A flavone glycoside from Andrographis alata

Article abstract of DOI:10.1016/S0031-9422(98)00342-2

A new flavone glycoside, echioidinin 5-glucoside along with its known aglycone, echioidinin have been isolated from the whole plant of Andrographis alata. The structure of the new compound was established as 5,2'-dihydroxy- 7-methoxyflavone 5-O-β-D-glucop

Full text of DOI:10.1016/S0031-9422(98)00342-2

Phytochemistry Vol. 49, No. 6, pp. 1811±1813, 1998
# 1998 Published by Elsevier Science Ltd. All rights reserved
Printed in Great Britain
0031-9422/98/$ - see front matter
PII: S0031-9422(98)00342-2
A FLAVONE GLYCOSIDE FROM ANDROGRAPHIS ALATA
A. G. DAMU, B. JAYAPRAKASAM, K. V. RAO and D. GUNASEKAR*
Natural Products Division, Department of Chemistry, Sri Venkateswara University, Tirupati-517 502,
India
(Received 11 March 1998)
Key Word IndexÐAndrographis alata; Acanthaceae; whole plant; ¯avone glycoside; echioidi-
nin 5-O-b-D-glucopyranoside.
AbstractÐA new ¯avone glycoside, echioidinin 5-glucoside along with its known aglycone, echioidinin
have been isolated from the whole plant of Andrographis alata. The structure of the new compound was
established as 5,2'-dihydroxy-7-methoxy¯avone 5-O-b-D-glucopyranoside on the basis of spectral and
chemical studies. # 1998 Published by Elsevier Science Ltd. All rights reserved
INTRODUCTION
tion band at 3200 and a carbonyl absorption band
1
at 1652 cm
.
Andrographis alata Nees (Acanthaceae) is an erect
herb which occurs widely in South India [1]. A
number of unusual ¯avones and ¯avone glycosides
have been reported from Andrographis species
[2±10] but this plant has not been investigated so
far. Our phytochemical investigation of the whole
plant of Andrographis alata has resulted in the
isolation of a new ¯avone glycoside, echioidinin
5-glucoside (2) together with its known aglycone,
echioidinin (1).
The 1H NMR spectrum of 2 exhibited a meth-
oxyl singlet at d 3.89 and a one-proton singlet at d
7.06 characteristic of C-3 proton of a 2'-oxygenated
¯avone [13]. Two meta coupled doublets at d 6.91
and 6.98 were assigned to C-6 and C-8 protons, re-
spectively. A broad singlet at d 10.70 exchangeable
with D2O was assigned to a nonchelated hydroxyl
group at C-2' since the signal due to H-3 in the
penta-acetate of 2 appeared at a signi®cantly higher
®eld (d 6.14) than in 2 (d 7.06) [13]. It also dis-
played the characteristic signal pattern of a 2'-oxy-
genated B-ring [9] at d 7.94 (dd, 1H, J = 2, 8 Hz),
7.38 (dt, 1H, J = 2, 8 Hz) and 7.02±7.04 (m, 2H),
which were assigned to the C-6', C-4' and C-3', 5'
protons, respectively. The spectrum also showed the
presence of a glucose moiety [d 4.78 (d, J = 7 Hz,
H-1 ) and 3.35-3.85 (m, 5H)].
RESULTS AND DISCUSSION
The defatted methanolic extract of the whole
plant of A. alata on puri®cation over a silica gel
column, a€orded 1 and 2. Compound 1 was ident-
i®ed as echioidinin by comparison of its mp and
spectral data with published values [2, 11].
The positive FAB mass spectrum of 2 showed
[M + H]+ peak at m/z 447 corresponding to the
molecular formula C22H22O10 and a prominent
fragment at m/z 285 [M + H-162]+ indicating the
loss of an hexose moiety. The UV absorption
maxima of 2 at 257, 305 and 330 nm is typical of a
¯avone derivative [12]. It responded positively to
the Molisch test indicating it to be a ¯avone glyco-
side. The addition of AlCl3 and NaOAc caused no
shift in its UV spectrum indicating the absence of
free hydroxyl groups at C-5 and C-7, respectively.
The IR spectrum of 2 showed an hydroxyl absorp-
Acid hydrolysis of 2 with 2N HCl a€orded glu-
cose and an aglycone identi®ed as echioidinin
(1) [2, 11]. The presence of a chelated hydroxyl sig-
nal at d 12.87 in the aglycone (1) and not in the gly-
*Author to whom correspondence should be sent.
1811

1812
Short Report
n-hexane and the residue obtained on CC over
silica gel using CHCl3±EtOAc step gradient
Table 1. 13C NMR spectral data of
compounds 1 and 2 (75.4 MHz, ppm,
DMSO-d6)
a€orded 1 (150 mg) and 2 (260 mg).
C
1
2
Echiodinin (1)
Green±yellow needles (MeOH); mp 264±2658;
2
3
4
5
6
7
8
161.4
109.1
182.0
161.0
97.8
158.5
112.0
177.1
158.0
103.3
163.5
96.4
MeOH
UV
+NaOMe: 265, 390; +NaOAc: 265, 335; +AlCl3:
l
max
nm (log E): 265 (4.40), 335 (4.19);
250, 274, 285 sh, 315 sh, 355; +AlCl3/HCl: 235,
KBr
max
cm 1: 3400 (OH), 2980, 1654
165.1
92.4
265, 315, 355; IR n
(C.O), 1615, 1520, 1456, 1360, 1H NMR (DMSO-
d6): d 12.87 (OH-5), 10.86 (OH-2'), 7.90 (1H, dd,
J = 2,8 Hz, H-6'), 7.40 (1H, dt, J = 2,8 Hz, H-4'),
7.11 (1H, s, H-3), 6.99-7.06 (2H, m, H-3', 5'), 6.73)
(1H, d, J = 2.5 Hz, H-8). 6.35 (1H, d, J = 2.5 Hz,
H-6), 3.90 (3H, s, OMe-7), 13C NMR: Table 1;
ELMS m/z (rel. int): 284 [M]+ (100), 267 [M±OH]+
(1) 255 [M±CHO]+ (5), 254 [M±CO]+ (2), 166
[A1]+ (4), 118 [B1]+ (1).
9
10
1'
2'
3'
4'
5'
6'
1
157.3
104.6
117.0
156.7
116.9
132.8
119.3
128.4
158.7
109.1
117.0
156.6
116.9
132.4
119.2
128.2
104.1
73.5
2
3
4
77.5
69.8
5
75.6
60.8
55.9
6
7-OMe
Echioidinin 5-O-b-D-glucopyranoside (2)
55.9
Pale yellow needles (MeOH), mp 245±2468; FAB-
MS (positive mode) m/z (rel. int): 447 [M + H]+
(5), 285 [M + H-glucosyl]+ (23); UV l
nm
MeOH
max
coside (2) indicated that the glucose moiety in 2
must be attached to the C-5 hydroxyl group. The
5-O-glycosylation in 2 was further con®rmed by a
comparison of 13C NMR data of 2 with 1 (Table 1)
which showed up®eld shifts of 3.0 and 4.9 ppm for
the C-5 and C-4 resonances, and down®eld shifts of
5.5 and 4.5 ppm for the C-6 and C-10 resonances,
respectively [14]. The coupling constant (J = 7 Hz)
of the anomeric proton signal at d 4.78 indicated
the b-con®guration of the glucopyranoside. Thus, 2
was characterized as echioidinin 5-O-b-D-glucopyra-
noside.
(log E) 257 (4.38), 305 (4.33) and 330 (4.25);
+NaOMe: 257 sh, 300 sh, 400 + NaOAc: 257, 305,
342 sh; +AlCl3: 257, 315, 348 sh; +AlCl3/HCl:
KBr
257, 288 sh, 335; IR n
cm 1: 3200 (OH), 2950,
max
1652 (C.O), 1618, 1560; 1H NMR (DMSO-d6): d
10.70 (OH-2'), 7.94 (1H, dd, J = 2, 8 Hz, H-6'),
7.38 (1H, dt, J = 2, 8 Hz, H-4'), 7.02±7.04 (2H, m,
H-3', 5'), 7.06 (1H, s, H-3), 6.98 (1H, d, J = 2.5 Hz,
H-8), 6.92 (1H, d, J = 2.5 Hz, H-6), 4.78 (1H, d,
J = 7 Hz, H-1 ), 3.91 (3H, s, OMe-7), 3.35±3.85
(5H, m, sugar protons), 13C NMR: Table 1.
Acid hydrolysis of 2
A MeOH soln. of 2 (20 mg) in 2N HCl (5 ml)
heated at 1008 for 1 h gave glucose and (1) (12 mg)
identi®ed by mp, UV, IR, 1H and 13C NMR
analysis.
EXPERIMENTAL
General
Mps: uncorr. UV and IR: MeOH and KBr discs,
respectively. 1H and 13C NMR: 300.13 and
75.43 MHz, respectively in DMSO-d6 and CDCl3
with TMS as int. standard. EIMS at 70 eV (direct
probe). FABMS was registered in positive ion mode
using a glycerol matrix. CC: Silica gel ®ner than
200 mesh (0.08 mm).
Acetylation of 2
A mixture of 2 (10 mg), Ac2O (2 ml) and C5H5 N
(1 ml) was kept at room temp. for 48 h and poured
into crushed ice to yield the penta-acetate of 2 as
colourless crystals (12 mg) from MeOH, mp 1208
KBr
IR n
cm 1: 1760 (C.O of OAc), 1654 (C.O),
max
1619, 1465, 1433, 1369, 1345, 1196; 1H NMR
(CDCl3) d: 7.47 (2H, m, H-4', 6'), 7.12 (1H, m,
H-3'), 6.96 (1H, m, H-5'), 6.67 (1H, d, J = 2.5 Hz,
H-8), 6.63 (1H, d, J = 2.5 Hz, H-6), 6.14 (1H, s,
H-3), 5.08 (1H, d, J = 7 Hz, H-1 ), 5.10-5.19 (4H,
m, H-2 , 3 , 4 , 5 ), 4.19±4.27 (2H, m, CH2-6 ), 3.89
(3H, s, OMe), 2.42 (3H, s, OAc-2'), 1.91±2.08 (12H,
m, 4 ÂOAc).
Plant material
The whole plant of Andrographis alata Nees was
collected from the Talakona hills, Andhra Pradesh,
India, in January 1995. A voucher specimen has
been deposited in the Herbarium of the Department
of Botany, Sri Venkateswara University, Tirupati.
Extraction and isolation
Dried and powdered whole plant (2.5 kg) were
successively extracted with n-hexane, Me2CO and AcknowledgementsÐThe authors thank Dr K.
MeOH. The MeOH extract was defatted with Prabhavathi, Department of Chemistry, Hong

Short Report
1813
Kong University, Hong Kong for providing the
spectral data and Dr K. Madhava Chetty,
6. Govindachari, T. R., Pai, B. R., Srinivasan, M.
and Kalyanaraman, P. S., Indian Journal of
Chemistry, 1969, 7, 306.
Department
of Botany,
Sri
Venkateswara
University, Tirupati for collection and identi®cation
of plant material. B. J. is grateful to CSIR, New
Delhi for ®nancial support.
7. Jalal, M. F., Overton, K. H. and Rycroft, D. S.,
Phytochemistry, 1979, 18, 149.
8. Gupta, K. K., Taneja, S. C., Dhar, K. L. and
Atal, C. K., Phytochemistry, 1983, 22, 314.
9. Kuroyanagi, M., Sato, M., Ueno, A. and
Nishi, K., Chemical and Pharmaceutical
Bulletin, 1987, 35, 4429.
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