extraction time (20–60 min) and water to solid (W/S) ratio (20–40 mL/g) were considered as the variables for the extraction of phenolic compounds. A second order polynomial model was fitted to each response and the regression coefficients were determined using least square methodology. There was a good correspondence between the experimental data and their predicted counterparts. The optimum conditions of extraction were estimated to be W/S ratio of 36 mL/g, temperature of 159 °C and time of 54 min. Extraction using these optimized conditions achieved the best TPC (1616 mg/100 g), TFC (239 mg/100 g), %DPPHsc (86.05%) and FRAP value (5.1 mM). Principal components analysis (PCA) allowed a better understanding of interactions between properties of extracted phenolic antioxidants.
An efficient extraction of bioactive compounds from licorice was developed using subcritical water. This study aimed at investigating the impacts of parameters on the composition and antioxidant property of the extract. It was found that total phenolics (TP), total flavonoids (TF), glycyrrhizic acid (GL), and antioxidant activity (TAA) were significantly affected by the time, pH, and temperature. The parameters of 20 min and pH 8 were preferred. The maximum values were obtained at 200°C (TF, TP), and 140°C (GL). At 280°C, TAA reached the highest level. Subcritical water extraction was confirmed to be an environmentally-friendly and efficient method.