Triterpenes from Adiantum lunulactum

Article abstract of DOI:10.1016/S0367-326X(02)00119-3

The petrol extract of the whole plant of Adiantum lunuactum yielded a new hopane triterpenoid characterized as 6α-acetoxy-16β,22-dihydroxy-3-ketoisohopane, along with the known 3β,6α,16β,22-tetrahydroxyisohopane (mollugogenol A). The structures were elucidated by spectral as well as chemical studies.

Full text of DOI:10.1016/S0367-326X(02)00119-3

Ž
.
Fitoterapia 73 2002 363᎐368
Triterpenes from Adiantum lunulactum
G. BrahmachariU, D. Chatterjee
Department of Chemistry, Vis¨a-Bharati Uni¨ersity, Santiniketan-731 235, West Bengal, India
Received 23 September 2001; accepted 8 May 2002
Abstract
The petrol extract of the whole plant of Adiantum lunuactum yielded a new hopane
triterpenoid characterized as 6␣-acetoxy-16␤,22-dihydroxy-3-ketoisohopane, along with the
Ž
.
known 3␤,6␣,16␤,22-tetrahydroxyisohopane mollugogenol A . The structures were eluci-
dated by spectral as well as chemical studies. ᮊ 2002 Elsevier Science B.V. All rights
reserved.
Keywords: Adiantum lunulactum; 6␣-acetoxy-16␤,22-dihydroxy-3-ketoisohopane; Mollugogenol A
1. Introduction
Ž
. w x
Adiantum lunulactum Burm, syn. Adiantum philippense Linn. Adiantaceae 1 ,
commonly known as walking maidenhair fern, is traditionally used in the treatment
of various diseases among the local and tribal people. The plant is mainly used in
blood diseases, epileptic fits, erysipelas, fever, dysentry, ulcers, febrile affections,
w
x
atrophy, emaciation or cachexy, muscular pain, rabies and elephantiasis 1,2 . The
present communication deals with the isolation and characterization of one new
hopane triterpene 2 and one known compound, mollugogenol A 1 from the
Ž .
Ž .
petrol extract of this plant.
U
Corresponding author.
Ž
.
E-mail address: brahmg2001@yahoo.co.in G. Brahmachari .
0367-326Xr02r$ - see front matter ᮊ 2002 Elsevier Science B.V. All rights reserved.
Ž
.
PII: S 0 3 6 7 - 3 2 6 X 0 2 0 0 1 1 9 - 3

( )
G. Brahmachari, D. Chatterjee rFitoterapia 73 2002 363᎐368
364
2. Experimental
2.1. Plant material
A. lunulactum was collected from the United Chemical and Allied Products,
Ž
.
Kolkata WB , India and taxonomically authenticated by a taxonomist of the
Botany Department of this University. A herbarium specimen is deposited in the
Natural Product Laboratory, Department of Chemistry, Visva-Bharati University,
Ž
.
Santiniketan WB .
2.2. Extraction and isolation
All mps are uncorrected.
Ž
.
Air-dried and powdered whole plant 1.5 kg was Soxhlet extracted with petrol
60᎐80Њ . The extract was concentrated under reduced pressure and then subjected
Ž
.
Ž
.
x
to Si-gel CC. Elution with petrol᎐benzene 1:4 afforded a mixture which on
further CC yielded mollugogenol A 1.8 g
Both compounds were recrystallized from aq MeOH.
Ž
. Ž . w
Ž . Ž
.
1
3,7 and then compound 2 3.6 g .
Fig. 1.
(
) Ž .
Mollugogenol A 3␤,6␣,16␤,22-tetrahydroxyisohopane 1 : C30 H52O4, white crys-
20
w x
Ž
.
Ž
.
tals, mp 250᎐2 ЊC; ␣
q59 c 1.0, CHCl3 ; IR bands KBr : 3400, 2936, 1050
D

(
)
G. Brahmachari, D. Chatterjee rFitoterapia 73 2002 363᎐368
365
Table 1
13
Ž
.
C-NMR data 100 MHz, CDCl3 of compound 1, 2, 2d
Carbon
1
2
2d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
38.7
26.7
78.2
39.1
60.1
67.7
42.6
42.5
49.1
38.8
20.6
23.4
47.2
43.4
45.4
67.3
57.4
46.5
39.4
25.8
51.9
70.9
30.1
16.1
15.3
17.4
16.9
17.8
28.9
30.6
39.5
33.9
40.4
18.4
43.6
33.4
61.1
69.2
45.3
42.8
49.5
39.1
20.9
23.9
49.5
41.6
44.9
66.8
57.4
46.2
39.3
25.5
51.4
70.7
29.8
21.8
15.6
17.1
17.3
17.7
28.2
30.2
218.1
47.2
58.4
72.1
41.5
42.6
49.2
39.4
21.0
23.9
46.8
43.1
45.2
67.2
57.2
45.9
39.1
25.4
51.6
70.7
29.2
21.9
15.7
17.8
17.2
17.5
28.6
30.9
Ž
.
Ž
.
Ž
.
OAc 6␣
172.1 C s O , 22.5 Me
1
cmy1; EIMS mrz: 476 M q, 458, 440, 422, 404, 400, 382, 364, 346, 59; H-NMR
w
x
Ž
.
400 MHz, CDCl3 : ␦ 0.73, 0.90, 1.01, 1.03, 1.06, 1.21, 1.25, 1.42 for eight tertiary
methyls, 3.98 1H, m, whr2 17 Hz, H-6ax , 3.72 1H, m, whr2 15 Hz, H-16ax , 3.21
Ž
.
Ž
.
13
Ž
.
1H, m, whr 2 15.5 Hz, H-3ax ; C-NMR: Table 1.
Ž .
6␣-Acetoxy-16␤,22-dihydroxy-3-ketoisohopane 2 : C32 H52O5, white crystals mp
20
D
w x
261᎐2 ЊC, ␣
Ž
.
Ž
.
q69 c 1.0, CHCl3 ; IR bands KBr : 3420, 2940, 1730, 1710, 1257,
1050 cmy1; EIMS mrz: 516 M q, 498, 457, 456, 425, 407, 252, 234, 219, 176, 264,
w
x
1
Ž
.
␦
263, 204, 203, 276, 224, 216, 223, 205, 208, 147, 59; H-NMR 400 MHz, CDCl3
Ž
.
Ž
0.82, 0.90, 0.98, 1.02, 1.05, 1.15, 1.42 6H,s for eight tertiary methyls, ␦1.98 3H,s,
OAc , 3.71 1H, m, whr2 16 Hz, H-16ax , 4.98 1H, m, whr2 15 Hz, H-6ax ;
.
Ž
.
Ž
.
13C-NMR: Table 1.

( )
G. Brahmachari, D. Chatterjee rFitoterapia 73 2002 363᎐368
366
2.3. Acetylation of compound 2
One gram of 2 was heated with Ac2O 20 ml and pyr 8 ml overnight. Usual
Ž
.
Ž
.
Ž
.
work up and Si-gel CC eluting with benzene, provided a colorless glass 280 mg ,
which was recrystallized from MeOH, C34 H52O5 2a , M
elution with benzenerchloroform 2:1 gave another glass 315 mg which was
recrystallized from aq MeOH, 2b , M mrz 558.
Ž
. w xq
mrz 540. Further
Ž
.
Ž
.
Ž
. w xq
( ) ( )
2.4. Hydrolysis of compound 2 to oxo-triol 2c
Ž
.
A quantity of 1.5 g of 2 was treated with 2% alcoholic KOH 40 ml overnight at
Ž
.
room temperature. Usual work up and crystallization from aq EtOH, yielded 2c ,
mrz 474, mp 256᎐7 ЊC, IR bands KBr : 3410, 2930, 1705, 1047 cm
H-NMR 400 MHz, CDCl3 : ␦ 0.82, 0.90, 0.98, 1.03, 1.04, 1.14, 1.35, 1.41, for eight
y1
w
xq
Ž
.
M
;
1
Ž
.
Ž
Ž
.
Ž
.
Ž
tertiary methyls, 2.30 2H, m, CH2CO , 3.92 1H, m, whr2 16 Hz, H-6ax , 3.70 1H,
.
m, whr2 17 Hz, H-16ax
.
( )
2.5. LAH reduction of 2c
Ž
.
Ž
.
A slurry of LAH 1 g in dry ether 50 ml was heated under reflux with a
Ž
.
Ž
.
solution of 2c 200 mg in dry ether 10 ml for 6 h. After decomposing the excess
reagent with ice-water, the product was treated with 2N H2 SO4 and then extracted
with Et2O, washed with water, dried and the solvent removed. The residue on
Si-gel CC 50 g furnished a compound 115 mg , C30 H52O4, M mrz 476, mp
250᎐1 ЊC, identified as mollugogenol A 1 .
Ž
.
Ž
Ž .
.
w
xq
( )
2.6. Wolff᎐Kishner reduction of 2c
Ž
.
Ž
Mg 252 of 2c in a mixture of absolute alcohol 20 ml and diethylene glycol 20
.
Ž
.
Ž
.
ml was refluxed with hydrazine hydrate 85%, 20 ml for 2 h. Solid KOH 4 g was
added and the solvent was distilled off until the mixture refluxed freely for 4 h.
After purification, a product was obtained, C30 H52O3 2d , M
Ž
. w xq
mrz 460, mp
20
D
w x
331᎐4 ЊC, ␣
Ž
.
Ž
. w
x
q51Њ c 1, py , found to be identical with leucotylin 2d 4᎐6 from
Ž
.
comparison of its physical and spectral properties; IR bands KBr : 3440, 2970,
2940, 1047 cmy1; H-NMR 400 MHz, CDCl3 : ␦ 0.75, 0.83, 0.96, 1.03, 1.04, 1.14,
1
Ž
.
Ž
.
Ž
1.22, 1.32 for eight tertiary methyls, 3.71 1H, m, whr2 16 Hz, H-16ax , 3.94 1H, m,
13
.
whr2 17 Hz, H-6ax . C-NMR: Table 1.
3. Results and discussion
Ž .
The compound 1 responded positively to the Liebermann᎐Burchardt test for
w
xq
triterpene. The EIMS gave a molecular ion M at mrz 476 consistent with a
molecular formula C30 H52O4. The mass spectral fragmentation of the compound is
w
x
closely similar to those of hopane type of triterpenes 3,7᎐10 ; showing significant

(
)
G. Brahmachari, D. Chatterjee rFitoterapia 73 2002 363᎐368
367
peaks at mrz 458, 440, 422, 404 due to the successive loss of four molecules of
water from the parent molecule and one intense peak at mrz 59, due to the ion
Me2CϭOHq, formed by the cleavage of the hydroxy-isopropyl moiety. Of the four
OH groups, three are secondary and one is tertiary. This contention was supported
by the resonances of four sp3 carbons at ␦ 78.2, 69.2, 66.8 and 70.7 in the 13C-NMR
spectrum and confirmed by 1H-NMR spectrum which showed signals for three
Ž .
secondary alcohols at ␦ 3.21, 3.72, 3.98. The compound 1 was finally identified as
Ž
.
3␤,6␣,16␤,22-tetrahydroxyisohopane mollugogenol A .
Ž . .
Žw xq
M mrz 516 , gave a positive response to the
Compound 2 , C32 H52O5
Liebermann᎐Burchardt test. Its IR spectrum showed characteristic absorption
Ž
.
Ž
.
Ž
bands at 3420, 1050 hydroxyl groups , 1730, 1257 ester carbonyl , 1710 six-mem-
bered cyclic ketone cmy1. The 1H-NMR spectrum displayed signals for eight
.
Ž
tertiary methyls at ␦ 0.82, 0.90, 0.98, 1.02, 1.05, 1.15 and 1.42 6H, assignable to the
methyl protons of hydroxy-isopropyl moiety ; a three proton singlet at ␦ 1.98
ascribable to an acetoxy group ; two proton multiplet at ␦ 2.30 suggesting the
.
Ž
.
presence of a keto-methylene function; a carbinol-methine proton at ␦ 3.71 and
one proton multiplet at ␦ 4.98 assignable to ) CH᎐OAc. The presence of these
functionalities in the molecules received support from the appearance of the
13
Ž
.
Ž
.
chemical shifts in the C-NMR spectrum at ␦ 218.1 CϭO , 72.1 C᎐OAc , 67.2
Ž
.
Ž
.
Ž
.
C᎐OH , 33.9 keto-methylene carbon , 172.1 and 22.5 OAc . On heating with
acetic anhydride and pyridine, 2 furnished two acetate derivatives 2a, 2b . Only
Ž .
Ž
.
2b gave a yellow color with tetranitromethane. The presence of isopropenyl group
1
wŽ
Ž
.
x
᎐C Me ϭCH2 in 2b was shown by its IR and H-NMR spectra. Its IR spectrum
showed bands at 1735, 1250 cmy1 acetoxy , 1640, 900 cm
y1
Ž
.
Ž
.
) CϭCH2 . Its
1H-NMR spectrum exhibited signals at ␦ 0.82, 0.90, 0.99, 1.06, 1.2, 1.25 for six
tertiary methyl groups; two singlets at ␦ 1.98 and 2.03 for two acetoxy groups; a
multiplet at ␦ 2.3 for a keto-methylene function; two multiplets at ␦ 4.95 and 5.1, a
w
Ž
.
x
sharp singlet at
␦
1.69 C᎐ CH3 ϭCH2 and
a
broad singlet at
␦
w
Ž
.
x
4.2 2H,᎐C CH3 ϭCH2 . The presence of a tertiary hydroxyl function in the other
y1
Ž
.
acetate derivative 2a was shown by the absorption band at 3500 cm in its IR
1
spectrum and by its resistance to oxidation. Its H-NMR spectrum showed sharp
singlets at ␦ 2.02 and 1.96 for two acetoxyl functions. The signals at ␦ 1.33 and 1.41
may be attributed to two methyl groups attached to carbon bearing the tertiary
hydroxyl group.
The positive Zimmermann test and the MS fragmentation suggest the location of
w
x
Ž .
the keto function at C-3 11 . The acetoxy function at C-6 of 2 is equatorial and
1
w
x
␣, as evidenced from the H-NMR signal at ␦ 4.98 3,7,11᎐13 . The tertiary
hydroxy group belongs to the hydroxyisopropyl moiety. The secondary hydroxy
group is equatorial and ␤ on the basis of its easy acetylation 14,15 and from the
resonance at ␦ 3.71 in the H-NMR spectrum 3,7,11᎐13,16 . The compound 2c on
w
x
1
w
x
LAH reduction yielded a tetrahydroxy derivative, C32 H52O4, identified as mollu-
Ž . w x
3,7 . The compound 2c on Wolff᎐Kishner reduction yielded a
gogenol-A
1
Ž
. w
x
trihydroxy derivative C30 H52O3, identified as leucotylin 2d 4,6 .
The reported experimental results and the 13C-NMR spectra reported in the

( )
G. Brahmachari, D. Chatterjee rFitoterapia 73 2002 363᎐368
368
Table 1 led us to formulate the compound 2 as 6␣-acetoxy-16␤,22-dihydroxy-3-ke-
Ž
.
toisohopane Fig. 1 .
Acknowledgements
Ž
.
Ž
.
The authors are grateful to RSIC, IIT Chennai and RSIC, CDRI Lucknow
for spectral measurements. They are also thankful to the United Chemical and
Ž
.
Allied Products Kolkata for supplying the plant materials and to Dr S. Mandal,
Department of Botany, Visva-Bharati University for verification of the plant.
References
w x
1
w x
Ambasta SP, Editor-in-chief. The useful plants of India. New Delhi: PID, CSIR, 1986:15.
Chopra RN, Chopra IC. Glossary of Indian medicinal plants. New Delhi: CSIR, 1956.
Chakrabarti P. Tetrahedron 1969;25:3301.
2
w x
3
w x
4
Yoshioka I, Nakanishi T. Chem Pharm Bull 1963;11:1468.
w x
5
Yoshioka I, Nakanishi T, Kitagawa I. Tetrahedron 1968;12:1485.
Yoshioka I, Nakanishi T, Kitagawa I. Chem Pharm Bull 1969;17:279.
Hamburger M, Dudan G, Ramachandran N, Jayaprakasam R, Hostettmann K. Phytochemistry
1989;6:1767.
w x
6
w x
7
w x
Ž .
Corbett RE, Young H. J Chem Soc C 1966;18:1556.
8
w x
Ž .
9
x
Corbett RE, Young H. J Chem Soc C 1966;18:1564.
w
10 Galbraith MN, Miller CJ, Rawson JWL, Ritchie E, Shannon JS, Taylor WC. Aust J Chem
1965;18:226.
w
x
11 Barton DHR, de Mayo P. J Chem Soc 1954:887.
w
x
12 Bhacca NS, Williams DH. Application of NMR Spectroscopy in Organic Chemistry. London:
Holden-Day, 1964.
w
w
w
w
x
13 Sharma M, Glick RE, Mumma RO. J Org Chem 1962;27:4512.
14 Schreiber J, Eschemnoser A. Helv Chem Acta 1955;38:1529.
15 Razdan TK, Kachroo V, Harkar S, Koul G. Tetrahedron 1982;38:991.
16 Huneck S, Lehn JH. Bull Soc Chim Fr 1963:1702.
x
x
x