R. Li, et al.
Fitoterapia 137 (2019) 104248
Fig. 3. Derivation process of sugar by PMP derivatization.
there are a little bit different shifts between them at combing of sugars
Tables 1 and 2). Moreover, the signal at δ 6.69 (1H, t, J = 7.2 Hz, H-
‴″) indicated the presence of the (E)–substituted double bond.
Therefore, the monoterpenoic acid moiety of 1 were determined to be
775.2449) in the UPLC-ESI-Q-TOF-MS/MS, implying 16 degrees of
1
13
(
3
H
unsaturation. The H and C NMR data of 3 was resemble of 1, except
for the lacking of a rhamnose. Thus, the structure of compound 3 was
assigned as kaempferol-3-O-β-D-glucosyl-7-O-{2-O-[(2E)-2,6-dimethyl-
6-hydroxy −2,7-octadienoyl]}-β-D-glucoside.
1
(
2E)-2,6-dimethyl-6-hydroxy-2,7-octadienoic acid. In the H-NMR
spectrum, the chemical shifts indicated β-configuration [δ 5.44 (1H, d,
H
Compounds 4–13 were identified by compared with literature data,
and the ten known compounds were identified as kaempferol-3-O-β-D-
sophoroside-7-O-α-L-rhamnoside (4) [14,15], kaempferol-3-O-[(2E)-
2,6-dimethyl-6-hydroxy-2,7-octadienoyl(1 → 6)]-β-D-glucoside(1 → 2)-
β-D-glucoside-7-O-α-L-rhamnoside (Hippophin K; 5) [6], kaempferol-3-
O-β-D-sophoroside−7-O-{[(2E)-2,6-dimethyl-6-hydroxy-2,7-octadie-
noyl(1 → 2)]}-α-L-rhamnosider(6) [6], kaempferol−3-O-β-D-sophoro-
side-7-O-{[(2E)-2,6-dimethyl-6-hydroxy-2,7-octadienoyl(1 → 3)]}-α-L-
rhamnoside (7) [6], kaempferol-3-O-(6-O-3,4,5-trimethoxycinnamoyl)-
β-D-glucoside(1 → 2)-β-D-glucoside-7-O-α-L-rhamnoside (Hippophin M;
8) [8], kaempferol-3-O-(3-O-trans-sinapoyl)-β-D-glucoside(1 → 2)-β-D-
glucoside-7-O-α-L-rhamnoside (9) [8], kaempferol-3-O-(6-O-E-fer-
uloyl)-β-D-glucosyl(1 → 2)-β-D-glucoside-7-O-[(2E)-2,6-dimethyl-6-hy-
droxy-2,7-octadienoyl(1 → 2)]-α-L-rhamnoside (Hippophin F; 10) [7],
kaempferol-3-O-(6-O-E-sinapoyl)-β-D-glucosyl(1 → 2)-β-D-gluco-
side−7-O-[(2E)-2,6-dimethyl-6-hydroxy-2,7-octadienoyl (1 → 2)]-α-L-
rhamnoside (Hippophin D; 11) [7], kaempferol-3-O-(6-O-E-feruloyl)-β-
D-glucosyl(1 → 2)-β-D-glucoside-7-O-[(2E)-2,6-dimethyl−6-hydroxy-
2,7-octadienoyl(1 → 3)]-α-L-rhamnoside (Hippophin E; 12) [7] and
kaempferol-3-O-(6-O-E-sinapoyl)-β-D-glucosyl(1 → 2)-β-D-glucoside-7-
O-[(2E)-2,6-dimethyl-6-hydroxy-2,7-octadienoyl(1 → 3)]-α-L-rhamno-
J = 8.0 Hz, H-1‴′), 5.36 (1H, d, J = 7.2 Hz, H-1″)] for the two gluco-
pyranosyl group [6,13]. On the acid hydrolysis of 1 with hydrochloric
acid, β-D-glucose and α-L-rhamnose were detected by HPLC in com-
parison with the authentic samples (See Experimental). Thus, com-
pound 1 was characterized as kaempferol-3-O-β-D-rutinosyl-7-O-{2-O-
[
(2E)-2,6-dimethyl-6-hydroxy-2,7-octadienoyl]}-β-D-glucoside.
Hippophin O (2) was obtained as yellow amorphous powder. Its
54
molecular formula was confirmed as C43H O22 on the basis of its ne-
−
−
gative-ion peak [M - H] at m/z 951.3160 (calcd. for C44
55 23
H O ,
9
51.3134) in the UPLC-ESI-Q-TOF-MS/MS, implying 17 degrees of
1
unsaturation. The H NMR data exhibited signals at low field for a
isorhamnetin skeleton, which was characterized by two meta-coupled
aromatic protons [δ
H
6.41 (1H, d, J = 2.0 Hz) and 6.81 (1H, d,
6.98 (1H, d, J = 8.4 Hz),
.62 (1H, dd, J = 8.4, 1.6 Hz) and 7.92 (1H, d, J = 2 Hz)] and methoxy
J = 2.0 Hz)], ABX-type aromatic protons [δ
H
7
1
13
H
protons [δ 3.90 (3H, s)]. The H NMR and C NMR spectral data of 2
were resembled to those of 1, except for the isorhamnetin skeleton.
Three sugars were identified by HPLC analysis after hydrolysis (see
Experimental). The HMBC spectrum displayed glucose II [δ
d, J = 8.0 Hz, H-1‴′)] was connected to C-7 of isorhamnetin (δ
C-7), monoterpenyl moiety (δ 166.8, C-1‴‴) was linked to C-2″″ of
glucose II [δ 4.92 (1H, t, J = 9.2 Hz, H-2‴‴)], and rhamnose (δ
01.3, C-1″″) was located at C-6″ of glucose I δ 3.41 (1H, m, H-6″)
Fig. 2). However, 2D-NMR spectra failed to display the long-rang
H
5.48 (1H,
C
162.7,
1
13
C
side (Hippophin C; 13) [7]. The H NMR and C NMR data of these
compounds were given at supplementary data.
H
C
1
H
Though we have discovered a series of flavonoids acylated with one
monoterpenic acid or phenylpropionic acid in H. rhamnoides, 1–3 were
(
2
correlation of the glucose I and C-3 of isorhamnetin. Comparing the
NMR data of 2 with 1, there was no obviously different shift between
the H-1″ of glucose I and C-3 of isorhamnetin (Fig. 4) and 1D-NMR
spectra of H-1″ of glucose I existed glycosylation shift, which suggested
that the location of the glucose I was at C-3 of isorhamnetin. Thus, the
structure of compound 2 was assigned as isorhamnetin-3-O-β-D-ruti-
nosyl-7-O-{2-O-[(2E))-2,6-dimethyl-6-hydroxy-2,7-octadienoyl]}-β-D-
glucoside.
first found as different sugar-linked configuration and their MS spectra
were also different. The negative ion peak at m/z 737 or 767 ([M–H-
−
2
184] ) in MS spectra of 1–2 resulted from a loss of monoterpenyl
moiety, indicating the presence of McLafferty Rearrangement reaction.
−
Fragments at m/z 593 or 623 ([M–H-184-144] ) and m/z 285 or 315
−
2
([M–H–184–144 -308] ) indicated the loss of sugars. While, MS of the
other compounds were similar to 6, which observed fragmentation
−
−
−
[M–H -166] , [M–H–166-146] and [M–H-166–146-324] . (Fig. 5).
Hippophin P (3) was obtained as yellow amorphous powder. Its
44
molecular formula was confirmed as C37H O18 on the basis of its ne-
−
−
43 18
gative-ion peak [M - H] at m/z 775.2446 (calcd. For C37H O ,
Fig. 4. Key HMBC and 1He H COSY correlations for compounds 1–3.
1
5