Analysis of Chemical Constituents in Wuzi-Yanzong-Wan by UPLC-ESI-LTQ-Orbitrap-MS

Wuzi-Yanzong-Wan (WZYZW), a classical traditional Chinese medicine (TCM) prescription containing Fructus Lych, Semen Cuscutae (fried), Fructus Rubi, Fructus Schisandrae chinensis (steamed) and Semen Plantaginis (fried with salt), is widely used to treat impotence, sterility, spermatorrhea, premature ejaculation, lumbago and post-micturation dribble. However, the chemical profile of WZYZW has not been established yet. In this work, a rapid and sensitive method for systematically screening and identifying the chemical constituents of WZYZW in both positive and negative ion modes using Ultra-Performance LC coupled with ESI-linear ion trap-Orbitrap tandem mass spectrometry (UPLC-ESI-LTQ-Orbitrap-MS) has been developed. Based on the chromatographic and spectrometric data, and referring to the literature, we could tentatively identify 106 compounds, including organic acids, flavonoids, phenylpropanoids, alkaloids and terpenoids. Fourteen ingredients from Fructus Lych were identified, while 10 ingredients were from Semen Cuscutae (fried), 33 ingredients were from Fructus Rubi, 37 ingredients were from Fructus Schisandrae chinensis (steamed), and 20 ingredients were from Semen Plantaginis (fried with salt). The results may provide essential data for further quality control, pharmacological research and clinical evaluation of WZYZW. Furthermore, this study indicates the developed approach based on UPLC-ESI-LTQ-Orbitrap-MS is suitable for characterizing the chemical profiles of TCM prescriptions. This is the first report to provide a comprehensive analysis of the chemical constituents of WZYZW.


Introduction
Chinese herbal prescriptions, the basic form of clinical application of TCM for thousands of years, have been proven by clinical practice to play a positive role in human health. The multi-chemical constituents of Chinese herbal prescriptions are the key to achieving their prevention and treatment effects, so comprehensive analysis of their chemical constituents is the premise and foundation to promote development and innovation in TCM [1][2][3]. Therefore, it is necessary to develop rapid and sensitive methods for identifying the chemical constituents of TCM prescriptions, to facilitate their quality control, safe and effective use in clinic.
Wuzi-Yanzong-Wan (WZYZW), the most classical Chinese herb prescription for nourishing the kidney and strengthening the essence, is called "ancient and modern seed first choice prescription", being firstly detailed recorded in She-sheng-zhong-miao-fang treatise of the Ming Dynasty and widely used to treat syndrome of kidney deficiency and damage of essence, including impotence, sterility,

Optimization of Analytical Conditions
To obtain better chromatographic separation and mass spectrometric detection, four mobile phase systems: methanol-aqueous solution, acetonitrile-aqueous solution, acetonitrile-formic acid aqueous solution and acetonitrile containing formic acid-formic acid aqueous solution were examined, the acetonitrile containing formic acid-formic acid aqueous solution showed a better degree of separation. Formic acid (0.1%) was added to the mobile phase to enhance the intensity of mass signals and improve the peak shape. In addition, the flow rate (0.25, 0.3, 0.35 mL/min), column temperature (25, 30, 40˝C) and injection volume (2, 3, 5 uL) were respectively optimized in this work. The chromatographic separation was better when the chromatographic conditions were as follows: acetonitrile containing formic acid-aqueous formic acid solution, flow rate of 0.3 mL/min, column temperature of 30˝C and injection volume of 3 µL.

Chemical Constituents Identification in WZYZW
Chemical profiles of WZYZW in both negative and positive modes were well separated and detected by using the established UPLC-ESI-LTQ-Orbitrap-MS method. The TIC chromatograms in both ESI modes are shown in Figure 1.
When no standard compounds were available, the structures were elucidated by adopting the following measures to improve the quality of the identifications: firstly, based on the high-accuracy precursor ions obtained from the LTQ-Orbitrap-MS, using Xcalibur 2.1, the element compositions were calculated following some rules (C = 40, H = 100, O = 30, N = 5, Na = 2 and RDB equivalent value = 15). The maximum tolerance of mass error for all the precursor and product ions was set at 5 ppm, which can satisfy the requirements for positive identification. Besides, the most rational molecular formula was sought in different chemical databases such as the Spectral Database for Organic Compounds SDBS (http://sdbs.db.aist.go.jp) and Massbank (http://www.massbank.jp). When several matching compounds with the same formula were found, the structures were sought in the chemical information of the compounds from the five crude drugs of WZYZW. The component herb from which each compound was derived was confirmed by individually analyzing the herbs with the same UPLC-LTQ-Orbitrap-MS method. Finally, the chemical structures were further confirmed by combining the chromatographic data, the high resolution and accurate mass product ion information provided by data-dependent scan from MS n experiments and referring to literature references. Moreover, the fragmentation patterns and pathways of the standards contributed to further confirming the derivatives of the reference compounds, then, the structure could be tentatively identified. A total of 106 compounds of WZYYW were thus identified or tentatively identified, including 35 flavonoids, 34 phenylpropanoids, 17 organic acids, 8 alkaloids, 11 terpenoids and one miscellaneous ingredient; 14 ingredients from Fructus Lych were identified, 10 ingredients from Semen Cuscutae (fried), 33 ingredients from Fructus Rubi, 37 ingredients from Fructus Schisandrae chinensis (steamed), and 20 ingredients from Semen Plantaginis (fried with salt). Table 1

summarizes their information.
Molecules 2015, 20, page-page calculated following some rules (C = 40, H = 100, O = 30, N = 5, Na = 2 and RDB equivalent value = 15). The maximum tolerance of mass error for all the precursor and product ions was set at 5 ppm, which can satisfy the requirements for positive identification. Besides, the most rational molecular formula was sought in different chemical databases such as the Spectral Database for Organic Compounds SDBS (http://sdbs.db.aist.go.jp) and Massbank (http://www.massbank.jp). When several matching compounds with the same formula were found, the structures were sought in the chemical information of the compounds from the five crude drugs of WZYZW. The component herb from which each compound was derived was confirmed by individually analyzing the herbs with the same UPLC-LTQ-Orbitrap-MS method. Finally, the chemical structures were further confirmed by combining the chromatographic data, the high resolution and accurate mass product ion information provided by data-dependent scan from MS n experiments and referring to literature references. Moreover, the fragmentation patterns and pathways of the standards contributed to further confirming the derivatives of the reference compounds, then, the structure could be tentatively identified. A total of 106 compounds of WZYYW were thus identified or tentatively identified, including 35 flavonoids, 34 phenylpropanoids, 17 organic acids, 8 alkaloids, 11 terpenoids and one miscellaneous ingredient; 14 ingredients from Fructus Lych were identified, 10 ingredients from Semen Cuscutae (fried), 33 ingredients from Fructus Rubi, 37 ingredients from Fructus Schisandrae chinensis (steamed), and 20 ingredients from Semen Plantaginis (fried with salt). Table 1 summarizes their information.

Flavonoids
Flavonoids have a diphenylpropane skeleton bearing two benzene rings (A and B) connected by a pyran ring attached to the A ring, and are further divided into several subclasses (flavones, flavonols, flavanones, flavanonols, anthocyanidins, aurone, halcones and isoflavonoids). In this work, four types of flavonoids were found in WZYZW by UPLC-ESI-LTQ-Orbitrap-MS. Taking compound 53 as an example, the precise molecular weight is 623. 16248  was identified as isorhamnetin-3-O-β-D-rutinoside. Its mass spectrum and proposed fragmentation pathways in negative mode are shown in Figure 2.     12 ). Moreover, they had the similar fragment ions of m/z 301, 255 and 151 in the MS n spectra, but different max UV absorption wavelengths (λ max ), as the λ max of compound 34 were 254 and 356 nm, and compound 37 showed λ max peaks at 254 and 346 nm. Considering the different retention times, compounds 34 and 37 were tentatively identified as hyperoside and isoquercitrin, respectively (see Table 1).
Similarly, based on the chromatographic behavior and MS n spectrometry for further confirming the fragmentation patterns as shown above, a total of 35 flavonoids were tentatively identified, including 15 flavones and derivatives, 16 flavonols and derivatives, three flavanone glycosides, and one flavanonol, which are summarized in Figure 3.
Compounds 34 and 37 were considered to be isomers as they displayed the same [M − H] − ions at m/z 463.08887 (C21H19O12) and 463.08740 (C21H19O12). Moreover, they had the similar fragment ions of m/z 301, 255 and 151 in the MS n spectra, but different max UV absorption wavelengths (λmax), as the λmax of compound 34 were 254 and 356 nm, and compound 37 showed λmax peaks at 254 and 346 nm. Considering the different retention times, compounds 34 and 37 were tentatively identified as hyperoside and isoquercitrin, respectively (see Table 1).
Similarly, based on the chromatographic behavior and MS n spectrometry for further confirming the fragmentation patterns as shown above, a total of 35 flavonoids were tentatively identified, including 15 flavones and derivatives, 16 flavonols and derivatives, three flavanone glycosides, and one flavanonol, which are summarized in Figure 3.

Phenylpropanoids
Phenylpropanoids have one or more C6-C3 structures and there are three main subclasses: simple phenylpropanoids, coumarins and lignans. In the present study, 34 phenylpropanoids were found in WZYZW, including two simple phenylpropanoids, four coumarins and 28 lignans. The classification of these compounds is shown in Figure 4. Consequently, compound 102 was tentatively identified as deoxyschizandrin. The MS n mass spectra and the fragmentation pathways of deoxyschizandrin are shown in Figure 5. As with the fragmentations

Phenylpropanoids
Phenylpropanoids have one or more C 6 -C 3 structures and there are three main subclasses: simple phenylpropanoids, coumarins and lignans. In the present study, 34 phenylpropanoids were found in WZYZW, including two simple phenylpropanoids, four coumarins and 28 lignans. The classification of these compounds is shown in Figure 4.
Compounds 34 and 37 were considered to be isomers as they displayed the same [M − H] − ions at m/z 463.08887 (C21H19O12) and 463.08740 (C21H19O12). Moreover, they had the similar fragment ions of m/z 301, 255 and 151 in the MS n spectra, but different max UV absorption wavelengths (λmax), as the λmax of compound 34 were 254 and 356 nm, and compound 37 showed λmax peaks at 254 and 346 nm. Considering the different retention times, compounds 34 and 37 were tentatively identified as hyperoside and isoquercitrin, respectively (see Table 1).
Similarly, based on the chromatographic behavior and MS n spectrometry for further confirming the fragmentation patterns as shown above, a total of 35 flavonoids were tentatively identified, including 15 flavones and derivatives, 16 flavonols and derivatives, three flavanone glycosides, and one flavanonol, which are summarized in Figure 3.

Phenylpropanoids
Phenylpropanoids have one or more C6-C3 structures and there are three main subclasses: simple phenylpropanoids, coumarins and lignans. In the present study, 34 phenylpropanoids were found in WZYZW, including two simple phenylpropanoids, four coumarins and 28 lignans. The classification of these compounds is shown in Figure 4.   The MS n mass spectra and the fragmentation pathways of deoxyschizandrin are shown in Figure 5. As with the fragmentations described above, the other phenylpropanoid compounds were also tentatively identified. However, six groups of isomers (compounds 40 and 42, 72 and 73, 74 and 77, 90 and 97, 94,  96, 99 and 101, 104 and 106) had the same molecular weights in the MS spectra, similar fragment ions in the MS n spectra and similar max UV absorption wavelengths. Thus we could not distinguish them, and these structures will require further confirmation (see Table 1). described above, the other phenylpropanoid compounds were also tentatively identified. However, six groups of isomers (compounds 40 and 42, 72 and 73, 74 and 77, 90 and 97, 94, 96, 99 and 101, 104  and 106) had the same molecular weights in the MS spectra, similar fragment ions in the MS n spectra and similar max UV absorption wavelengths. Thus we could not distinguish them, and these structures will require further confirmation (see Table 1).

Organic Acids
The UPLC-ESI-LTQ-Orbitrap method was applied to comprehensively characterize the organic acids in this study, and the results showed that three types of organic acids could be detected in WZYZW: four aliphatic organic acids, three alicyclic organic acids and 10 phenolic acids. The specific details are displayed in Figure 6.

Organic Acids
The UPLC-ESI-LTQ-Orbitrap method was applied to comprehensively characterize the organic acids in this study, and the results showed that three types of organic acids could be detected in WZYZW: four aliphatic organic acids, three alicyclic organic acids and 10 phenolic acids. The specific details are displayed in Figure 6. Compound 15 produced a [M − H] − ion at m/z 167.03420 (C8H7O4), and its fragment ions showed the losses of CH3, CO2 and CH3 + CO2, respectively. Thus, compound 15 was identified as vanillic acid, which was confirmed by MS n experiments. Similarly, the above fragmentation patterns were applied to further confirm the identities of the other organic acids compound, and finally, 17 compounds were identified as organic acids.

Terpenoids
As displayed in Figure  Using high-resolution MS n mass spectrometry and the similar method of analysis of the aforementioned fragmentations, a total of 11 terpenoids were found: one iridoid (compound 16) was identified as geniposidic acid; 10 triterpenes- compounds 69, 76, 80, 81, 83, 84, 92, 95, 98 and 100 were identified as nigranoic acid, kadsuric acid, rosolic acid, 2α,3α,19α-trihydroxyolean-12-ene-28-oic acid, ganwuweizic acid, arjunolic acid, corosolic acid, maslinic acid, oleanolic acid and ursolic acid. Compounds 80, 81 and 84, 98 and 100, and 92 and 95, constituted three groups of isomers with similar fragmentation pathways in their MS spectra, so we could not precisely identify them by Mass (see Table 1).  Table 1). Similarly, eight alkaloids were identified in WZYZW and confirmed using MS n data: abromine (1), nicotinic acid (5), thiamine (6), taurine (14), atropine (19), sophoranol (82), n-methylcytisine (85), and matrine (93). To summarize, in this study, a reliable and rapid UPLC-ESI-LTQ-Orbitrap-MS method has been established for the first comprehensive analysis of the phytochemical constituents of the Chinese herbal prescription WZYZW. This method revealed that UPLC-ESI-LTQ-Orbitrap-MS was useful for screening and identifying the complex constituents of WZYZW. Based on the method, a total of 106 compounds were tentatively characterized. In contrast to the published papers, it is noteworthy that this work detected more components. Our results provide essential data for further pharmacological studies and clinical evaluation of WZYZW and be useful for quality control of WZYZW, so as to guarantee its safe use in the clinic. Compound 15 produced a [M´H]´ion at m/z 167.03420 (C 8 H 7 O 4 ), and its fragment ions showed the losses of CH 3 , CO 2 and CH 3 + CO 2 , respectively. Thus, compound 15 was identified as vanillic acid, which was confirmed by MS n experiments. Similarly, the above fragmentation patterns were applied to further confirm the identities of the other organic acids compound, and finally, 17 compounds were identified as organic acids.

Miscellaneous
Riboflavin (compound 10) was also identified in WZYZW by its [ To summarize, in this study, a reliable and rapid UPLC-ESI-LTQ-Orbitrap-MS method has been established for the first comprehensive analysis of the phytochemical constituents of the Chinese herbal prescription WZYZW. This method revealed that UPLC-ESI-LTQ-Orbitrap-MS was useful for screening and identifying the complex constituents of WZYZW. Based on the method, a total of 106 compounds were tentatively characterized. In contrast to the published papers, it is noteworthy that this work detected more components. Our results provide essential data for further pharmacological studies and clinical evaluation of WZYZW and be useful for quality control of WZYZW, so as to guarantee its safe use in the clinic.

Preparation of WZYZW Samples
A standard preparation of WZYZW was made in accordance with the 2015 version of the Chinese Pharmacopoeia. Fructus Lych, Semen Cuscutae (fried), Fructus Rubi, Fructus Schisandrae chinensis (steamed), and Semen Plantaginis (fried with salt) (8:8:4:2:1) were weighed, then crushed to powder (40 mesh size) and immersed in 10-fold volume of water for 1 h and heated. After boiling, heating was ontinued until the volume was reduced by 5-fold. The mixture was filtered through gauze while hot, concentrated to 1 g crude drug/mL, and freeze-dried to a powder. Finally refined honey (85 g) was mixed with freeze-dried powder (100 g) to make boluses of WZZYW for the experiments. Freeze-dried single herb extract powders were prepared as described for WZYZW. Freeze-dried samples of WZYZW (250 mg) were extracted with 50 mL of methanol with the aid of ultrasound for 60 min. The extracts were centrifuged at 10,000 rpm for 15 min at 4˝C, the supernatant was collected and filtered through a filter (0.22 µm), and the filtrate was collected for UPLC-LTQ-Orbitrap analysis. Respective standard stock solutions of 19 components were prepared at concentrations of 50 ng/mL by weighing the desired amount of each component into a volumetric flask and dissolving it in 100% ethanol; the 19 samples were filtered through a filter (0.22 µm), and the filtrates were analyzed by UPLC-LTQ-Orbitrap.

Liquid Chromatography Conditions
The chromatographic separation was performed on an ACQUITY UPLC TM BEH C 18 column (1.7 µm, 2.1 mmˆ100 mm) using an ACQUITY UPLC TM system (Waters Corporation, Milford, MA, USA) equipped with quaternary pump, vacuum degasser, autosampler and photodiode array detector. A linear gradient elution of A (HCOOH:H 2 O = 0.1:100) and B (HCOOH:CH 3 CN = 0.1:100) was used. The optimized gradient program is shown in Table 2. The flow rate was 0.3 mL/min and column temperature was set at 30˝C, the injection volume was 3 µL. The effluent was roughly split at a ratio of 3:1 (v/v) before entering the ESI source.

ESI-MS/MS Detection
The LTQ/Orbitrap mass spectrometer (Thermo Scientific, Bremen, Germany) was equipped with an ESI source operating in positive and negative ESI mode. The negative ion mode operation parameters were as follows: capillary voltage, 35 V; electrospray voltage, 3.0 kV; capillary temperature, 350˝C; sheath gas, 30 (arbitrary units); auxiliary gas, 10 (arbitrary units); tube lens, 110 V. The positive ion mode operation parameters: capillary voltage, 25 V; electrospray voltage, 4.0 kV; capillary temperature, 350˝C; sheath gas, 30 (arbitrary units); auxiliary gas, 5(arbitrary units ); tube lens, 110 V. Samples were detected by full-scan mass analysis from m/z 100 to 1000 at a resolving power of 30,000 with data-dependent MS 2 analysis triggered by the three most-abundant ions from the predicted precursor list followed by MS 3 analysis of the most-abundant product ions. To avoid performing many repeated data acquisitions on the same sample, dynamic exclusion is used for the data collection with an exclusion duration of 60s and the repeat count was set at 5 with a dynamic repeat time at 30 s. Collision-induced dissociation (CID) was performed with an isolation width of 2 Da. The collision energy was set to 35%. An external calibration for mass accuracy was carried out before the analysis. The measured masses were within 5ppm of the theoretical masses. The data analysis was achieved using XCalibur softwarev2.0.7 (Thermo Fisher Scientific).

Data Processing
The data analysis was processed using Thermo Xcaliber 2.1 workstation (Thermo Fisher Scientific) for peak detection and peak alignment, the raw data were processed by the computer-based NMDF approach.

Conclusions
In this study, a rapid, sensitive and reliable UPLC-ESI-LTQ-Orbitrap-MS method was established for screening and identifying the chemical constituents of WZYZW in both the positive and negative ion modes. Based on the chromatographic and spectrometric data, and referring to the literature, we were able to tentatively characterize 109 compounds, including organic acids, flavonoids, phenylpropanoids, alkaloids and terpenoids. In all 14 ingredients from Fructus Lych were identified, 11 ingredients from Semen Cuscutae (fried), 35 ingredients from Fructus Rubi, 37 ingredients from Fructus Schisandrae chinensis (steamed), and 21 ingredients from Semen Plantaginis (fried with salt). Our results broadens the chemical knowledge of WZYZW, which should be helpful for the quality control of WZYZW, and for further research on the pharmacokinetic studies and the health and medical properties of WZYZW. Moreover, with the successful application of the UPLC-ESI-LTQ-Orbitrap-MS to characterizing the constituents of WZYZW, it is suggest that this method offer a rapid, sensitive and high throughput methodology for the identification of constituents of TCM prescriptions and herbal medicines.