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1H And 13C-Nmr Spectral Data Of Compound Sxe15 And Reference Substance

13 C -NMR shows that it corresponds to the molecular formula C21H20O10 ( M = 432.1). Comparing the spectrum of compound SXE15 with the spectrum of compound SXE12, we see similarities except for the appearance of the sugar part. Specifically, the 1 H - NMR spectrum ( Table 3.14 ) of compound SXE15 shows the presence of the spin interaction system A2B2 characteristic of para-substituted protons belonging to ring B at δ H 6.93 (2H, d, J = 7.5 Hz) and 7.74 (2H, dd, J = 7.5 Hz). The AB spin interaction system was also shown at δ H 6.17 (1H, d, J = 2.0 Hz) and 6.42 (1H, d, J = 3.0 Hz) which is characteristic of the meta potential of the A ring. The appearance of an anomeric proton at δ H 5.39 (1H, d, J = 1.5 Hz) indicates the α- sugar configuration , in addition to a doublet proton signal of the methyl group at δ H 0.95 (1H, d, J = 6.0 Hz) indicating the presence of the α -rhamnose sugar. The 13 C-NMR spectrum ( Table 3.14 ) of compound SXE15 showed the presence of 18 carbon signals including a carbonyl group at δ C 179.4 which allowed the identification of the kaempferol skeleton and the α -rhamnopyranose sugar .

Combined with the HMBC spectrum showing the interaction between the anomeric proton at δ H 5.39 (1H, d, J = 1.5 Hz, H-1″) with C-3 ( δ C 136.1), allowing to confirm the glycosidic bond of the sugar with the aglycon at position C-3, the interactions of the proton in the B ring at δ H 7.74 (2H, d, J = 7.5 Hz) with C-2 ( δ C 158.3) indicate the bond of the B ring and the C ring at position C-2, comparison with reference [ 176] shows that compound SXE15 is kaempferol-3- O - α - rhamnopyranosid or afzelin ( Figure 3.22 ).

Table 3.14. 1 H and 13 C-NMR spectral data of compound SXE15 and reference material


C/H position

a,b

δ C

(ppm)

a*

δ C

(ppm) [ 176]

a,c

δ H

(ppm, Hz)

b*

δ H

(ppm, Hz) [ 176]

2

158.3

158.6



3

136.1

136.2



4

179.4

179.4



5

162.9

163.2



6

99.8

100.0

6.17 (1H, d; 2.0)

6.19 (1H, d; 2.4)

7

165.6

166.6



8

94.7

94.9

6.42 (1H, d; 2.0)

6.36 (1H, d; 2.2)

9

159.1

159.2



10

105.8

105.7



1'

122.6

122.6



2',6'

132.2

131.9

7.74 (2H, d; 7.5)

7.76 (1H, d; 8.8)

3',5'

116.4

116.5

6.93 (2H, d; 7.5)

6.93 (1H, d; 8.9)

4'

161.4

161.6



1''

103.4

103.5

5.39 (2H, d; 1.5)

5.36 (1H, d; 2.2)

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1H And 13C-Nmr Spectral Data Of Compound Sxe15 And Reference Substance

72.1

72.1

4.26 (1H, brs)

4.21 (1H, solution; 1.7; 3.42)

3″

72.9

72.0

3.75 (1H, t; 5.5)

3.71 (1H, m)

4″

73.2

73.2

3.36 (1H, m)

3.60 (1H, m)

5″

71.8

71.9

3.35 (1H, m)

3.47 (1H, m)

6″

17.6

17.7

0.95 (3H, d; 6.0)

0.91 (3H, d; 5.6)

a MeOD-d 6 , b 125MHz, c 500 MHz, a* DMSO-d 6 , 125 MHz, b* DMSO-d 6 , 500MHz

2″




Figure 3.22. Chemical structure of compound SXE15

* Compound SXE16

Compound SXE16 obtained has a bright yellow color, ESI-MS spectrum shows pseudomolecular ion peaks m/z 460.9 [M - H] ⁻ and m/z 485.0 [M + Na] ⁺, combined with 13 C-NMR spectrum shows that compound SXE16 corresponds to the molecular formula C22H22O11 ( M = 462.1 ) . Comparing the 1 H and 13 C -NMR spectra ( Table 3.15 ) of compound SXE16 with compound SXE10 , we see similarities except for the appearance of the sugar ring. Therefore, compound SXE16 may be a derivative of scutellarein. The appearance of anomeric proton signal at δ H 5.10 (1H, d, J = 4.7 Hz) allows predicting the presence of a sugar ring, compared with reference literature

[ 98] allows us to predict the presence of β sugar in the structure. The remaining proton signals of the sugar ring are in the range of δ H 3.21- 3.75 ppm. The 13 C-NMR spectrum ( Table 3.15 ) of compound SXE16 shows the presence of 13 carbon units, of which 4 carbons are characteristic of the para-substituted B ring, and 6 carbons of the A ring, the remaining 3 carbons of the C ring with the characteristic signal of the carbonyl group at δ C 182.3. In addition, 4 signals of the carbons of the sugar ring at δ C 73.2; 76.8; 69.6; 77.3; 60.3 and an anomeric carbon signal at δ C 100.2 allow us to confirm the presence of β -glucopyranose sugar in the molecule [ 98]. The binding positions of the substituents were determined based on the HMBC long-range interaction spectrum. In the spectrum, we see the interaction of the methoxy group at δ H 3.76 (3H, s, OCH 3 ) with δ C 132.6 (C-6), proving that the methoxy group is attached to the aglycon at the C-6 position of the derivative.

scutellarein. In addition, the change in the H-8 proton shift similar to other SXE10 structures allows us to confirm the glycosidic bond between β - glucopyranose and the aglycon at position C-7 and combined with reference [98] allows us to confirm that compound SXE16 is ispidulin-7- O - β- glucopyranoside ( Figure 3.23 ).

Table 3.15. 1 H and 13 C-NMR spectral data of compound SXE16 and reference substance


C/H position

a,b

δ C

(ppm)

a*

δ C

ppm [98]

a,c

δ H

(ppm, Hz)

2

164.5

164.6


3

102.3

102.6

7.00 (1H, s)

4

182.3

182.3


5

152.5

152.4


6

132.6

132.5


7

156.4

156.4


8

94.3

94.3

6.81 (1H, s)

9

152.2

152.1


10

105.7

105.7


1'

120.1

120.9


2',6'

128.6

128.6

7.92 (2H, d; 8.4)

3',5'

116.3

116.0

6.90 (2H, d, 8.8)

4'

162.7

161.0


5-OH



13.0 (1H, brs)

1''

100.2

101.0

5.10 (1H, d; 4.6)

2″

73.2

73.2

3.45-3.33 (m)

3″

76.8

77.3

3.45-3.33 (1H, m)

4″

69.6

70.4

3.21 (1H, t; 8.9)

5″

77.3

77.9

3.45-3.33 (1H, m)

6″

60.3

61.7

3.46 (1H, m); 3.75 (1H, d; 10.6)

3- OCH3

60.6

61.1

3.76 (3H, s)

a DMSO-d 6 , b 125 MHz, c 500 MHz, a* DMSO-d 6 , 125 MHz


Figure 3.23. Chemical structure of compound SXE16

* Compound SXE17

The obtained compound SXE17 has a bright yellow color, on the HR-ESI MS spectrum (positive) shows the appearance of pseudomolecular ion peak m/z 463.1232 [M + H] ⁺ , the HR-ESI MS spectrum (negative) also shows ion peaks m/z 461.1088 [M - H] ⁻ and m /z 497.0851 [M + Cl] ⁻ combined with the 13 C - NMR spectrum , showing that it is consistent with the molecular formula C22H22O11 ( M = 462.1162 ).

Comparison of the NMR spectra ( Table 3.16 ) of compound SXE17 with that of compound SXE16 shows similarities except for the difference in the sugar ring. The presence of anomeric proton signal at δ H 4.98 (d, J = 7.2 Hz, H-1″) indicates the presence of β sugar , the remaining proton signals belong to the sugar ring protons at δ H 3.25-3.70 ppm.

The 13 C-NMR spectrum ( Table 3.16 ) of the compound showed the presence of 20 carbon signals, of which 6 carbon signals belonged to the A ring at δ C 96.2; 99.5; 133.8; 153.4; 151.6 and 156.3, the signals at δ C 179.8; 160.8 and 102.8 belonged to the C ring, and the remaining signals belonged to the C ring.

B. From the above data, it is possible to confirm the presence of scutellarein derivatives. In addition, 5 signals appeared in the region from δ C 77.2-60.7 and one carbon signal at δ C 100.0, allowing to determine the presence of β -glucopyranose sugar in the molecule.

The HMBC spectrum of compound SXE17 showed the interaction of the anomeric proton signal at δ H 4.98 (1H, d, J = 7.5 Hz, H-1″) with carbon C-4′ ( δ C 159.6), which allowed us to determine the glycosidic bond position at the 4′-OH position of ring B. In addition, the binding position of ring B with ring C was determined through the interaction between proton H-2′,6′ ( δ H 7.90) with C-2 ( δ C 160.8) of ring C. The interaction of methoxy proton ( δ H 3.65) with carbon C-6 ( δ C 133.8), which indicated that the methoxy group was attached to the C-6 position of scutellarein [ 83 ]. Therefore, compound SXE17 was identified as hispidulin-4′- O - β -glucopyranoside ( Figure 3.24 ). Table 3.16. 1 H and 13 C-NMR spectral data of compound SXE17 and reference substance

C/H position

a,b

δ C

(ppm)

a*

δ C

(ppm) [83]

a,c

δ H

(ppm, Hz)

2

160.8

162.0


3

102.8

103.4

6.54 (1H, s)

4

179.8

181.9


5

151.6

152.4


6

133.8

132.0


7

156.3

157.7


8

96.2

94.5

6.05 (1H, s)

153.4

152.8


10

99.5

101.8


1'

125.0

124.2


2',6'

127.5

128.1

7.90 (2H, d; 8.9)

3',5'

116.6

116.7

7.15 (2H, d; 8.9)

4'

159.6

160.4


5-OH



12.78 (1H, brs)

1''

100.0

99.8

4.98 (1H, d; 7.5)

2″

73.3

73.3

3.38-3.27 (2H, m)

3″

77.2

76.3

4″

69.7

69.7

3.19 (1H, t; 9.0)

5″

76.6

77.2

3.38-3.27 (1H, m)

6″

60.7

60.7

3.49 (1H, m); 3.70 (1H, dd; 2.4; 11.7)

3- OCH3

58.9


3.65 (3H, s)

a DMSO-d 6 , b 150 MHz, c 600 MHz, a* DMSO-d 6 , 125 MHz

9




Figure 3.24. Chemical structure of compound SXE17

* Compound SXE18

Compound SXE18 was obtained as a bright yellow color, ESI-MS spectrum showed pseudomolecular ion peaks m/z 488.9 [M - H] - and 491.0 [M + H] + , combined with 13 C-NMR spectrum showing 21 carbon units, consistent with the molecular formula C23H20O12 ( M = 490.1 ) .

The 1 H-NMR spectrum ( Table 3.17 ) of compound SXE18 shows proton signals similar to those of compound SXE16 except for the presence of an additional methoxy group at δ H 3.66 (3H, s). The presence of a low-field-shifted anomeric proton at δ H 5.35 (1H, d, J = 7.2 Hz, H-1″) confirms the presence of a β-sugar. In the 13 C-NMR spectrum ( Table 3.17 ) of compound SXE18 , the appearance of 21 carbon signals, of which 13 carbons belong to scutellarein derivatives, 4 carbon units at δ C 75.7-71.3 and one signal at δ C 99.4 indicate the presence of β -glucopyranose sugar, and two carbon signals at δ C 52.0 and δ C 60.4 belong to two methoxy groups. The appearance of two carbonyl carbons at δ C 182.4 and δ C 169.2 belongs to the carbonyl carbon of ring C and the remaining signal gives

prediction of the presence of a carbonyl group at position 6 of β -glucopyranose.

Combined with the HMBC spectrum, the interaction of the methoxy proton at δ H 3.75 (3H, s) with C-6 ( δ C 132.5) indicates that the methoxy group is attached to the C-6 position of the scutellarein derivative. On the other hand, the methoxy proton signal at δ H 3.66 (3H, s) interacts with C-6″ ( δ C 169.2), indicating that the ester bond is formed at the C-6″ position of the sugar ring. The interactions of the proton at δ H 7.95 (2H, d, J = 8.8 Hz, H-2′,6′) with C-2 ( δ C 164.4) indicate the binding site of the B ring to the C ring at the C-2 position. In particular, the interaction between the anomeric proton at δ H 5.35 (1H, d, J = 7.2 Hz, H-1″) with C-7 ( δ C 156.0) indicates a glycosidic bond between the aglycon and the sugar ring at position C-7 of the A ring. From the above data and references [ 179], it can be confirmed that compound SXE18 is hispidulin-7- O - β - glucuronopyranosid methyl ester ( Figure 3.25) .

Table 3.17. 1 H and 13 C-NMR spectral data of compound SXE18 and reference substance


C/H position

a,b

δ C

(ppm)

a*

δ C

(ppm)[179]

a,c

δ H

(ppm, Hz)

b*

δ H

(ppm, Hz) [ 179]

2

164.4

164.3



3

102.8

102.7

6.86 (1H, s)

6.95 (1H, s)

4

182.4

182.2



5

152.7

152.6



6

132.5

132.6



7

156.0

155.8



8

93.9

93.9

7.07 (1H, s)

7.06 (1H, s)

9

152.2

152.0



10

105.9

105.9



1'

121.1

121.0



2',6'

128.6

128.5

7.95 (2H, d; 8.8)

7.95 (2H, d; 8.8)

3',5'

116.1

116.0

6.95 (2H, d; 8.8)

6.95 (2H, d; 8.8)

4'

161.4

161.3



5-OH



13.0 (1H, s)


1''

99.4

99.5

5.35 (1H, d; 7.2)

5.32 (1H, d; 7.0)

2″

72.8

72.8


3.42-3.37 (3H, m)


3″

75.7

75.6


4″

71.3

71.2


5″

75.3

75.3

4.20 (1H, d; 9.6)

4.21 (1H, d; 9.0)

6″

169.2

169.0



6″-OCH 3

52.0

52.0

3.66 (3H, s)

3.67 (3H, s)

6- OCH3

60.4

59.7

3.75 (3H, s)

3.77 (3H, s)

a DMSO-d 6 , b 125 MHz, c 400 MHz, a* DMSO-d 6 , 100 MHz, b* DMSO-d 6 , 400 MHz


Figure 3.25. Chemical structure of compound SXE18

*SXE19 compound

Compound SXE19 was obtained as a bright yellow powder, ESI-MS spectrum showed pseudomolecular ion peaks m/z 446.8 [M + H] ⁺ and m/z 444.9 [M - H] ⁻ , combined with 13 C- NMR spectrum with 21 carbon signals consistent with the molecular formula C21H18O11 ( M = 446.1 ).

The NMR spectrum ( Table 3.18 ) of compound SXE19 showed similarities with compound SXE11 (apigenin) except for the presence of the sugar ring. The appearance of anomeric proton at δ H 5.09 (1H, d, J = 4.9 Hz, H-1″), comparing the NMR spectral data [116] allowed to predict the presence of a β sugar in the molecule, the proton signals in the remaining sugar ring were in the range of 3.30-3.68 ppm. The 13 C-NMR spectrum ( Table 3.18 ) showed the appearance of 19 carbon signals of which 12 carbon signals belong to the apigenin skeleton, 2 carbonyl carbon signals of which one signal belongs to the C- 4 position of the C ring, the remaining 4 carbon signals at δ C 73.4; 76.8; 72.4; 74.6 and the signal at δ C 100.1 and comparison with the 13 C NMR spectrum allows us to conclude the presence of β - glucuronopyranose sugar. Combined with the HMBC spectrum shows the interaction of the anomeric proton at δ H 5.09 (1H, d, J = 4.9 Hz, H-1″) with carbon C-7 ( δ C 163.4), which indicates a glycosidic bond at position 7 of the A ring. The interaction between the proton in the B ring at δ H 7.90 (2H, d, J = 7.7 Hz, H -2′, H-6′) with C-2 ( δ C 164.7) proves that the B ring and C ring are linked together through the C-2 position. From the above data combined with reference [116],

[210] could confirm the structure of compound SXE19 as apigenin-7- O - β - glucuronopyranoside ( Figure 3.26 ).

Table 3.18. 1 H and 13 C-NMR spectral data of compound SXE19 and reference substance


C/H position

a,b

δ C

(ppm)

a*

δ C

(ppm) [116]

a,c

δ H

(ppm, Hz)

2

164.7

163.6


3

103.4

103.2

6.81 (1H, s)

4

182.4

182.3


5

159.5

160.4


6

99.9

99.9

6.81 (1H, s)

7

163.4

163.2


8

95.1

95.1

6.41 (1H, s)

9

157.4

157.4


10

105.8

105.7


1'

121.2

120.9


2',6'

128.9

128.9

7.90 (2H, d; 7.7)

3',5'

116.5

116.4

6.91 (2H, d; 7.7)

4'

162.1

162.1


5-OH



12.97 (1H, brs)

1″

100.1

100.2

5.09 (1H, d; 4.9)

2″

73.4

73.5


3.30-3.25 (3H, m)

3″

76.8

77.1

4″

72.4

72.5

5″

74.6

74.1

3.68 (1H, d; 7.2)

6″

173.4

171.9


a DMSO-d 6 , b 125MHz, c 500 MHz, a* DMSO-d 6 , 150 MHz




Figure 3.26. Chemical structure of compound SXE19

* Compound SXE20

Compound SXE20 was obtained as a bright yellow color. From the resonance signals of protons and carbons on the 1 H and 13 C-NMR spectra ( Table 3.19 ), it was shown that compound SXE20 is also a derivative of quercetin glycoside. Comparing the number of carbon atoms of SXE20 with quercetin (15 C) ( SXE13) (Table 3.13) , combined with analysis of the signals

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