J. Cent. South Univ. Technol. (2008) 15: 59-63
DOI: 10.1007/s11771-008-0013-z
Microwave assisted-semi bionic extraction of lignan compounds from
Fructus Forsythiae by orthogonal design
TU Qiu-yun(涂秋云)1,2, ZHOU Chun-shan(周春山)2, TANG Jian-ping(汤建萍)3
(1. Neurology Department of the Third Xiangya Hospital, Central South University, Changsha 410013, China;
2. School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China;
3. College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, China)
Abstract: Microwave assisted-semi bionic extraction (MASBE) process for lignans from Fructus Forsythiae was studied. The influences of solvent pH value, microwave power, dosage of solvent and irradiation time were investigated. Optimum extracting parameters were determined by orthogonal experiments as follows: pH value of solvent at first extraction is 5.5-6.0, that at the second extraction is 7-8; microwave power is 700 W; mass ratio of Fructus Forsythiae to water is 1?12; irradiation time is 10 min, and extracting times is two. Under these optimal conditions, the yield of lignans reaches 0.364%. Compared with the conventional extraction methods, the MASBE process has the advantages of high extraction rate, high extraction selectivity.
Key words: lignans; Fructus Forsythiae; microwave assisted-semi bionic extraction; orthogonal test
1 Introduction
Fructus Forsythiae is dried fruit of Forsythia Suspenasa (Thunb.), and produced chiefly in Shandong province, Hebei province and Shanxi province, China. It was recorded in ancient pharmacopoeia that Fructus Forsythiae has the function of clearing heat and detoxifying, eliminating stagnation to relieve swellings. It is indicated for diseases such as symptoms due to warm-heat, hieropyra, macula, carbuncle and oncotic ulcer, as well as dysuric stranguria[1-3]. Lignans in Fructus Forsythiae include phillygenin, phillyrin, (+)-epinoresinol, (+)-pinoresinol, mataresinol and arctigenin[4-6]. It was proved by the pharmacological experimental studies that these components have the effects of antibiotic action, cardiotonic action, regulating blood pressure, protecting liver, dredging blood vessel and can inhibit the activity of cyclic AMP phosphodiesterase[7-10].
Because most of lignans are chiral molecular and the biologic activity of the synthesis product is low, method of separation and preparation of lignans from Fructus Forsythiae is important. But as reported, conventional methods to extract lignans, such as reflux extraction, ultrasonic extraction, have deficiencies in certain aspects such as long extraction time, low efficiency or uneasy treatment[11-13]. So it needs to find a new method. Based on the principles of microwave- assisted extraction and semi-bionic extraction, microwave assisted-semi bionic extraction(MASBE) method was used for the extraction of lignans from Fructus Forsythiae to get higher extraction yield and better bio-utilization. The purpose of this work is to develop a new MASBE method and investigate the influence of condition parameters on the extraction of lignans from Fructus Forsythiae.
2 Experimental
2.1 Reagents and materials
Fructus Forsythiae was purchased from Hunan Herbal Medicine Co. (Changsha, China), and ground to fine power to 14 μm. Phillygenin standard samples were purchased from Sigma Corporation. All the used chemicals were analytically pure, and distilled water was used in the experiment．
2.2 Main equipment
756MC model spectrophotometer, Midi 700 microwave extractor and pHS-25 model pH meter were used.
2.3 Extraction process
Water was acted as extraction solvent and pH value was regulated by solution of H2SO4 or NaOH. Each sample was dipped for 5 min in extraction solvent, then extracted in microwave extractor. When MASBE was completed, the extraction solution was filtered immediately. Finally all extraction solutions of each sample were mixed and concentrated under reduced pressure to get the extract of Fructus Forsythiae.
2.4 Product analysis
Content of total lignan in the extract was determined by spectrophotometric method, using phillygenin as standard sample. According to the reported method in Ref.[14], the relationship between concentration of phillygenin (c) and absorbance(A), the regression equation, A= 0.009 52c-0.002 63, was established.
2.5 Single factor experiment
Some lignans are easily decompounded under strong acid condition. And according to the theory of semi-bionic extraction, pH value in the first extraction has important effect on the extraction yield. So lignans in Fructus Forsythiae were extracted by MASBT procedure under the same conditions except solvent pH at the first extraction. Then single factor experiments of microwave power and irradiation time were performed.
2.6 Orthogonal experiment
The L16 (54) program of orthogonal experiment was designed for the MASBE procedure of lignans from Fructus Forsythiae, so the effects of pH, microwave power, dosage of solvent and irradiation time on the extraction yield were investigated.
3 Results and discussion
3.1 Effect of pH value of solvent at first extraction
Fig.1 shows the effect of pH value of solvent at the first extraction on extraction yield of lignans. It can be seen that extraction yield of lignans is greatly influenced by pH value of solvent in first extraction. When pH value of solvent at first extraction is in the range of 4.5-6.0, the extraction yield of lignans keeps at higher value. So levels of pH value of solvent at the first extraction in orthogonal experiment are selected to be 4.5, 5.0, 5.5 and 6.0.
Fig.1 Effect of pH value of solvent on extraction yield of lignans at the first extraction
3.2 Relationship between extraction yield of lignans and microwave power
Table 1 lists the effect of microwave power on extraction yield of lignans. The results show that the yield of lignans is greatly influenced by microwave power. When microwave power changes from 300 to 750 W, the extraction yield of lignans keeps at higher value. So levels of microwave power in orthogonal experiment, 231, 385, 539 and 700 W, are selected.
Table 1 Relationship between extraction yield of lignans and power of microwave
3.3 Relationship between extraction yield of lignans and irradiation time
The relationship between extraction yield of lignans and irradiation time is listed in Table 2. Table 2 shows that the extraction yield of lignans is related to irradiation time. When the irradiation time varies in the range of 4.5-10 min, the extraction yield of lignans keeps at higher value. So the irradiation time in orthogonal experiment, 4, 6, 8 and 10 min, are selected.
Table 2 Relationship between extraction yield of lignans and irradiation time
3.4 Orthogonal experiment
The levels and factors for orthogonal experiment are listed in Table 3, and the results of orthogonal experiment are listed in Table 4. As listed in Table 4, microwave power is the most important factor to the extraction yield of lignans among the five selected factors. The importance of five factors to extraction yield is in a sequence from high to low as follows: microwave power, pH value of solvent at the second extraction, pH value of solvent at the first extraction, mass ratio of Fructus Forsythiae to water, irradiation time.
Table 5 lists the variance analysis results of orthogonal experiment. The efficiency curves of factors in orthogonal experiments are shown in Fig.2. According to these analysis results, it can be found that microwave power has significant effect on the extraction yield of lignans among five selected factors, and pH of solvent also has greater impact on the extraction yield.
Table 3 Levels and factors of orthogonal experiments
Table 4 Orthogonal experimental program and results of extraction (N=3)
Table 5 Variance analysis of orthogonal experiment results
Fig.2 Effect of factors on efficiency of extraction in orthogonal experiments: (a)pH value of solvent at the first extraction; (b)pH value of solvent at the second extraction; (c) Microwave power; (d) Mass ratio of Fructus Forsythiae to water; (e) Irradiation time
After considering the result of orthogonal experiment and the cost, the optimal conditions of production process were determined as follows: pH value of solvent at the first extraction, 5.5-6.0; pH value of solvent at the second extraction, 7-8; microwave power, 700 W; mass ratio of Fructus Forsythiae to water, 1?12; irradiation time, 10 min, and extracting times, 2. Under these optimal conditions of MASBE the extraction yield of lignans is 0.364% (N=6), relative standard deviation (RSD)=5.4%.
3.5 Comparison of MASBE and conventional extract- ion
The comparison of MASBE and conventional extraction is listed in Table 6. The results show that the time of heat reflux extraction, extraction at room temperature and ultrasound-assisted extraction is respectively about 12-144 times longer than that of extraction with MASBE. MASBE can greatly reduce the extraction time with higher extraction yield of lignans.
In recent years, microwave assisted extraction has been developed for the extraction of active components of herb. Microwave-assisted extraction has higher extraction efficiencies for breaking down cell walls and dissolve some insoluble substances by microwave electromagnetic field[15-16]. Semi-bionic extraction is also a new method combined integer medicament study with molecule medicament study. It simulates body absorbing environmental test: imitating administration by mouth and transporting through gastrointestine, then extracting materials under acid circumstance and extracting them under base circumstance in turn[17-18]. In this work microwave assisted-semi bionic extraction (MASBE) was used. Because MASBE combines virtues of microwave extraction and semi-bionic extraction, it can extract and keep more activity components at a shorter time, avoiding damage of active components under high temperature environment. The results of experiments in our studies confirm that compared with traditional extraction methods, MASBE has higher efficiency and can save time and power for extracting lignans from Fructus Forsythiae. And drug effect of product by MASBE is stronger than those of products by other methods because of simulating body absorbing environment.
Table 6 Comparison of results of extraction with MASBE and other extraction methods
4 Conclusions
1) The microwave assisted semi bionic method can be used to extract lignan compounds from Fructus Forsythiae.
2) The optimal parameters of MASBE are determined as follows: pH of solvent at the first extraction, 5.5-6.0; pH of solvent at the second extraction stage, 7-8; microwave power, 700 W; mass ratio of Fructus Forsythiae to water, 1?12, irradiation time, 10 min and extracting twice.
3) Under these optimal conditions, the extract yield of lignans reaches 0.364%. MASBE is a good method with higher efficiency and less extraction time for extracting lignans from Fructus Forsythiae.
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(Edited by YANG Hua)
Foundation item: Project(06SK3042) supported by the Science and Technology Commission Foundation of Hunan Province, China
Received date: 2007-06-02; Accepted date: 2007-07-18
Corresponding author: TU Qiu-yun, PhD; Tel: +86-13786132760; E-mail: qiuyuntu@126.com
