A new flavonoid from the bract of Zea mays L.

Article abstract of DOI:10.1016/j.cclet.2010.06.033

A new flavonoid was isolated from the bract of Zea mays L. The structure of the compound was identified as 4′,5,7-trihydroxy-3′,5′-dimethoxyflavone 7-O-[β- d-apiofuranosyl (1 → 2)]-β-d-glucopyranoside on the ground of chemical and spectroscopic methods.

Full text of DOI:10.1016/j.cclet.2010.06.033

Available online at www.sciencedirect.com
Chinese Chemical Letters 21 (2010) 1350–1351
www.elsevier.com/locate/cclet
A new flavonoid from the bract of Zea mays L.
Yan Wang a,b, Yin Yan Liu a, Xiao Hong Yang a, Di Chen a, Cheng Peng a,
Guang Shu Wang a,
*
a School of Pharmaceutical Sciences, Jilin University, Changchun 130021, China
b The Third Hospital, Jilin University, Changchun 130012, China
Received 6 April 2010
Abstract
A new flavonoid was isolated from the bract of Zea mays L. The structure of the compound was identified as 40,5,7-trihydroxy-
30,50-dimethoxyflavone 7-O-[b-D-apiofuranosyl (1 ! 2)]-b-D-glucopyranoside on the ground of chemical and spectroscopic
methods.
# 2010 Guang Shu Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Zea mays L.; Flavonoid; Bract
Zea mays (maize), a member of the Poaceae, is the most economically important crop in China and the third most
important crop plant in the world, and has many biological activities [1]. In our study, a novel flavonoid was isolated
for the first time from the bract of Zea mays L. The air-dried bract of Zea mays was extracted with 95% ethanol at room
temperature. The extract was subjected to Diaion AB-8 column chromatography eluted with ethanol–H2O, and the
eluate was further chromatographed on silica gel and Sephadex LH-20 columns repeatedly to yield the new
compound 1.
Compound 1, yellow amorphous powder, produced positive reactions to AlCl3 reagent and Molish reagent, had the
molecular formula C28H32O16 determined by HRESIMS ([M+H]+ 625.1760, calcd. 625.1763). Acid hydrolysis gave
two kinds of monosaccharides, one of which was identified as D-glucose by paper chromatography comparison with
authentic D-glucose. The IR spectrum of 1 indicated the presence of hydroxyl (3420 cmꢀ1), a carbonyl (1650 cmꢀ1
)
and an aromatic (1609 cmꢀ1) groups. UV maxima occurred at 349 nm (band I) and 269 nm (band II), characteristic of
a flavonoid system. All the above data suggested that 1 was a flavonoid glycoside. The 1H NMR spectrum (400 MHz,
DMSO-d6) showed two hydroxyl active proton signals at d 12.96 (brs, 1H, 5-OH), 9.38 (brs, 1H, 40-OH) in the lower
field; five aromatic proton signals at d 7.36 (brs, 2H, H-20,60), 7.08 (s, 1H, H-3), 6.91 (d, 1H, J = 2.0 Hz, H-8), 6.44 (d,
1H, J = 2.0 Hz, H-6), two methoxy proton signals at d 3.88 (s, 6H, 30,50-OCH3). From the above information, the
aglycone was identified as tricin, 40,5,7-trihydroxy-30,50-dimethoxyflavone, on further comparing corresponding 13C
NMR data with the reported [2]. The coupling constant of the anomeric proton of glucose at d 5.16 (d, 1H, J = 6.0 Hz)
indicated that glucose moiety was in b-configuration. Besides the signals attributed to glucose moiety, there were four
* Corresponding author.
E-mail address: wgs@jlu.edu.cn (G.S. Wang).
1001-8417/$ – see front matter # 2010 Guang Shu Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.06.033

Y. Wang et al. / Chinese Chemical Letters 21 (2010) 1350–1351
1351
Table 1
1H NMR (400 MHz), 13C NMR (100 MHz), HMQC and HMBC data of compound 1 (DMSO-d6, d).
No.
dC
dH
HMBC (H ! C)
No. dC
dH
HMBC (H ! C)
2
164.1
7-O-sugar
3
103.8 7.08 (s, 1H)
182.0, 164.1, 120.2, 105.4 glc
4
182.0
161.1
100
200
98.3 5.16 (d, 1H, J = 6.0 Hz)
77.2 3.47 (m, 1H)
162.7, 76.1
108.7, 98.3
5
6
99.4 6.44 (d, 1H, J = 2.0 Hz) 161.1, 105.4, 95.2
300
400
500
600
api
76.1 3.75 (t, 1H, J = 4.2 Hz)
69.9 3.17 (m, 1H)
7
162.7
8
95.2 6.91 (d, 1H, J = 2.0 Hz) 105.4, 99.4
75.9 3.51 (m, 1H)
9
156.9
105.4
120.2
60.6 3.73, 3.44 (m, each 1H)
10
10
20,60
1& 108.7 5.35 (s, 1H)
2& 76.8 3.56 (m, 1H,)
74.0, 79.2
104.5 7.36 (s, 2H)
164.1, 148.2, 140.1,
120.2, 104.5
30,50
40
148.2
140.1
3& 79.2
4& 74.0 3.92, 3.66 (d, each 1H, J = 9.2 Hz) 79.2
5& 64.2 3.23 (m, 2H)
30,50-OCH3 56.4 3.88 (s, 6H)
148.2
All assignments based on the extensive 1D and 2D NMR spectra (HMQC, HMBC, 1H–1H COSY).
[(Fig._1)TD$FIG]
Fig. 1. The key HMBC correlation of compound 1 (arrows point from proton to carbon).
signals at d 76.8, 79.2, 74.0, 64.2 in the region between d 60.5 and 70.9, and one signal at d 108.7 in the anomeric region
between d 95.1 and 108.8, which were attributed to b-D-apiose by comparing with the reported [3]. The complete
assignment of the signals of compound 1 was based on 2D NMR of 1H–1H COSY, HMQC and HMBC. The down field
about 4 ppm of the signal of C-200 of glucose (d 77.2) showed that apiose was linked to C-200 of glucose, which was
further confirmed by the HMBC correlation of 200-H (dH 3.47) to C-1 (dC 108.7). The HMBC correlation of 100-H (dH
5.16) to C-7 (dC 162.7) showed that glucose was linked to C-7 of alycone, which was further confirmed by free active
hydroxyl protons of C-5 (dH 12.96) and C-40 (dH 9.38) and the HMBC correlation of 5-OH (dH 12.96) to C-6 (dC 99.4).
For all the remaining assignments of 1H NMR and 13C NMR see Table 1, and for all the remains of HMBC correlation
see Fig. 1. Therefore, the structure of compound 1 was elucidated as 40,5,7-trihydroxy-30,50-dimethoxyflavone 7-O-[b-
D-apifuranosyl (1 ! 2)]-b-D-glucopyranoside.
References
[1] The Health Department and National Chinese Medicine Management Office. Zhonghua Bencao 8. Shanghai Scientific and Technical Publishers,
Shanghai. (1999) pp. 436.
[2] Q. He, E.Y. Zhu, Z.T. Wang, et al. J. Chin. Pharm. Sci. 13 (3) (2004) 212.
[3] X.K. Zheng, J. Li, W.S. Feng, et al. Acta Pharmaceutica Sinica 38 (4) (2003) 268.