Explanation for the erratum
1. The identification of unknown compound
1.1 Material
The unknown compound (Lot no. 13091831) was bought from Shanghai Tauto Biotech (Shanghai, China) on
November 22, 2013.
1.2 Mass spectrometric analysis method
A Thermo Scientific LTQ Orbitrap XL mass spectrometer was operated with an ESI source in negative ion mode
at 60 000 resolving power (defined as FWHM at m/z = 400) for full scan analysis (mass range 200–1000 u). The
normalized collision energy for MS/MS detection was set at 40%. Nitrogen was used as sheath gas and auxiliary
gas, and helium served as the collision gas. The key optimized ESI parameters were: source voltage: 4 kV;
sheath gas flow: 35 arb; auxiliary gas flow: 5 arb; capillary voltage: –40 V; capillary temperature: 300°C; tube
lens: –67 V.
1.3 Results
As shown in Fig. 1, the accurate mass of the unknown compound was 731.16119 [M-H]– and further MS2
analysis with 40% normalized collision energy resulted in the fragment ions at m/z 551, 533, 519, 339, 321 and
295, which all matched with the data of 9’’-methyl lithospermate B [1]. The molecular formula of 9’’-methyl
lithospermate B is C37H32O16 and its theoretical exact mass ([M-H]–) is 731.16121. The measured mass ([M-H]–)
was 731.16119 with only –0.03 ppm error compared with the theoretical exact mass ([M-H]–) of 9’’-methyl
lithospermate B. Moreover, the Corrected Product Certificates supported by Shanghai Tauto Biotech also
indicated that the compound was 9’’-methyl lithospermate B.
Therefore the unknown compound was identified and confirmed as 9’’-methyl lithospermate B.
9’’-Methyl lithospermate B (CAS no. 1167424-31-8) was also a phenolic constituent in Salvia species [1, 2] and
its chemical structure is shown in Fig. 2.
Unknown compound_141225 #33 RT: 0.46 AV:1
T: FTMS - c ESI Full ms [200.00-1000.00]
NL: 8.12E7
(A)
[M-H]731.16119
100
90
80
Relative Abundance
70
60
50
40
321.03937
30
295.06052 339.04996
20
533.10822
10
493.11386
361.03253
411.07196
269.08176
0
200
300
400
759.15436
829.13818
551.11914
500
701.15198
600
m/z
914.13690 965.67474
700
800
900
1000
MS/MS for 731.20 20 141225 # 683 RT: 2.40 AV: 1 NL: 2.86E5
T: ITMS - c ESI Full ms2 731.20@cid40.00 [200.00-1000.00]
533.11
100
(B)
321.03
519.09
90
80
Relative Abundance
70
60
50
40
30
294.99
20
10
339.02
551.14
279.17
219.03 249.06
0
200
357.06
250
300
350
411.19
400
457.18 475.14 507.17
450
620.93
500
550
600
m/z
Figure 1. ESI spectra of unknown compound. (A) Negative ion ESI mass spectrum with full scan. (B) CID
spectrum of [M–H]– ion (m/z 731.20),
OH
OH
OH
O
O
OH
HO
HO
O
O
OH
O
O
O
OH
O
Figure 2. Chemical structure of 9’’-methyl lithospermate B
2. The confirmatory of other six standard compounds
The other six phenolic standards were also confirmed by their UV spectrum and accurate mass. According to the
UV spectrum, shown in Fig. 3, the max absorptions of the six standards matched with references [3] and [4]. The
accurate masses are close to the theoretical values, which means that they can reflect the extract elemental
composition and details are indicated in Fig. 4 and Table 1.
(1)
(2)
(3)
(4)
(5)
(6)
Figure 3. UV spectra of the standard compounds. Protocatechuic aldehyde (1), salvianolic acid C (2), rosmarinic
acid (3), danshensu (4), salvianolic acid B (5), and protocatechuic acid (6).
Peak 1 Protocatechuic aldehyde_141225 #26 RT: 0.47 AV: 1 NL: 1.62E6
T: FTMS - c ESI Full ms [55.00-500.00]
Peak 2 Salvianolic acid C_141225 #75 RT: 1.14 AV: 1 NL: 8.96E6
T: FTMS - c ESI Full ms [50.00-1000.00]
（1）
130
120
[M-H]-
80
137.02426
100
70
Relative Abundance
Relative Abundance
90
80
70
60
50
40
60
219.17471
50
40
30
30
108.02183
20
20
103.07392
10
10
108.02163
60
70
80
90
100
110
m/z
Peak 3 Rosmarinic acid_141225 #121 RT: 1.89 AV: 1 NL: 3.65E7
T: FTMS - c ESI Full ms [50.00-1000.00]
120
130
140
150
100
197.04521
150
265.14746 311.05560
200
250
300
Peak 5 Danshensu_141225 #8 RT: 0.12 AV: 1 NL: 3.47E7
T: FTMS - c ESI Full ms [50.00-500.00]
197.04570
100
[M-H]-
（3）
90
70
70
Relative Abundance
80
60
50
40
161.02396
96.96960 135.04503
100
457.05365
422.07074
373.09195
473.07150 523.39276
313.07132
150
200
250
300
350
m/z
400
450
500
550
（5）
Relative Abundance
50
40
197.04510
200
350
400
（6）
50
219.17500
40
137.02454
265.14774
20
250.15659
815.12177
538.10681
588.85760
500
m/z
300
168.00658
519.09265
400
250
60
30
300
200
90
70
0
391.06863 417.08124
250.15784
150
153.01894 [M-H]-
100
60
100
227.05634
153.01962
135.04552
109.02976
100
70
493.11334
（4）
219.17552
650
80
10
[M-H]-
179.03540
0
600
80
321.03976
340.05365
650
40
10
[M-H]-
90
265.14737
600
Peak 7 Protocatechuic acid_141225 #97 RT: 1.84 AV: 1 NL: 5.68E6
T: FTMS - c ESI Full ms [50.00-1000.00]
717.14514
100
20
550
m/z
Peak 6 Salvianolic acid B_141225#125 RT: 1.80 AV: 1 NL: 2.51E7
T: FTMS - c ESI Full ms [50.00-1000.00]
30
500
50
20
197.04517
219.17491
450
60
30
30
10
400
90
80
20
519.09326
350
m/z
359.07642
100
Relative Abundance
137.02431
293.04504
139.02843
130.99263
0
Relative Abundance
（2）
90
110
0
[M-H]491.09769
100
600
10
745.13837
0
700
800
900
1000
109.02954
293.17905
315.03159
78.95914
100
336.88937
150
200
250
300
m/z
350
426.96472
400
450
504.98544
500
550
Figure 4. Negative ion ESI mass spectra of the standard compounds. Protocatechuic aldehyde (1), salvianolic
acid C (2), rosmarinic acid (3), danshensu (4), salvianolic acid B (5), and protocatechuic acid (6).
Table 1 The mass data of six components acquired by using LTQ-Orbitrap-XL
Analyte
Molecular
Theoretical exact
Measured mass
Error
formula
mass ([M-H]–, Da)
([M-H]–, Da)
(ppm)
CAS No.
Protocatechuic aldehyde
139-85-5
C7H6O3
137.0239
137.0242
2.19
Salvianolic acid C
115841-09-3
C26H20O10
491.0978
491.0977
–0.20
Rosmarinic acid
20283-92-5
C18H16O8
359.0767
359.0764
–0.84
Danshensu
76822-21-4
C9H10O5
197.0450
197.0457
3.55
Salvianolic acid B
121521-90-2
C36H30O16
717.1456
717.1451
–0.70
Protocatechuic acid
99-50-3
C7H6O4
153.0188
153.0189
0.65
References
[1] Zeng, G., Xiao, H., Liu, J., et al., Rapid Commun. Mass Spectrom. 2006, 20 (3), 499–506.
[2] Wu, Z., Ouyang, M., Yang, C., Acta Bot. Yunnanica 1999, 21 (4), 512–516.
[3] Li, Y., Qu, H., Cheng, Y., J. Pharm. Biomed. Anal. 2008, 47 (2), 407–412.
[4] Liu, M., Li, Y., Zhang, F., et al., J. Sep Sci. 2007, 30 (14), 2256–2267.