Qualitative and Quantitative Analysis of Dan-Deng-Tong-Nao Capsules by HPLC-DAD-MS/MS

Dan-Deng-Tong-Nao capsules (DDTNCs), a traditional Chinese medicinal preparation consisting of Radix Salvia miltiorrhiza, Radix Pueraria lobata, Erigeron breviscapus, Rhizoma chuanxiong has been used for the treatment of apoplexy and the syndrome of apoplexy involving both collaterals and meridians caused by obstruction of collaterals by blood stasis in China. In this paper, a HPLC-DAD-MS/MS method was successfully developed for qualitative and quantitative analysis of major components in DDTNCs for the first time. Twenty-six compounds were identified by comparison of their retention times and MS spectra with those elucidated standards or recorded literatures, and six of them (danshensu, 5-hydroxymethylfurfural, 3,4-dihydroxybenzaldehyde, epicatechin, puerarin and salvianolic acid A) were simultaneously determined by HPLC-DAD quantitatively. The analytical method was fully validated and successfully applied for quantitative and fingerprint analysis of DDTNCs from fifteen different production batches, results indicated that the proposed approach was applicable for the routine analysis and quality control of DDTNCs. *Corresponding author: Jianzhong Shen-Tu, Research Center for Clinical Pharmacy, State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University, 79# Qingchun Road, Hangzhou 310003, PR China, Tel: 86-571-87236537; E-mail: youtai.1234@163.com Received February 19, 2016; Accepted February 29, 2016; Published June 08, 2016 Citation: Zheng Y, Hu X, Lin M, Zhai Y, Wu L, et al. (2016) Qualitative and Quantitative Analysis of Dan-Deng-Tong-Nao Capsules by HPLC-DAD-MS/MS. Mass Spectrom Purif Tech 2: 110. doi:10.4172/2469-9861.1000110 Copyright: © 2016 Zheng Y. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Introduction
"Dan-Deng-Tong-Nao capsules" (DDTNCs) is a commonly used traditional Chinese formula medicine, which is prepared (extracted, purified and combined) from four commonly used Chinese herb drugs, including Radix Salvia miltiorrhiza, Radix Pueraria lobata, Erigeron breviscapus and Rhizoma chuanxiong. DDTNCs have the ability of activating blood circulation to dissipate blood stasis, removing obstruction in the meridians and heart-nourishing effects [1,2]. It was usually used for the treatment of apoplexy and the syndrome of apoplexy involving both collaterals and meridians caused by obstruction of collaterals by blood stasis [3,4].
Chemical constituents of the four component herbs of DDTNCs have been intensively studied [5][6][7][8]. However, little is known about the chemical composition of DDTNCs, and the current analysis methods could not reflect the quality of it [9,10]. Therefore, practicable and reliable quality evaluation method to monitor the systematic chemical profile changes of DDTNCs in the procedure from preparation and storage to clinic usage is of significant importance.
In this paper, an HPLC-DAD-MS/MS method was established for rapidly identifying and reliably determining multiple components in DDTNCs, and was then successfully applied to quantitative and fingerprint analysis of fifteen batches of DDTNCs samples. This study represents the first detailed investigation of the components of DDTNCs and provides an applicable method for its comprehensive quality evaluation.

Experiment Apparatus, materials, chemicals and reagents
HPLC-DAD analysis was carried out on an Agilent 1200 Series HPLC with diode-array detector; MS/MS was performed on an Agilent 6410 Triple Quad MS with an electrospray ionization (ESI) interface (Agilent Technologies, Inc., USA). Fifteen batches of DDTNCs were purchased from different pharmacies in China. Standards of danshensu, 5-hydroxymethylfurfural, 3,4-dihydroxybenzaldehyde, epicatechin, puerarin and salvianolic acid A (Structures shown in Figure 1) were purchased from the National Institute for the Control of Pharmaceutical and Biological Products(Beijing, China), their purities (>98%) were determined by normalization of the peak area detected by HPLC-UV. HPLC grade reagents (methanol, acetonitrile and formic acid) were obtained from Merck (Darmstadt, Germany). Water was purified using a Milli-Q system (Milford, MA, USA).
The ESI-MS/MS detection was acquired directly after DAD measurement in positive ionization mode, and recorded on a mass range of m/z 100-1000. Drying gas (Nitrogen) temperature was set at 350°C with a flow rate of 10.00 L/min and nebulizer pressure of 45.00 psi. Capillary voltage was 4000 V.
3,4-dihydroxybenzaldehyde, 580 μg/mL for puerarin, 125 μg/mL for epicatechin and 300 μg/mL for salvianolic acid A) was prepared in 50% methanol and stored away from light at 4°C until used. Working solutions of the lower concentration were prepared by appropriate dilution of the stock solution with 50% methanol. The chromatogram of the six standards is shown in Figure 2.

Sample solution preparation
The powder of DDTNCs (about 50 mg) was extracted with 20.0 mL solvent composed of 80% methanol in water (v/v) for 20 min in an ultrasonic bath. 1.0 mL of the extract solution was centrifugation at 15,000 rpm for 5 min and 5 μL of the supernatant was injected into the HPLC-DAD-MS/MS system. Content for each component was calculated from its corresponding calibration curve.

Identification of components from DDTNCs
The traditional methods to isolate different standard compounds from herb drugs are restricted and laborious. However, HPLC coupled with MS is a powerful approach to solve this problem. MS, a selective and sensitive detector, allows the detection of minor or even trace amounts of constituents from complex matrix. Furthermore, MS provides abundant structural information and thus, facilitates the structural identification of unknown compounds. In this study, HPLC-DAD-MS/MS was adopted to identify the chemical constituents of DDTNCs.
ESI in both negative and positive mode was tried to detect components in DDTNCs. The results indicated that more peaks could be detected in positive mode than in negative mode. For identification of components contained in the crude extracts of DDTNCs, mass fragmentation with MS 2 spectrometry data provided valuable information. An efficient transmission of molecular ions and fragment ions was obtained by ramping the collision energy from 10 V to 50 V for the rapid identification of trace level components in the crude extracts with large sample throughput.
In the positive ESI-MS spectra of DDTNCs, the quasi-molecular ion peaks of components always appeared as [M+H] + ion, except for peak 17. Most peaks of components had the fragments of [M+H-18] + , and MS/MS spectra with standard compounds. Finally, 26 compounds were characterized by comparing their retention times, UV spectra and MS data with those of reference compounds or literature data [11][12][13][14][15][16], and most of them belonged to flavonoids, the representative cleavage pathway of flavonoid is shown in Figure 3. The results of the MS/MS and UV data are listed in Table 1, and the chemical structures of the identified compounds are shown in Figure 1.
[M+H-28] + and [M+H-15] + corresponding to the loss of "H 2 O", "CO" and "CH 3 ", respectively. Furthermore, there were some fragments of [M+H-176] + which corresponded to the loss of "Glu" and indicated the structure belonged to glycosides.
Through on-line DAD and ESI-MS spectra, six major peaks: 1, 2, 4, 7, 9 and 26 in the chromatogram of DDTNCs ( Figure 2) were identified by comparing their retention time, ultraviolet absorption

Validation of the method
Calibration curve, limits of detection and quantification: Solutions containing the six standards at six different concentrations were analyzed. The calibration curve of each analyte was constructed by plotting the peak area versus the corresponding concentration. The mixed standards solution was further diluted to a certain concentration to explore the limits of detection (LOD) and quantification (LOQ). The LOD and LOQ were determined at a signal-to-noise (S/N) ratio of 3 and 10, respectively. The satisfactory results regarding regression equations, correlation coefficients, linear ranges, LODs and LOQs were listed in Table 2. The high correlation coefficient values (R 2 >0.9992) indicated good linearity between their peak areas (y) and investigated compound concentration (x, μg/ml) in relatively wide concentration ranges.
Precision, stability and accuracy of the method: The intra-and inter-day precisions were determined by continuously injecting the sample solution for six replicates on the same day and by measuring it once a day for three consecutive days, respectively. Stability was assessed by analyzing the same sample solution at different time within 24 h (0, 8, 12, 24 h) at room temperature.
Recoveries test that reflecting method's accuracy was performed employing the method of standard addition. Three different quantities (low, medium and high) of the authentic standards were added into the known real sample. The recovery was figured out according to the following formula: Recovery (%)=(amount detected−original amount)/ amount spiked × 100%, and RSD (%)=(SD/mean) × 100%. All the results were estimated on the ground of relative standard deviation (RSD%). Tables 3 and 4 list the results of precision, stability and recovery test, which suggested that the RSDs for the six compounds are less than 5.0%, the average recoveries of the six compounds is 94.6-104.8%. These data indicated that the established HPLC-DAD method was precise, accurate and sensitive enough for simultaneously quantitative determination of these six compounds in DDTNCs.

Fingerprint analysis of DDTNCs:
The chromatograms of different samples have to be standardized, so as to perform fingerprint analysis. The process of standardization included the selection of ''common peaks'' in chromatograms and the normalization of retention times of all the common peaks [17]. In this study, the extracts of fifteen samples of DDTNCs were analyzed. More than thirty peaks appeared in the HPLC-DAD chromatographic fingerprints as shown in Figure 2. The peak of puerarin (peak 9) was selected as a reference peak because it is an intense peak situated nearly in the middle of chromatogram. Among all the peaks observed, fifteen of them (1-5, 7, 9, 10, 14, 16, 17, 21, 22, 26 and 27) were defined as common peaks.
Similarity analysis was performed by using the software "Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicines'' (Version 2004A), which used to generate the mean chromatogram, and calculate the similarities of the sample chromatograms with mean chromatogram with cosine method. The average chromatogram of the fifteen batches of commercial samples was taken as the standard characteristic fingerprint of DDTNCs. It was subsequently compared with the chromatograms from fifteen batches of DDTNCs to generate the similarity values which were in the range of 0.671~0.991 ( COA: caffeoyl-2,7-anhydro-2-octulopyranosonic acid; b. CQA: caffeoylquinic acid   y, peak area; x, concentration of compound (μg/ml); limit of detection (LOD), S/N=3; limit of quantification (LOQ), S/N=10 Table 2: Linear regression data, LOD and LOQ of the six investigated components from DDTNC.   of DDTNCs samples varied considerably, indicating the quality of DDTNCs was inconsistent.

Quantitative analysis of DDTNCs:
The proposed HPLC method was applied to analyze six components in fifteen batches of DDTNC. The quantitative analyses were performed by means of the external standard method. Samples were prepared as described in section "2.3". The typical chromatogram is given in Figure 2. The results, shown in Table 5, indicate that puerarin showed the highest amount (43.60-72.70 μg/mg), followed by 5-hydroxymethylfurfural (1.24-7.96 μg/mg), danshensu (1.48-5.04 μg/mg) and salvianolic acid A (0.85-4.33 μg/mg). Our results showed that the contents of the six analytes in different batches are noticeably different, which may occurred due to various factors such as cultivation, harvest, storage and so on.

Optimization of HPLC conditions
The selection of the HPLC conditions was guided by the requirement for obtaining chromatograms with better resolution of adjacent peaks. The optimization of HPLC conditions was performed using standard mixture and sample extract. Different HPLC parameters including mobile phase (acetonitrile-water, methanolwater, acetonitrile-acid aqueous solution, methanol-acid aqueous solution), category of column (Agilent Zorbax SB-C 18 250 mm × 4.6 mm i.d., 5 μm, Agilent Zorbax Extended-C 18 250 mm × 4.6 mm i.d., 5 μm, Agilent Zorbax SB-Aq column 250 mm × 4.6 mm i.d., 5 μm) and column temperature (25, 35, 45°C) were examined and compared. The results showed that the best resolution and retention behavior were achieved when the methanol-water/ acetic acid (100/0.2, v/v) system and the column (Agilent Zorbax SB-Aq column 250 mm × 4.6 mm i.d., 5 μm) were used. Finally, an optimized HPLC condition was developed by comprehensively evaluating the resolution, baseline, elution time. Meanwhile, linear gradient was applied in HPLC procedure to obtain a perfect resolution, which could be examined by DAD and ESI-MS spectrometer. DAD detection was employed at wavelength range of 190-400 nm to investigate the UV spectra of the compounds in DDTNCs. It was found that UV at 280 nm was the best wavelength for the detection, because the most peaks can be detected under 280 nm. The optimal HPLC condition was shown in section "2.2", and the representative HPLC-DAD chromatograms of DDTNCs samples are shown in Figure 2.

Optimization of extraction conditions
In order to obtain as many peaks as possible, related extraction conditions were examined and evaluated. Firstly, different extraction solvents (water and aqueous methanol of 20%, 50%, 70%, 80%, 90% and methanol (v/v)) were compared, the total number of peaks and the content of the six quantitative indicators were used as response to evaluate the extraction solvents. The results showed that the peak intensities of middle eluted constituents increased with the increase of methanol concentration in the extraction solution, while the peak intensities of early eluted constituents decreased with the increase of methanol concentration. The sample extracted with 80% methanol exhibited higher contents of the indicators than those with other tested solvents, which was further confirmed by the HPLC-DAD quantitative analysis method (Figure 4). Therefore, 80% methanol was selected as Batch no. The similarity of DDTNCs was calculated professional software named Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine (Version 2004A). Table 5: Contents of the six investigated components and similarity of DDTNCs from fifteen different batches. the extraction solvent for both identification and quantitative analysis of DDTNCs. Then extraction repetitions (1, 2, 3 times) and extraction time (10 min, 20 min, and 30 min) were also evaluated. Finally, by comparing the areas of characteristic peaks in chromatograms obtained under different conditions, the optimal condition for extraction of DDTNCs was selected and presented in detail in section "2.3".

Conclusion
In the last decades, only one or two markers or pharmacologically active components in TCMs were usually employed for evaluating the quality of them, which could not give a complete picture of TCMs, because multiple constituents are usually responsible for its therapeutic effects. The proposed HPLC-DAD-MS/MS method makes it possible to comprehensively evaluate the quality of the commonly used TCM (DDTNCs) through a simultaneous qualitative and quantitative analysis of multi-components. This method has been applied successfully to simultaneously identify and quantify the main components in different batches of DDTNCs. Results indicated: (1) the established method is rapid, simple and accuracy; (2) most ingredients of DDTNCs belong to flavonoids and phenolic acids; (3) the quality of the collected samples was inconsistent, which could be easily affected by the exterior factors, not only the processing methods, but also the harvested time and habitats of the four raw herbs.