Journal of Analytical Methods in Chemistry
Volume 2021 (2021), Article ID 5546446, 13 pages
https://doi.org/10.1155/2021/5546446

Research Article

Quality Evaluation of Artemisia capillaris Thunb. Based on Qualitative Analysis of the HPLC Fingerprint and UFLC-Q-TOF-MS/MS Combined with Quantitative Analysis of Multicomponents

Ying Dai,¹ Zhihua Dou,1,2,3 Rongrong Zhou,² Lin Luo,³ Li Bian,² Yufeng Chen,² Jinhua Tao,³ and Zhixian Chen⁴

¹School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, Jiangsu, China
²Nantong Third People’s Hospital, Nantong University, Nantong 226006, Jiangsu, China
³School of Pharmacy, Nantong University, Nantong 226019, Jiangsu, China
⁴Department of Pharmacy, Nantong Health College of Jiangsu Province, Nantong 226010, Jiangsu, China

Correspondence should be addressed to Rongrong Zhou; zhourongrong824@163.com and Zhixian Chen; zxchen81@163.com

Received 25 January 2021; Accepted 17 March 2021; Published 21 April 2021

Academic Editor: Eliseo Herrero Hernandez

Copyright © 2021 Ying Dai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

In this study, a new method was developed for the comprehensive quality evaluation (QE) of Artemisia capillaris Thunb. (A. capillaris, named Yinchenhao in Chinese), which is one of the most commonly used herbal medicines (HMs). First, fingerprints of 31 batch samples of A. capillaris were determined by HPLC, the reference fingerprint was established, and the common peaks were assigned. Second, the components of common peaks in the HPLC fingerprints were identified by ultrafast liquid chromatography- (UFLC-) Q-TOF-MS/MS. Finally, the contents of the components unambiguously confirmed by reference substances were determined, and the correlation between the contents of chlorogenic acid and the contents of others was analyzed. The results showed that there were 20 common peaks in the HPLC fingerprints of 31 batch samples. The components of these 20 common peaks were identified as ten organic acids, eight flavonoids, and two others. Among nine organic acids such as 1-caffeoylquinic acid, neochlorogenic acid, chlorogenic acid, caffeic acid, cryptochlorogenic acid, 1,3-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid, three flavonoids such as rutin, hyperoside, and isoquercetin, and one other p-hydroxyacetophenone, a total of 13 ones were unambiguously identified by comparison with reference substances; one caffeoylquinic acid glucoside and one flavone di-C-glucoside were detected in A. capillaris for the first time. There were some differences in the contents of 13 components in different samples; chlorogenic acid could be regarded as the quality marker of A. capillaris. The current established method in this study can be used for the comprehensive QE of A. capillaris and can also provide reference for the QE of the other HMs.

1. Introduction

The quality and quality evaluation (QE) method is crucial in the effectiveness and safety assessment of herbal medicines (HMs) [1]. The method for the QE of TCMs must be based on the holistic principle, and fingerprint describes integral characterization and reflects interactive aspects of complex components; therefore, it can offer the possibility of evaluating quality of HMs following the overall principle [2]. HPLC fingerprint has become the most widely used method due to its high reproducibility and sensitivity [3]. The HPLC fingerprint method applied to QE of HMs is mainly based on the similarity of fingerprints and the presence or absence of chromatographic peaks among samples [4, 5]; however, this method cannot identify what these peaks are. Q-TOF-MS/MS is a kind of tandem mass spectrometry providing a high mass resolution and accurate mass measurement for the structural elucidation of unknown chemicals [6] and can be used in the identification of common peaks in HPLC fingerprints. Based on the qualitative analysis of fingerprint, the quantitative analysis of multiple components is the key step of QE of HMs [5].

Artemisia capillaris Thunb. (A. capillaris, named Yinchenhao in Chinese) is one of the most commonly used HMs [7], which has been used in China, Korea, and Japan for a long time to treat liver and choleretic disorders, such as cholestasis, jaundice, liver fibrosis, and hepatitis [7–9]. The major components contained in A. capillaris include organic acids, flavonoids, coumarins, essential oil, and others, such as p-hydroxyacetophenone [7]. A characteristic fingerprint was developed to determine the volatile constituents in essential oil of A. capillaris by GC-MS [10], but the systematic study on the HPLC fingerprint of A. capillaris and the identification of common peaks by Q-TOF-MS have not been reported so far. In recent years, QE of A. capillaris based on multicomponents quantitative analysis has made some progress. Yu et al. developed a method to determine eight organic acids in A. capillaris extract by HPLC, including chlorogenic acid (CA), neochlorogenic acid (NCA), cryptochlorogenic acid (CCA), 1,3-dicaffeoylquinic acid (1,3-diCQA), 3,4-dicaffeoylquinic acid (3,4-diCQA), 3,5-dicaffeoylquinic acid (3,5-diCQA), 4,5-dicaffeoylquinic acid (4,5-diCQA), and caffeic acid [11]. Tian et al. established a quantitative analysis method of six organic acids of NCA, CA, CCA, 1,3-diCQA, 3,4-diCQA, and 4,5-diCQA in A. capillaris and its decoction by HPLC [12]. Thirteen components including four organic acids, four flavonoids, four coumarins, and one other of p-hydroxyacetophenone and ten components including four organic acids, five flavonoids, and one coumarin of scoparone in A. capillaris were determined by the same method, respectively [13, 14]. However, a comprehensive QE method for A. capillaris has not been established so far. Therefore, the aim of this work was to establish a new method for the QE of A. capillaris comprehensively based on qualitative analysis of the HPLC fingerprint and ultrafast liquid chromatography- (UFLC-) Q-TOF-MS/MS combined with quantitative analysis of multicomponents.

2. Experimental

2.1. Chemicals and Reagents

Reference substance of p-hydroxyacetophenone (no. 111897–201602, with purity ≥99.9%) was purchased from the National Institutes for Food and Drug Control (Beijing, China). 1-caffeoylquinic acid (1-CQA, no. CHB170525), NCA (no. CHB170914), CA (no. CHB170713), caffeic acid (no. CHB160907), CCA (no. CHB170828), 1,3-diCQA (no. CHB160620), rutin (no. CHB170303), hyperoside (no. CHB160904), isoquercetin (no. CHB160912), 3,4-diCQA (no. CHB160725), 3,5-diCQA (no. CHB171013), and 4,5-diCQA (No. CHB160726) were purchased from the Chengdu Chroma Biotechnology Co., Ltd. (Chengdu, China) (all with purity ≥98%). Methanol (HPLC grade) and acetonitrile (LC/MS grade) were purchased from Fisher Scientific (Fair Lawn, NJ, USA). Purified water was purchased from Wahaha Group Co., Ltd. (Hangzhou, China). Formic acid (HPLC grade) was supplied by Nanjing Chemical Reagent Co. Ltd. (Nanjing, China).

2.2. Apparatus

Determination of the HPLC fingerprint and the contents of 13 components were performed on a HPLC system (Waters Corp., Milford, MA, USA), equipped with a Waters e2695 separation unit, a Waters 2998 PDA detector, and an Empower 3 data processing system. Chromatographic separation was performed on a Symmetry C₁₈ column (4.6 mm × 250 mm, 5 μm, Waters Corp., USA). Acetonitrile (A) and 0.1% () formic acid (B) were used as mobile phases with the following gradient elution: 0−35 min, 5−10% A; 35−65 min, 10−25% A; 65−67 min, 25−90% A; and 67−80 min, 90% A. The flow rate was set at 1.0 mL/min, and the column temperature was maintained at 30°C. The injection volume of sample solution was 30 µL. The detection wavelength of fingerprint and content of p-hydroxyacetophenone, rutin, hyperoside, and isoquercetin was set at 254 nm and that of content of nine organic acids was set at 324 nm.

Identification of the common peaks in the HPLC fingerprint was performed on a UFLC-Q-TOF-MS/MS system. Separation was performed on a UFLC system (Shimadzu, Kyoto, Japan) by using a Symmetry C₁₈ column (250 mm × 4.6 mm, 5 μm); with the same mobile phases and the same gradient conditions abovementioned, the injection volume of the mixed reference substances solution for qualitative analysis and sample solution was all 20 µL. After separation, mass spectra were acquired on the AB Triple TOF 4600 plus system (AB SCIEX, Framingham, USA) with the following mass spectrometric parameters: ion source, DuoSpray; ESI mode, negative; ion source temperature, 550°C; ion spray voltage, −4500 V; nebulizer gas (gas 1), 60 psi; heater gas (gas 2), 60 psi; and curtain gas (CUR), 35 psi. The TOFMS-IDA-10MS/MS information acquisition method was used to obtain mass spectrometry information, and the parameters were set as follows: decluster potential (DP) of −80 V, collision energy (CE) of −10 eV, accumulation time of 250 ms, mass range of 105–1500 Da for the TOF-MS scan, collision energy (CE) of −35 eV, collision energy spread (CES) of 15 eV, and mass range of 50–1500 Da for the TOF-MS/MS detection. LC-MS/MS data were analyzed using PeakView mass spectrometry analysis software (Version 1.6, AB SCIEX, USA).

2.3. Samples and Sample Preparation

Information on all 31 batches of samples is given in Table 1, among which, 30 batches of A. capillaris (S1–S30) were purchased from different large TCM hospitals in China and authenticated as the dried aerial part of A. capillaris by the chief Chinese pharmacist Xudong Gong, the director of the Nantong Food and Drug Supervision and Inspection Centre. Herbal reference substance of A. capillaris (S31) was purchased from the National Institutes for Food and Drug Control (Beijing, China) in 2018.

Table 1: Samples information and similarities.

Sample no.
Manufacturers
Batch no.
Origins of herb
Similarity

S1
Nantong Sanyue Herbal Pieces Co., Ltd.
171208
Henan
0.949

S2
Nantong Sanyue Herbal Pieces Co., Ltd.
180109
Henan
0.993

S3
Nantong Sanyue Herbal Pieces Co., Ltd.
151110
Henan
0.996

S4
Nantong Sanyue Herbal Pieces Co., Ltd.
180308
Henan
0.905

S5
Suzhou Tianling Herbal Pieces Co., Ltd.
180205
Jiangsu
0.958

S6
Suzhou Tianling Herbal Pieces Co., Ltd.
180205010
Jiangsu
0.963

S7
Suzhou Tianling Herbal Pieces Co., Ltd.
170902010
Jiangsu
0.980

S8
Suzhou Tianling Herbal Pieces Co., Ltd.
180205015
Jiangsu
0.969

S9
Suzhou Tianling Herbal Pieces Co., Ltd.
160309010
Jiangsu
0.963

S10
Suzhou Tianling Herbal Pieces Co., Ltd.
160122010
Jiangsu
0.990

S11
Yancheng Herbal Pieces Co., Ltd.
2017091402
Jiangsu
0.986

S12
Anhui Bozhou Qiancao Guoyao Co., Ltd.
1712176
Shanxi
0.991

S13
Anhui Wansheng Herbal Pieces Co., Ltd.
171201
Shanxi
0.994

S14
Anhui Wansheng Herbal Pieces Co., Ltd.
180302
Shanxi
0.928

S15
Anhui Mengshi Herbal Pieces Co., Ltd.
170401
Anhui
0.961

S16
Bozhou Qiaocheng Wanshixiang Herbal Pieces Co., Ltd.
170901
Shanxi
0.970

S17
Anhui Xiehecheng Pharmaceutical Herbal Pieces Co., Ltd.
17051814
Shanxi
0.986

S18
Anhui Shenghaitang Herbal Pieces Co., Ltd.
2017080421
Shanxi
0.991

S19
Hebei Kaida Pharmaceutical Co., Ltd.
20171201
Hebei
0.987

S20
Zhejiang Tongjuntang Herbal Pieces Co., Ltd.
170921
Shaanxi
0.996

S21
Zhengzhou Ruilong Pharmaceutical Co., Ltd.
17110102
Henan
0.990

S22
Hebei Renxin Pharmaceutical Co., Ltd.
21118001
Hebei
0.983

S23
Shaohuatang Guoyao Co., Ltd.
171010
Shanxi
0.975

S24
Shanghai Wanshicheng Guoyao Products Co., Ltd.
180418-1
Shandong
0.934

S25
Shanghai Kangqiao Herbal Pieces Co., Ltd.
171125
Shaanxi
0.972

S26
Yancheng Herbal Pieces Co., Ltd.
2016030202
Jiangsu
0.994

S27
Hangzhou Huadong Herbal Pieces Co., Ltd.
1601118
Shandong
0.953

S28
Bozhou Yonggang Herbal Pieces Co., Ltd.
15113001
Shanxi
0.991

S29
Bozhou Yonggang Herbal Pieces Co., Ltd.
15070901
Shanxi
0.994

S30
Yunnan Baiyao Herbal Medicine Branch of Yunnan Group Co., Ltd.
YP20140601
Hubei
0.983

S31
National Institutes for Food and Drug Control
121555-201101
Unknown
0.968

The samples were dried at 40°C, ground into powder, and then sieved through a 40-mesh screen. Approximately 0.2 g of sample powder was accurately weighed and placed in a 50 mL dark brown volumetric flask. Approximately 49 mL of 50% () methanol was added and extracted by ultrasonication (200 W, 53 kHz) for 30 min. After cooling to room temperature, 50% () methanol was added for calibration of the volumetric flask and shaken well. The extract was filtered through a 0.22 μm filter membrane, and the filtrate was taken as the sample solution.

2.4. Preparation of Reference Substance Solutions

Appropriate amounts (5–20 mg) of 13 reference substances were accurately weighted, dissolved with 50% () methanol, respectively, and 13 reference substance stock solutions were prepared.

The mixed reference substances solution for qualitative analysis with a concentration range of 0.4–50 μg/mL of each compound was prepared by accurately absorbing appropriate volume of 13 reference substance stock solutions, mixing them, and diluting the mixture with 50% () methanol.

Working solution A for quantitative analysis was prepared by the same method as the mixed reference substances solution for qualitative analysis, and the final concentrations of 13 reference substances were at the range of 3.1–193 μg/mL. Working solution A was diluted two, five, and ten times with 50% () methanol to prepare working solutions B, C, and D, respectively.

2.5. Method Validation of the HPLC Fingerprint Analysis

The method of HPLC fingerprint determination was validated with precision, stability, and repeatability tests, by using peak 5 (CA) as the reference peak and the relative standard deviation (RSD) value of the average relative retention time (RRT) and relative peak area (RPA) of the 20 common peaks as measure values. In the precision test, six consecutive injections of the same sample (S1) solution were analyzed. Stability was examined by analyzing the sample solution (S1) at 0, 6, 12, 18, 24, and 36 h after preparation. Repeatability was examined by determination of six sample solutions prepared in parallel from S1.

2.6. Method Validation of the Quantitative Analysis

The method of quantitative analysis was validated with investigation of linear relationships, limit of quantitation (LOQ), limit of detection (LOD), precision, stability, repeatability, and the recovery test of 13 components. Investigation of linear relationships was performed by precisely injecting working solutions B, C, and D 10 μL and working solution A 10, 20, 30, and 40 μL into the HPLC systems for the calculation of the regression equations, correlation coefficients, and linear ranges of 13 components. Working solution D was successively diluted with 50% () methanol to give different concentrations of reference substance solutions. The LOQ and LOD values were determined by using signal-to-noise ratios of 3 : 1 and 10 : 1 and injecting 10 μL of above different concentrations of reference substance solutions. By using the RSDs of the peak areas of the 13 components as the measurement values, intraday precision, interday precision, and stability tests were performed, respectively. In the intraday precision test, six consecutive injections of 30 μL working solution A were analyzed, and in the interday precision test, six injections of 30 μL working solution A were analyzed twice a day over three consecutive days. Stability was examined by analyzing the peak areas of nine organic acids at 324 nm and four others at 254 nm detected in Section 2.5 of the stability test. Repeatability was examined by calculating the contents of 13 components according to the peak areas of nine organic acids at 324 nm and four others at 254 nm detected in Section 2.5 of the repeatability test and using the RSDs of the contents as the measured values. In the recovery test, approximately 0.1 g of S1 powder was weighed precisely, and then, 13 reference substance stock solutions were added to the sample in a certain volume according to the approximate proportion of the sample content to the reference substance (1 : 1) to prepare six sample solutions in parallel. The six sample solutions were injected into HPLC, and the average recovery rates and RSDs of the 13 components were calculated.

We followed the methods of Author links open overlay panel [15].

3. Results and Discussion

3.1. Method Validation of the HPLC Fingerprint Analysis

The RSDs of RRT and RPA for precision were less than 0.10% and 4.4%, those of stability were no more than 0.08% and 4.7%, and those of repeatability did not exceed 0.08% and 4.8%, respectively. The results met the national standards of TCM fingerprinting [16].

3.2. Method Validation of the Quantitative Analysis

As given in Table 2, the high correlation coefficient values (R² ＞ 0.9998) displayed good linearity over a wide range of injected amounts, and as given in Table 3, the RSDs of the intraday precision, interday precision, stability, and repeatability were all less than 5%, and the average recovery rates were in the range of 95.49%–103.20% with RSD values ranging 0.90–4.95%. The above results met the requirements of drug quality standard analysis method in Chinese Pharmacopoeia [17].

Table 2: Results of the investigation of the linear relationship, LOD, and LOQ.

Reference substance
Regression equation
R²
Linear range (ng)
LOD (ng)
LOQ (ng)

1-CQA
Y = 2231204X − 8098
0.9999
13.35 ∼ 534
1.60
5.34

NCA
Y = 2830658X − 5170
0.9999
5.15 ∼ 206
0.34
1.72

CA
Y = 2870573X − 117405
0.9999
192.3 ∼ 7692
1.54
7.69

Caffeic acid
Y = 4958993X − 7629
0.9998
1.90 ∼ 76.05
0.30
1.52

CCA
Y = 2656572X − 12630
0.9998
7.66 ∼ 306.24
0.51
2.55

p-Hydroxyacetophenone
Y = 2885362X − 7875
0.9999
3.05 ∼ 121.92
0.41
1.63

1,3-DiCQA
Y = 2995412X − 1885
0.9999
1.77 ∼ 70.84
0.24
1.18

Rutin
Y = 1638734X − 1384
0.9999
2.53 ∼ 101
0.40
1.68

Hyperoside
Y = 2406676X − 5708
0.9999
8.31 ∼ 332.4
0.33
1.66

Isoquercetin
Y = 1973858X − 1855
0.9999
2.90 ∼ 116
0.23
1.74

3,4-DiCQA
Y = 2669900X − 7344
0.9999
5.04 ∼ 201.6
0.67
2.69

3,5-DiCQA
Y = 3267110X + 5860
0.9999
122.30 ∼ 4892
1.73
3.46

4,5-DiCQA
Y = 2863719X − 7095
0.9999
13.65 ∼ 546
1.09
5.46

Table 3: Results of precision, stability, repeatability, and recovery tests (n = 6).

Components
Precision RSD (%)
Stability RSD (%)
Repeatability (RSD, %)
Recovery

Intraday
Interday
Mean (%)
RSD (%)

1-CQA
0.51
0.37
0.71
2.16
101.23
2.11

NCA
0.66
0.69
2.26
3.82
97.68
0.90

CA
0.53
0.52
0.26
4.17
96.19
3.09

Caffeic acid
0.73
0.78
1.14
1.17
97.41
2.59

CCA
0.58
0.49
1.03
3.93
99.66
4.89

p-Hydroxyacetophenone
0.67
0.70
1.20
1.83
97.15
3.00

1,3-DiCQA
0.72
0.76
2.30
3.64
95.49
4.78

Rutin
2.84
0.92
3.59
2.22
96.68
4.32

Hyperoside
0.65
0.56
0.35
3.97
95.75
4.77

Isoquercetin
0.86
0.78
2.85
4.06
98.47
4.95

3,4-DiCQA
0.62
0.62
4.69
1.16
103.20
4.85

3,5-DiCQA
0.62
0.65
0.71
4.02
98.96
3.75

4,5-DiCQA
0.60
0.61
0.53
3.81
96.83
4.82

3.3. Establishment of the HPLC Fingerprint and Similarity Analysis

31 batches of A. capillaris samples were determined (chromatograms are shown in Figure 1). The chromatographic data of the samples were imported into the software of Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine (version 2012, Chinese Pharmacopoeia Commission, Beijing, China). Using the chromatogram of S1 as a reference, the reference chromatogram was generated, and 20 peaks were extracted to be the common peaks (shown in Figure 1). The similarities between sample chromatograms and reference chromatogram were calculated by the above software, and the results showed that the similarities of 31 batches of A. capillaris were all greater than 0.9 (Table 3).

Figure 1: Chromatograms of 31 batches of A. capillaris (S1–S31) and the reference chromatogram (R).

3.4. Identification of the Common Peaks by UFLC-Q-TOF-MS/MS

Since more information and higher identifiability of fragmentation was observed in the negative ion mode, it was chosen for MS analysis rather than the positive ion mode. First, total ion chromatograms of the A. capillaris sample and mixed reference substances (Figure 2) were extracted using PeakView mass spectrometry analysis software. Second, the mass spectral data and dissociative rules of the reference substances were summarized, and the law of the quasimolecular ion [M − H]⁻ and/or [M + Cl]⁻ that could be selected as the precursor ion for collision-induced dissociation fragmentation to produce MS/MS product ions spectra was revealed. Finally, the components of the total 20 common peaks in the HPLC fingerprint were identified by comparing the retention time, m/z of [M − H]⁻ and/or [M + Cl]⁻ and MS/MS fragmentation patterns with those of the reference substances or previous literature reports, combining with online retrieval of two compound database of PubChem (http://pubchem.ncbi.nlm.nih.gov) and ChemSpider (http://www.chemsipider. com). The mass spectral data are given in Table 4.

(a)

(b)

Figure 2: Total ion chromatogram of A. capillaris sample (a) and mixed reference substances (b) (negative ion mode).

Table 4: Identification of the common peaks in the A. capillaris fingerprint by UHLC-Q-TOF-MS/MS.

Peak no.
tR (min)
Formula
MS
MS/MSc
Identification
Types of compounds

Measured
Theoretical
Error (ppm)

1
13.525
C₁₆H₁₈O₉
353.0885a
353.0878
2.0
191.0573
1-CQAd
Organic acids

2
16.933
C₁₆H₁₈O₉
353.0885a
353.0878
2.0
191.0572, 179.0350, 135.0441, 353.0906
NCAd
Organic acids

389.0631b
389.0645
-3.6
353.090

3
20.198
C₁₉H₂₆O₁₁
465.1162b
465.1169
-1.5
465.1170, 135.0455, 429.1407, 329.0680, 293.0897
6′-O-Xylosyl-p-hydroxyacetophenone-4-O-β-D-glucoside
Others

4
22.909
C₂₂H₂₈O₁₄
515.1409a
515.1406
0.5
191.0561, 323.0768, 515.1426, 161.0241, 353.0868, 179.0343
1-O-(4′-O-β-D-Glucosyl caffeoyl) quinic acid or 1-O-(3′-O-β-D-glucosyl caffeoyl) quinic acid
Organic acids

5
27.281
C₁₆H₁₈O₉
353.0886a
353.0878
2.2
191.0577
CAd
Organic acids

6
30.533
C₉H₈O₄
179.0358a
179.0350
4.6
135.0456, 107.0505, 179.0348, 117.0340
Caffeic acidd
Organic acids

7
32.916
C₁₆H₁₈O₉
353.0883a
353.0878
1.4
173.0462, 191.0568, 179.0355, 135.0461, 353.0901
CCAd
Organic acids

389.0647b
389.0645
0.3
173.0457, 179.0354, 191.0568, 353.0885, 135.0456

8
39.703
C₈H₈O₂
135.0457a
135.0452
4.0
93.0354, 135.0457
p-Hydroxyacetophenonea
Others

9
45.515
C₂₇H₃₀O₁₅
593.1535a
593.1512
3.9
593.1553, 353.0674, 473.1101, 383.0784, 503.1209, 413.0927
Apigenin 6, 8-di-C-β-D-glucoside
Flavonoids

10
46.316
C₂₅H₂₄O₁₂
515.1201a
515.1195
1.2
191.0566, 179.0356, 335.0887, 515.1225, 135.0461, 173.0463, 161.0243
1, 3-DiCQAd
Organic acids

551.0970b
551.0962
1.5
353.0893, 515.1234, 191.0568, 179.0357, 335.0785, 173.0443, 135.0461

11
48.753
C₂₇H₃₀O₁₆
609.1456a
609.1461
-0.8
609.1480, 463.0192, 447.0915, 301.0339
Isomer of rutin
Flavonoids

645.1207b
645.1228
-3.2
609.1482, 463.0906, 447.0931, 301.0316

12
55.161
C₂₇H₃₀O₁₆
609.1475a
609.1461
2.3
609.1516, 301.0362
Rutind
Flavonoids

13
55.657
C₂₁H₂₀O₁₂
463.0890a
463.0882
1.7
463.0914, 301.0359
Hyperosided
Flavonoids

14
56.590
C₂₁H₂₀O₁₂
463.0896a
463.0882
3.0
463.0937, 301.0373, 179.0010
Isoquercetind
Flavonoids

15
57.238
C₂₁H₂₀O₁₁
447.0945a
447.0933
2.7
285.0404, 447.0940
Kaempferol-3-O-glucoside
Flavonoids

16
57.638
C₂₇H₃₀O₁₅
593.1510a
593.1512
-0.3
593.1525, 285.0469
Kaempferol-3-O-rutinoside
Flavonoids

17
61.037
C₂₁H₂₀O₁₁
447.0939a
447.0933
1.4
447.0974, 285.0420
Quercetin-3-O-rhamnoside
Flavonoids

483.0705b
483.0700
1.1
447.0954, 285.0406

18
61.495
C₂₅H₂₄O₁₂
515.1220a
515.1195
4.9
191.0579, 353.0917, 179.0364 515.1287
3, 4-DiCQAd
Organic acids

19
61.913
C₂₅H₂₄O₁₂
515.1212a
515.1195
3.3
191.0572, 353.0909, 179.0353, 173.0456, 135.0454, 515.1298
3, 5-DiCQAd
Organic acids

20
64.996
C₂₅H₂₄O₁₂
515.1215a
515.1195
3.9
173.0462, 353.0913, 179.0356, 515.1294, 191.0572, 135.0448
4, 5-DiCQAd
Organic acids

Quasimolecular ion was [M-H]⁻. bQuasimolecular ion was [M + Cl]⁻. cSequencing according to the abundance. dConfirmed by comparison with reference substances.

Among 20 components, 13 ones were unambiguously identified by comparison with the reference substances, including nine organic acids such as 1-CQA (peak 1), NCA (peak 2), CA (peak 5), caffeic acid (peak 6), CCA (peak 7), 1,3-diCQA (peak 10), 3,4-diCQA (peak 18), 3,5-diCQA (peak 19), and 4,5-diCQA (peak 20), three flavonoids such as rutin (peak 12), hyperoside (peak 13), and isoquercetin (peak 14), and one other p-hydroxyacetophenone (peak 8).

For peak 3, the molecular formula of C₁₉H₂₆O₁₁ was speculated by software, and its quasimolecular ion was at an m/z of 465.1162 ([M + Cl]⁻). No literature reported the compounds with the molecular formula of C₁₉H₂₆O₁₁ in A. capillaris so far. Sixty-nine and twenty-seven compounds consistent with this formula were retrieved from PubChem and ChemSpider, respectively. The structures of these compounds were analyzed one by one by the exclusion method, combined with p-hydroxyacetophenone and 6′-O-dicaffeoyl-p- hydroxyacetophenone-4-O-β-D-glucoside, and another compound with same parent nucleus [18], existed in A. capillaris; peak 3 was temporarily identified as 4-acetylphenyl 6-O-β-D-xylosyl-β-D-glucoside (6′-O-xylosyl-p-hydroxyacetophenone-4-O-β-D-glucoside), the first compound in both databases. In MS/MS spectrum of this compound, m/z of 465.1170, 429.1407, 329.0680, 293.0897, and 135.0455 were determined, which was corresponded to [M + Cl]⁻, [M-H]⁻, [M + Cl]⁻ loss of p-hydroxyacetophenone (C₈H₈O₂), [M − H]⁻ loss of C₈H₈O₂, and [M − H]⁻ loss of xylose-glucosyl (C₁₁H₁₈O₉), respectively.

According to literature [19], the component of peak 4 was identified as a caffeoylquinic acid glucoside. The quasimolecular ion of this component was at an m/z of 515.1409 ([M − H]⁻), and the MS/MS fragment ions were determined as an m/z of 515.1426 corresponding to [M-H]⁻, an m/z of 353.0868 corresponding to [515-C₆H₁₀O₅ (glucosyl)]⁻, an m/z of 323.0768 corresponding to [515-C₇H₁₂O₆ (quinic acid)]⁻, an m/z of 191.0561 corresponding to [353-C₉H₆O₃ (caffeyl)]⁻, an m/z of 179.0343 corresponding to [353-C₇H₁₀O₅ (residue of quinic acid)]⁻, and an m/z of 161.0241 [353-C₇H₁₂O₆]⁻. The linkage position between caffeoyl and quinic acid could be distinguished based on the MS² fragmentation; when this position was at 1-OH, 3-OH, or 5-OH, the m/z of 191 was the base peak; while linkage position was at 4-OH, the m/z of 173 was the base peak [19]. An m/z of 191 was determined as the base peak of peak 4, so the connection position of 4-OH was excluded. The relative intensity of m/z 179 fragment ion could also be used to determine the linkage position between caffeoyl and quinic acid [19]. The relative intensity of m/z 179 fragment ion of peak 4 was determined as 5.62%, the one of 1-CQA (peak 1) and NCA (peak 2, linkage position was at 5-OH) was determined as 6.06% and 55.28%, respectively, and fragment ion of m/z 179 was not detected in CA (peak 5, linkage position was at 3-OH). Therefore, the component of peak 4 was temporarily identified as 1-O-(4′-O-β-D-glucosyl caffeoyl) quinic acid or 1-O-(3′-O-β-D-glucosyl caffeoyl) quinic acid, which was first detected in A. capillaris, to the best of our knowledge.

The component of peak 9 was a typical flavone di-C-glucoside, according to the analysis of detected mass spectrometry data and literature [20]. The quasimolecular ion of this component was determined as an m/z of 593.1535 ([M-H]⁻), and the MS/MS fragment ions were m/z of 593.1553, 503.1209, 473.1101, 413.0927, 383.0784, and 353.0674, which were consistent with the mass spectrum data of apigenin 6,8-di-C-β-D-glucoside reported in the literature [20], and its possible dissociation pathway is shown in Figure 3. To the best of our knowledge, this component was also first detected in A. capillaris.

Figure 3: The possible dissociation pathway of the component of peak 9.

The component of peak 11 was identified as the isomer of rutin according to literature [21]. Its quasimolecular ion was determined as an m/z of 609.1456 ([M-H]⁻) and an m/z of 645.1207 ([M + Cl]⁻), and its MS/MS fragment ions were m/z of 609.1480, 447.0915, and 301.0339, which correspond to [M-H]⁻, [609-glucosyl]⁻, and [609-C₁₂H₂₀O₉ (rutinose)]⁻, respectively.

The components of peak 15, 16, and 17 were temporarily identified as three flavonoids of kaempferol-3-O-glucoside, kaempferol-3-O-rutinoside (nicotiflorin), and quercetin-3-O-rhamnoside [22, 23], respectively. The quasimolecular ions of peak 15 were at m/z of 447.0945 ([M-H]⁻), the ones of peak 16 were determined as m/z of 593.1510 ([M-H]⁻), and the ones of peak 17 were determined as m/z as 447.0939 ([M-H]⁻) and 483.0705 ([M + Cl]⁻). The MS/MS fragment ions of peak 15 were m/z of 447.0940 due to [M-H]⁻ and 285.0404 due to [M-H-glucosyl]⁻, the ones of peak 16 were m/z of 593.1525 and 285.0469, and the ones of peak 17 were m/z of 447.0954 and 285.0420.

The structures or possible structures of the components of peaks 1–8 and peaks 10–20 are shown in Figure 4.

Figure 4: Structures or possible structures of the components of peaks 1–8 and peaks 10–20.

3.5. Wavelength Selection for Quantitative Analysis of 13 Components

It was found that all 13 components could be detected at 254 nm, but the peak of 3,4-diCQA (peak 18) has not been completely separated from the nearby ones; organic acids had strong absorption near 324 nm, but there was almost no absorption of p-hydroxyacetophenone (peak 8) at this wavelength. Therefore, 324 nm was selected as the detection wavelength for nine organic acids, and 254 nm was selected for other four components. The chromatograms of the mixed reference substances and sample are shown in Figure 5.

(a)

(b)

Figure 5: HPLC chromatograms of the mixed reference substances (a) and A. capillaris sample (b). The number of peaks is the same as Table 4.

3.6. Contents of 13 Components in 31 Batches of A. capillaris

As given in Table 5 and Figure 6, there were some differences in the contents of 13 components in different samples, which is basically consistent with the previous literature reports [12–14]; however, the content of CA seems to have a certain correlation with the other 12 components and the total of 13 components. Therefore, the bivariate correlation analysis method in SPSS 20 statistical software was used to analyze the correlation between the contents of CA and the contents of 12 other components and the total content of all 13 components in 31 batches of A. capillaris. As the results given in Table 6, the contents of 10 components and the total content of 13 components were significantly correlated with the content of CA ( or ), except for the content of caffeic acid and 1,3-diCQA, which had poor correlation with the content of CA (). According to the data in Table 5, the average contents of caffeic acid and 1,3-diCQA in 31 batches of samples only account for 1.10% and 0.92% of the average contents of all 13 components, respectively, so these two components can be ignored to a certain extent. According to the above analysis, the content of other components in different batches of A. capillaris is obviously related to the content of CA, that is to say, the content of CA largely reflects the quality of A. capillaris. Therefore, CA can be regard as the quality marker of A. capillaris. CA is the content determination component of A. capillaris in Chinese Pharmacopoeia. It is suggested that hospitals, pharmacies, and pharmaceutical manufacturers purchase multiple batches of A. capillaris and mix the high and low CA content batches before use according to the CA detection report provided by the supplier, so as to ensure clinical safety and effectiveness.

Table 5: The contents of the 13 components in 31 batches of A. capillaris (mg/g).

No.
1-CQA
NCA
CA
Caffeic acid
CCA
p-Hydroxyacetophenone
1, 3-DiCQA
Rutin
Hyperoside
Isoquercetin
3, 4-DiCQA
3, 5-DiCQA
4, 5-DiCQA
Total

S1
1.357
0.197
8.575
0.236
0.358
0.389
0.130
0.150
0.556
0.299
0.279
5.857
1.564
19.946

S2
1.175
0.248
7.646
0.216
0.430
0.337
0.153
0.099
0.390
0.274
0.451
5.038
1.743
18.199

S3
1.076
0.247
7.601
0.242
0.396
0.367
0.124
0.132
0.506
0.364
0.390
6.015
2.023
19.482

S4
1.007
0.259
5.369
0.194
0.417
0.709
0.398
0.086
0.200
0.101
0.348
4.575
1.986
15.649

S5
0.632
0.144
3.124
0.202
0.259
0.174
0.180
0.071
0.126
0.103
0.241
2.834
1.153
9.242

S6
0.600
0.150
3.177
0.199
0.266
0.186
0.169
0.065
0.124
0.100
0.173
2.655
1.170
9.036

S7
0.861
0.153
4.258
0.207
0.269
0.301
0.074
0.092
0.279
0.225
0.181
2.778
1.155
10.832

S8
0.680
0.161
3.463
0.214
0.287
0.165
0.191
0.078
0.133
0.103
0.258
3.139
1.353
10.225

S9
0.446
0.154
3.535
0.232
0.255
0.147
0.056
0.062
0.242
0.170
0.203
2.880
1.132
9.515

S10
0.990
0.223
7.134
0.251
0.373
0.330
0.059
0.085
0.453
0.334
0.298
4.335
1.522
16.388

S11
1.271
0.268
6.936
0.190
0.444
0.827
0.332
0.106
0.259
0.108
0.417
5.561
1.929
18.647

S12
1.043
0.246
5.317
0.189
0.435
0.511
0.117
0.078
0.282
0.150
0.343
4.370
1.910
14.992

S13
0.658
0.140
5.505
0.086
0.284
0.236
0.059
0.136
0.276
0.122
0.254
3.952
0.948
12.656

S14
0.897
0.229
7.479
0.103
0.510
0.317
0.103
0.108
0.351
0.114
0.289
5.095
1.645
17.241

S15
0.647
0.129
3.402
0.113
0.225
0.365
0.105
0.085
0.130
0.075
0.186
2.407
0.952
8.820

S16
0.555
0.101
3.704
0.095
0.217
0.246
0.056
0.097
0.158
0.085
0.109
2.462
0.674
8.556

S17
1.189
0.150
7.572
0.112
0.262
0.379
0.057
0.122
0.561
0.251
0.257
4.794
1.013
16.718

S18
0.630
0.145
4.387
0.086
0.271
0.259
0.106
0.126
0.178
0.081
0.243
3.825
1.202
11.536

S19
1.072
0.150
4.875
0.208
0.282
0.151
0.069
0.063
0.150
0.099
0.269
4.574
1.178
13.139

S20
0.962
0.205
6.458
0.099
0.380
0.510
0.132
0.090
0.267
0.110
0.343
5.388
1.548
16.493

S21
1.065
0.245
6.018
0.188
0.426
0.338
0.093
0.116
0.361
0.179
0.527
6.191
2.155
17.902

S22
0.929
0.283
7.567
0.085
0.502
0.265
0.078
0.108
0.217
0.106
0.558
7.919
2.066
20.683

S23
0.550
0.171
4.541
0.096
0.265
0.296
0.060
0.106
0.273
0.142
0.129
2.844
0.803
10.276

S24
1.028
0.195
6.168
0.132
0.345
0.521
0.170
0.120
0.311
0.146
0.340
5.419
1.521
16.416

S25
1.272
0.164
6.073
0.139
0.278
0.125
0.333
0.079
0.205
0.151
0.459
4.780
1.299
15.356

S26
0.810
0.177
5.326
0.123
0.356
0.307
0.098
0.133
0.246
0.100
0.269
4.962
1.426
14.334

S27
0.783
0.117
3.359
0.157
0.210
0.104
0.173
0.090
0.145
0.090
0.246
3.141
0.952
9.568

S28
0.879
0.296
6.849
0.206
0.476
0.437
0.104
0.167
0.532
0.211
0.502
6.732
2.456
19.847

S29
0.796
0.203
5.721
0.135
0.261
0.273
0.099
0.132
0.509
0.227
0.297
4.595
1.162
14.411

S30
0.862
0.159
4.057
0.141
0.239
0.352
0.245
0.066
0.176
0.093
0.246
3.280
1.208
11.123

S31
1.379
0.171
11.377
0.079
0.381
0.341
0.017
0.060
0.288
0.144
0.285
6.786
0.815
22.124

Average
0.907
0.190
5.696
0.160
0.334
0.331
0.134
0.100
0.287
0.157
0.303
4.490
1.408
14.495

Figure 6: The bar graph of contents of 13 components in 31 batches of A. capillaris.

Table 6: Bivariate correlation analysis results of the correlation between the contents of CA and 12 other components and the total of all 13 components in 31 batches of A. capillaris.

Component
Correlation coefficient of Spearson

1-CQA
0.748
0.0001

NCA
0.665
0.0001

Caffeic acid
−0.340
0.856

CCA
0.698
0.0001

p-Hydroxyacetophenone
0.529
0.002

1,3-DiCQA
−0.160
0.390

Rutin
0.444
0.012

Hyperoside
0.797
0.0001

Isoquercetin
0.650
0.0001

3,4-diCQA
0.696
0.0001

3,5-diCQA
0.861
0.0001

4,5-diCQA
0.498
0.005

Total of 13
0.942
0.0001

4. Conclusion

In this study, a new method was developed for the comprehensive QE of A. capillaris based on qualitative analysis of the HPLC fingerprint and UFLC-Q-TOF-MS/MS combined with quantitative analysis of multicomponents. The results showed that there were 20 common peaks in the HPLC fingerprints of A. capillaris. The similarities between the sample chromatograms and reference chromatogram were good. The components of the 20 common peaks were identified as ten organic acids, eight flavonoids, and two others. Among nine organic acids such as 1-CQA, NCA, CA, caffeic acid, CCA, 1,3-diCQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA, three flavonoids such as rutin, hyperoside, and isoquercetin, and one other p-hydroxyacetophenone, a total of 13 components were unambiguously identified by comparison with reference substances; one caffeoylquinic acid glucoside of 1-O-(4′-O-β-D-glucosyl caffeoyl) quinic acid or 1-O-(3′-O-β-D-glucosyl caffeoyl) quinic acid and one flavone di-C-glucoside of apigenin 6,8-di-C-β-D-glucoside were detected in A. capillaris for the first time. There were some differences in the contents of 13 components in different samples; chlorogenic acid could be regarded as the quality marker of A. capillaris. In summary, the method established in the present study can be used for the comprehensive QE of A. capillaris and can also provide reference for QE of other HMs.

Data Availability

The data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Authors’ Contributions

Rongrong Zhou and Zhihua Dou contributed equally to this work.

Acknowledgments

The authors would like to acknowledge KeyResearch and Development (Social Development) Fund Project of Jiangsu Province, China (BE2018674), Traditional Chinese Medicine Science and Technology Plan Project of Jiangsu Province, China (YB201836), and Nantong Basic Research Project, Nantong, Jiangsu Province, China (JCZ20168).

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