TRITERPENOIDS FROM MANGIFERA INDICA

Article abstract of DOI:10.1016/S0031-9422(00)97767-7

A new pentacyclic triterpenoid, hopane-1β,3β,22-triol, was isolated from the neutral fraction of the n-hexane extract of the stem bark of Mangifera indica.From the acidic fraction of the same extract four new tetracyclic triterpenoids, 3α,22(R or S)-dihydroxycycloart-24E-en-26-oic acid, 3β,22(R or S)-dihydroxycycloart-24E-en-26-oic acid, 3β,23(R or S)-dihydroxycycloart-24E-en-26-oic acid and 3α,27-dihydroxycycloart-24E-en-26-oic acid were isolated.The structures were elucidated by spectroscopic and chemical methods. - Keywords: Mangifera indica; Anacardiaceae; triterpenoids.

Full text of DOI:10.1016/S0031-9422(00)97767-7

Vol. 28, No. p p . 1471-1477, 1989.
P r in ted in Gr ea t Br ita in .
1989
Press
TRITERPENOIDS FROM
V.
K.
K. H AR I S C H AN D R A
P
R AS AD and J. D.
530003, India;
Organic Chemistry Laboratories, School of Chemistry, Andhra University,
University of Glasgow, Glasgow G12
of Chemistry,
Scotland, U.K.
(Received 14 July 1988)
Key Word
indica;
triterpenoids.
Abstract-A new pentacyclic triterpenoid,
hexane extract of the stem bark of
was isolated from the neutral fraction of the
indica. From the acidic fraction of the same extract four new tetracyclic
triterpenoids,
or S)-dihydroxycycloart-24E-en-26-oic acid,
or
acid,
or S)-dihydroxycycloart-24E-en-26-oic acid and
acid were
isolated. The structures were elucidated by spectroscopic and chemical methods.
INTRODUCTION
pyridine at room temperature has not been observed
previously in cycloartanes.
has
In our previous papers
triterpenoids from various parts of the Banganpalli var-
iety of indica L. In continuation of our studies
we have reported the
not been isolated previously from any part of
indica.
Compound B, mp
analysed for
Its
3) and eight methyls between 0.76 and 1.09. It formed a
monoacetate mp 267-268” 1.98 and 4.42 (H-3)]
whose IR spectrum still exhibited the presence of
cm which presumably is tertiary as it resisted
NMR spectrum displayed a multiplet at 3.18
on the triterpenoid constituents from different varieties of
M. indica, we have now investigated the stem-bark of the
Neelum variety. From this material five new and several
known triterpenoids have been isolated.
acetylation. The above data indicated that compound B
was a saturated dihydroxy pentacyclic triterpenoid.
R E SULTS AND DISCUSSION
Dehydration of
with thionyl chloride in pyridine
The neutral fraction of the n-hexane extract of M.
indica afforded several known compounds, namely
a-amyrin, sitosterol,
cycloart-24-en-26-al, the C-24 epimers of
yielded a compound, mp
identified as
which was readily
by direct com-
acetate
loartenol,
parison with the authentic sample (mmp, co-TLC and
NMR). Therefore, compound B must be one of the
20 epimers of
mmp of compound B and authentic
diol was depressed. The physical and spectral character-
istics of compound B and its acetate agree closely with
(2)
5, 63. The
the C-24 epimers of
the C-24 epimers of
and a new pentacyclic triterpenoid (3).
those of
(2a)
(2) and its acetate
The acidic fraction of the same extract on column chro-
matography gave four new tetracyclic triterpenoids (4,
6) besides mangiferonic acid, isomangiferolic acid,
mangiferolic acid and hydroxymangiferolic acid.
respectively. Therefore, compound B is
(2). The
of 2 was as-
(Table 1).
signed by comparison with taraxasterol(7)
has not been previously
reported from any part of M. indica and this is the second
report of its natural occurrence.
C o m p o u n d A , m p
at m/z 4443. Its
analysed for
displayed no
olefinic protons and showed signals for a secondary
Compound C was crystallized from
as
hydroxyl
and a cyclopropane methylene
= 4 Hz)]. The downfield shift of the two methyls (6 1.23)
3-H)], seven methyls (6
flakes mp 253-255” and analysed for
Its IR spectrum indicated the presence of
and 0.33
hydroxyl (3550
Its
NMR spectrum could not
indicated a substituted
ylation, compound A gave two products, the more polar
compound was the diol monoacetate (la) and the less
system. On
be secured due to its insolubility in common NMR
solvents. Acetylation of compound C afforded a trio1
diacetate
an acetate carbonyl (1725
(3600 Its NMR spectrum lacked olefinic pro-
tons and displayed two secondary acetates and
4.65 (both dd, and 12 Hz)] and eight methyls
mp 262-264” whose IR spectrum showed
polar compound, mp
possessing a
was a monoacetate (lb)
and a hydroxyl
terminal methylene
890
64.78 (s,
The above data suggested
the structure of compound A as
5
Compound lb is the dehydration product of la.
(60.71-1.18). The downfield shift of the two methyls
(6 1.18 and 1.16) suggested an hydroxyisopropyl group in
the molecule. The above evidence indicated that com-
pound C was a trihydroxy pentacyclic triterpenoid with a
or lupane skeleton.
Dehydration of the C-25 hydroxyl with acetic
*Au t h or t o whom correspondence should be addressed.
1471

V.
et al.
1472
OH
la
l b
9
O
H
displayed signals for a cyclopropane methylene (60.32
The mass spectrum of compound C showed no molecu-
lar ion but showed the ions at m/z 442 424 [M
and 0.50,
Hz), five methyls
a
vinylic methyl
two secondary hydroxyls (3.41
and 3.75 m) and an
proton (6.90 t). The broad
207,189 and 149 are typical of 22-hydroxyhopanes
or
singlet at 3.41 is characteristic of a proton geminal to a
hydroxyl in cycloartanes. On treatment with
diazomethane, compound D formed a methyl ester
20-hydroxylupanes and suggested that the other two
hydroxyls were in rings AB. Ions at m/z 171 and 157
restricted the placement of these two hydroxyls to ring A.
A literature survey of various trihydroxyhopane and
lupane derivatives revealed that the physical and spectral
data of compound C acetate were in very close agreement
mp
whose
spectrum showed
at
3.45 and a four proton broad singlet at 3.78 assignable
to the geminal proton of a secondary hydroxyl and three
protons of a carbomethoxyl group. On acetylation with
acetic anhydrideepyridine at room temperature, com-
with those of
compound C was
( 3a )
(3).
Thus,
pound D formed a diacetate
mp
the
has been previously reported
NMR spectrum of which showed two acetate methyls
at 6 2.02 and 2.06 and the corresponding geminal protons
as a saponification product of
diol ( 3b) isolated from the lichen Pseudoparmelia
This is the first report of its natural occurrence and
it is also the first new pentacyclic triterpenoid from
at 4.68
and 5.02. The above data indicated that
derivative
compound D was a new
having two secondary hydroxyls and an x,/i-unsaturated
carboxyl group.
The mass spectral fragmentation of compound D
showed a molecular ion at m/z 472 and the corresponding
Compound D, mp
spectrum exhibited the presence of hydroxyls
(3500 cm-‘) and a&unsaturated carboxyl group
and 1640 cm Its ‘H NMR spectrum
analysed for
Its
ions due to loss of water at
454 and 436. Ions at m/z

Triterpcnoids from
1473
2
R
=
AC
3
=
=
AC
3b
=
H,
= AC
332, 315 and 175 were the characteristic fragments of a
Table 1.
of compounds 2 and
signals
triterpenoid
with one hydroxyl in
7
rings AB and the other hydroxyl in a side chain bearing
an @-unsaturated carboxyl group. An ion at m/z 385,
due to loss of carbons 2, 3 and 4, suggested that the
hydroxyl of rings AB should be placed in ring A, probably
at C-3. The hydroxyl present in the side chain must be
either at C-22 or C-23. From the multiplicity of the
TMS as int. stan-
dard)
C
2
7
1
38.8
27.4
79.0
38.3
55.1
18.4
34.4
41.2
49.5
36.9
21.3
26.5”
38.6
42.0
26.5
38.7
27.3
78.9
38.7
55.3
18.2
34.0
40.8
50.4
37.0
21.3
25.5’
38.7
41.9
26.6
olefinic proton (triplet) in the
compound D and its derivatives, the hydroxyl was lo-
cated at C-22. It is well known that the proton
spectrum of
2
3
4
5
6
7
8
9
cis to the carboxylic group is significantly more
shielded than the
shift of the
Therefore, the downfield
proton in the spectra of
compound D and its derivatives clearly suggested the
configuration of the double bond. Thus, all the above
data suggested that compound D was
dihydroxycycloart-24E-en-26-oic acid (4).
or
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
The structure of compound D was further supported
by its
spectrum. The
chemical shifts of
compound D were compared with those of
acid (8) and this is also the first report of the
data of the latter. The
assignment of the
carbon resonances of the nucleus of compound D were in
close agreement with those of compound 8 confirming the
hydroxyl at C-3. The chemical shift of the C-21
35.6
47.9
37.8
75.3
21.4”
34.4
48.5
38.2
154.4
25.4”
methyl was observed at 12.3 since it is shielded by the
22
group. The signal of C-27 methyl (6 11.9)
clearly supported the E-configuration of the double bond
since it is shielded by the steric interaction with C-23
methylene.
27.9
15.2
15.8
16.1
14.6
26.1
19.3
28.0
14.7
15.4
16.1
14.7
28.5
17.4
27.4
Mixture I, mp
analysed for
and
showed a single spot on TLC in various solvent systems.
Its IR absorption spectrum displayed bands for hydroxyl
(3500
unsaturated
carboxyl
and
1640
Methylation of
mixture I with diazomethancproved unsuccessful due to
107.0
formation of diazomethane
trum of mixture I (in
The
NMR spec-
showed signals
b earin g th e
same superscript may be
interchanged.
at 60.30 and 0.50 for cyclopropane methylene, methyls
between 0.78 and 0.98, two signals for vinylic methyls at

V.
et al
1474
74.0 and 67.4 as doublets. The chemical shifts of C-l
1.82 and 1.85, two olefinic protons at 6.57 and 6.90 as a
doublet and a triplet, respectively. The region of the
chemical shifts of protons geminal to hydroxyls was
(6
C-5
C-29 (6 26.4) and C-30 14.5) indi-
in both
cated that the hydroxyl at C-3 was equatorial
the compounds. Doubling of carbon resonances in the
side chain suggested that these two compounds differ
only in the position or configuration of the secondary
hydroxyl. The multiplicities of the olefinic proton at
buried under
and water peaks.
The mass spectrum of mixture I showed the molecular
ion at m/z 472 and corresponding ions due to loss of water
at
454 and 436 indicating the presence of two
6.90 as a triplet and 6.57 as a doublet in the
mixture I clearly indicated the presence of a hydroxyl at
C-22 in one compound and at C-23 in the other. Further,
NMR of
hydroxyls. Ions at m/z 332, 315 and 175 were observed
which suggested that the components of the mixture I
bears one hydroxyl in rings AB and the other hydroxyl in
the side chain which possesses an a&‘-unsaturated
boxy1 group.
the downfield shift of the
protons confirmed the
E-configuration of the double bond in both the com-
pounds. Thus, the structures of the two new compounds
Thus, from the above evidence, it was concluded that
of mixture 1 were established as
acid
or
mixture I consists of two
dihydroxycycloartane
and
acid (5b).
or
derivatives both possessing a cycloart-24-en-26-oic acid
system. Attempts to separate the mixture into its con-
stituents were not successful.
Compound E, mp 2055207 analysed for
and showed the presence of hydroxyl
The
NMR spectrum (Table 2) of mixture I further
and
carboxyl
1695 and
confirmed the presence of two compounds and gave
1645 cm-‘) in its
spectrum. Its
NMR spectrum
much evidence regarding their structures. Comparison of
showed signals for a cyclopropane methylene (6 0.33 and
0.53, = 4.2 Hz) and five methyls between 0.86 and
the
signals of mixture I with those of isomangiferolic
revealed that both the
acid (8) and cycloartenol (9)
0.99 besides a triplet at 7.0 for an olefinic proton. It
further displayed a broad singlet at 3.48 assignable to
compounds of the mixture had the same nucleus and
variation was observed only in the nature of the side
chain. It showed three hydroxyl bearing carbons at 6 79.4,
the proton geminal to
hydroxyl and a
Table 2.
NMR signals of compound D
mixture
compound E
8 and 9 (TMS
as int. standard with solvent system indicated in parentheses)
C
9
1
27.3
28.3
76.8
39.4
40.9
20.9
29.6
47.9
19.6
26.3
25.6
32.7
45.5
48.3
35.5
26.0
49.1
19.2”
29.9
42.2
12.3
72.8
27.
33.8
31.2
79.4
42.0
47.3
22.4
29.5
49.0
21.2
27.8
27.4
34.7
46.4
49.8
35.2
27.4
51.5, 51.6
20.0”
29.8
44.4, 37.6
12.8. 20.0
74.0, 37.6
28.2, 67.4
26.8
28.0
75.5
38.8
40.
20.3
27.3
48.1
18.9
25.5
25.8
32.9
44.5
47.3
34.7
24.9
51.3
27.4
28.5
77.1
39.5
41.1
21.0
28.1
32.1
30.5
78.9
40.6
47.3
21.2
28.2
48.0
20.1
26.2
26.1
33.0
45.4
48.9
35.7
26.6
52.4
19.4”
29.9
36.0
18.0
36.5
25.0
125.4
130.8
25.7
17.6
18.3”
25.5
14.0
2
3
4
5
6
7
8
48.0
19.8
26.4
26.2
32.9
45.3
48.9
35.5
25.9
52.1
19.3”
29.8
35.9
18.0”
34.8
21.0
145.7
126.7
173.0
11.9
18.1”
21.2
25.8
12
13
14
1.5
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
29.0
35.2
11.4”
34.6
24.6
141.0
129.0
144.8, 144.0 145.0
131.2
173.2
12.4
18.4”
26.4
127.0
173.0
56.0
17.4”
20.6
11.9
17.7”
21.1
25.6
14.5
25.4
*Multiplicities assigned from DEPT spectrum.
“Assignments in any vertical column may be. interchanged.

Triterpenoids from
indica
1475
proton singlet at 4.36 attributable to an allylic primary
hydroxyl. The above spectral data can be accommodated
only if compound E has the structure
the chromatography are shown in Table 3. The acidic fraction
(20 was subjected to CC and the results are given in Table 4.
The
extract yielded only mangiferin (15
mp
acid (6). This structure was fur-
ther confirmed by its mass spectrum which lacked a
molecular ion but showed an ion at m/z 436 [M- 18
Identification of the known compounds was based on their
physical and spectral characteristics and comparison (TLC,
NMR, mmp) with the authentic samples wherever possible.
The ion at m/z 314
and the corre-
sponding fragment due to loss of side chain at m/z 175
clearly confirmed the presence of one
Compound A. Identified as
crystallized from as colourless prisms, mp
c 1) (Found: C, 80.95; H, 11.75.
(1). Re-
hydroxyl in rings AB and the other hydroxyl in the side
chain terminating with an a&unsaturated carboxyl
group.
for
C, 81.08; H, 11.71%).
(90 MHz,
s), 0.93
60.33 and 0.57
Hz),
s), 0.98
Firm evidence in support of the proposed structure of
1.23
s), 3.18
304 297
MS m/z (rel. int.): 444 [M]’
this new compound E (6) was obtained from its
spectrum (Table 2). The chemical shifts of C-l (6
NMR
C-5
315
Acetylationofcompound A. Compound A (50 mg) was
with 2 ml (1: 1) at room temp. overnight.
Usual work-up gave a product which showed two spots on TLC
203
175
95 (100).
(6
C-29 (6 20.6) and C-30 (25.4) clearly confirmed
the a-axial hydroxyl at C-3. The triplet at 56.0 con-
firmed the allylic primary hydroxyl at C-27.
It is noteworthy that there is great variation in the
triterpenoid constituents of the stem bark of the two
(R, 0.8 and 0.41 in
gel with
They were separated by CC on silica
to yield 4mg of dehy-
varieties (Banganpalli and Neelum) of
indica which we
dration product (lb), mp 98-100”; IR
1735, 890.
Hz),
have examined so far. One of the significant variations is
that several dammarane triterpenoids have been isolated
NMR (90 MHz,
60.32 and 0.57
from Banganpalli variety
but no dammaranes could
m), 4.78
s) and with benzene to give 40mg of diol
be detected in the Neelum variety.
monoacetate (la), mp
Compound B. Identified as
[a]$’ + 52” (CHCI,; c 0.7).
(2).
Recrystallized from
as colourless crystals, mp
EXPERIMENTAL
(CHCI,; c 0.8). (Found: C, 80.82; H, 11.60.
for
Mps:
The plant material was collected from an aged
C
H 0 : C, 81.08; H, 11.71%).
30
3500, 3000,
NMR (90 MHz, CDCI,): 0.76
2
tree at Lakshmaneswaram, near Narasapur in Andhra Pradesh,
India.
and 860.
Extraction and isolation procedure. The dried and powdered s), 1.09
stem-bark (6 kg) was extracted successively with n-hexane (bp
and in a large aspirator bottle. The dark brown
n-hexane extract was evapd under red. and the
s), 3.18
Acetylationofcompound B. Compound B (25 mg) was treated
with 1 ml (1: 1) at room temp. overnight. The
usual work-up followed by recrystallization from
gave colourless plates 18 mp
NMR (90 MHz, CDCI,): 60.78
s), 0.92 s), 0.94 s), 1.02
s), 4.42
resultant gummy residue (70 was separated into acidic,
and neutral fractions by adopting the procedure of ref.
The neutral fraction (30 was chromatographed on a silica gel
(500g) column and eluted successively with n-hexane,
(CHCI,; c 0.8).
0.89
s), 0.85
1.10
s),
1.98
m).
A
and
mixtures. The results of
Action of thionyl chloride on
of (12 mg) in dry
Table 3. Triterpenoids isolated from the neutral fraction of the M. indica extract
Fractions
Compound
Yield (g)
n-Hexane
Waxes
5.0
4.2
0.65
1)
1)
31-38
39-50
Cycloartenol
a- And
1)
3)
2)
0.2
61-65
6670
Intractable gum
0.06
: 1)
: 3)
71-80
81-85
86-92
Intractable gum
Intractable gum
C-24 Epimers of
0.15
0.08
0.12
3.0
93-98
99-106
107-125
126-131
132-135
136140
141-150
151-157
158-160
161-170
0.5
Compound
Intractable gum
Compound B
C-24 Epimers of
C-24 Epimers of
Compound C
A
(19: 1)
(9: 1)
(4: 1)
(4: 1)
(7: 3)
(1: 1)
0.03
0.05
0.4
0.01
Intractable gum

1476
V. ANJANEYLJLU et al.
Table 4. Triterpenoid acids isolated from acidic fraction of
extract
Yield (g)
Fractions
Compound
l-20
21-30
31-50
51-55
1)
(19: 1)
(19: 1)
(9: 1)
(9: I)
4.5
Mangiferonic acid
Intractable gum
Isomangiferolic acid
Mangiferolic acid
gum
0.4
7.0
69-100
101-105
(9:
0.1
0.03
(4:
(4: 1)
-EtOAc (4: 1)
(7: 3)
Compound D
Mixture
Intractable gum
Compound E
116-120
121-126
127-132
133-136
0.06
Hydroxymangiferolicacid
0
.
0
2
Intractable gum
(1: 1)
pyridine (1 ml) was cooled to 5’ and freshly distilled
(0.2 ml) was added with shaking. The usual work-up
gave
1) found
recrystallization
gave the diacetate (4b) as colourless plates
from
usual
work-up
followed by
followed by recrystallization from
less needles, mp
(10 mg). mp
s), 2.02
NMR (90 MHz, CDCI,): SO.32 and 0.55
+ 51” (CHCI,;
Hz), 0.85
2.06
0.92
4.68
s), 0.97
s). 5.02
1.87
6.85
identical in all respects with authentic
C. Identified as
acetate (2b).
(3). Recrys-
tallized from
as colourless needles, mp 253-255”.
Mixture I. This was
a
mixture of
or
or
(Found: C, 78.35; H, 10.36. C H 0 requires: C, 78.60; H,
acid
and
30 52
‘: 3550. MS m/z (ref. int.): 442
10.48%).
427
cm-
406
189
139
acid (5b): m p
1690, 1640.
60.30 and 0.50 (cyclopropane
0.98 (methyls), 1.82 s), 1.85
424
399
187
135
C. Compound C (7 mg) was dissolv-
ed in pyridine (0.5 ml) and acetylated with (0.5 ml) at room
temp. overnight. The usual work-up followed by recrystalliz-
355
175
121
287
171
59 (100).
223
167
207
157
IR
cm
3 5 0 0 ,
205
153
193
149
(200 MHz,
methylene),
(3H. s), 3.25, 3.45, 3.60 and 3.70
protons of hydroxyls), 6.57
472
peaks and geminal
r). MS m/z (rel. int.):
d), 6.90
ation from
gave colourless plates
c 0.5). cm
SO.71
1.16
6 mg), mp
1725.
408
385
357
355
354
175
332
315 (5).
35”
NMR(270
0.95 s), 0.99
2.00
203
121
202
95
189
55 (80).
149
135 (56). 123
1.18
1.96
int.): 526 [M
391
201
95
4.65 (I H, dd), 4.57 (1 H, dd). MS
Compound E. Identified as
26-oic acid (6). Recrystallized from
short needles, mp
(Found: C, 76.12; H, 10.09, C H 0 requires: C, 76.27; H,
10.17%). IR
511
as colourless
(CHCI,;
0.8).
295
175
255
161
43 (100).
Compound D. Identified as
acid (4). Recrystallized from
227
147
207
205
203
189
81
133
121
59
48
4
3550,
11200).
J = 4.2 Hz), 0.86
br s), 4.36
423
1695 and 1645:
or
as
0.8).
and 0.53 (2H
0.99
int.): 436
315
108 (22). 107
0.88 (3H. 0.96
colourless threads, mp
(Found: C, 76.18; H, 10.11;
1 0 . 1 7 % ) .
nm: 218
+ 27.5”
s), 3.48
s), 7.0
MS m/z (rel.
requires: C, 76.27; H,
1690 1640.
413 (2). 412
411
109
408
3500
314
215
105
203
175 (46). 129
‘HNMR (200 MHz, CDCI,): 60.32 and 0.50
57 (6).
Hz), 0.84
3.41
0.86
s), 0.92
s), 0.97
MS Acknowledgements-We wish to thank Dr A. Sree (Scientist,
m/z (rel. int.): 472
457
332
189
454 (1 440
436
257 (2). 255
109
421
Regional Research Laboratory, Bhubaneswar, India), for pro-
viding optical rotations for some of the compounds. One of the
411
385
209
55 (82).
355
403
315
297
232
175 (62). 123
95
authors
is grateful to CSIR, New Delhi, India, for the
award of a Fellowship.
D. Compound D (40 mg) in
at overnight. The usual work-
up followed by repeated recrystallization from
gave colourless plates 25 mp
(CHCI,; 1.5). NMR (90 MHz,
Hz), 0.89 s), 0.97
s), 3.78
(3 ml) was treated with
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