Trisulcusine: A novel spiro quinazoline alkaloid from ...nopr.niscair.res.in/bitstream/123456789/22101/1/IJCB 41B(11) 2385 … · Vol. 41 B, live mber 2002. pp. 2385-2389 Trisulcusine:

Indian Journal of Chemi stry Vol. 4 1 B, li ve mber 2002. pp. 2385-2389

Trisulcusine: A novel spiro quinazoline alkaloid from Anisotes trisulcus

Ad nan J AI-Rehail y, Khalid A EL-Sayed l, Mansour SAl-Said & Bahar Ahmed*

Medicinal: Aroma ti c and Poisonous Plants Research Center (MAPPRC), and Departmcnt of Pharmacognosy, Co llcge of Pharmacy, King Saud Uni versity, P.O. Box 2457, Ri yadh 11 45 1, Saudi A rabia ; ICurrent address: T he School of Pharmacy, Uni versity o f Mi ss iss ippi , MS 38677, U. S. A.

" Tel.: (966)- 1-467 -72 10. Fax: (966)- 1-467-7245, E-mail: bailmc<i @ksu.cdu.sa, [email protected] lll

Received] I Jllly 2001 ; accepled 25 DC/abel' 2001

Tile aerial parts of Allisoles IrislI/ells L. (N . O. Acanthaceae) have afforded a new spiro quinazoline alkaloid , characteri zed as 4, 5, 7- trihydro-3, 2'-spiro-[( I '-oxolo)-benzopy r-3 '-onel -pyrnlio-[4, 5-bl-quin :1Z0Iine by chemica l and spect ral methods and has been des ignated as trisu lcusine 1. In add ition, the previously reportcd alkaloids, namcly, pegan inc 2, vas icinone 3 and 5-mcthoxypeganine 4 have also been isolated and characteri zed.

AnisOles lrisulcus L. (N. O. Acanthaceae) commonl y known as A111l0dh, Madh, Maze and Maddaid' is wi ldl y distributed in the southern parts o f Saudi Arabi a particul arl y in the area of rocky wadi of Jabal Abu Hassan between Abha and Najran 2. It is used as traditional herbal medi cine in the Arab ian Penin sul a as antidi abetic3 bronchod ialator, hypotensive, and as an anti-hepatotox ic in the trea tment of all hepat ic conditi ons, including Jaundi ce, hepatiti s. ga ll stone and other hepati c disorders4

. The previous ph ytochemical reports on the plants have indi cated the presence of known alka loid s namely ani sotine, vas icinone, pega nine and vasic ino lone5 Pre liminary pharmacologica l studi es o f the pl ant have also show n increase in respirati on and local anaestheti c e ffect6 .

The pharmacognosti cal studi es have also revealed some important di agnos ti c features of the pl ant7

. We now report here in on the iso lati on of a nove l spiro quinazoline alkalo id named as tri suicu sine 1, wh ich has been characterized as 4 , 5, 7-trihydro-3, 2'-spiro­[( I'-oxolo )-benzopyr-3'-one ]-pyrralo-[ 4,S-b ]-qui nazo­line on the basis o f spectroscopic studies. Tn addition , the prev iously reported alkaloids, namely, peganine 2, vas icinone 3 and S-methoxypegan inc 4 have a lso been isolated and characteri zed for thi s source.

Results and Discussion Compound 1 named as tri sulcusine was obtained as

co lourless needl es and had the molecul ar compos iti on C'SH'4N102 as establi shed on the basis o f HRMS (M+ 290.3243), elemental analysi s, l3C_NMR and DEPT spectra. It gave a positive Dragendroff' s tes t for alkaloids and ex hibited absorpti on bands at 1630

2 Pegan ine, X= H2 , R" R2= H, R3= OH

3 Vasicinone , X= 0 , R" R2= H, R3= OH 4 5-Methoxypeganine, X= H2 , R,= OMe,

R2= H, R3= OH

(C=N), 1320 (-N <) due to alk aloidal terti ary nitrogen and 17 10 (C=O) cm" due to a carbonyl function in its IR spectrum. The UV spectrum showed absorption bands at 232 , 259, 301 and 396 nm indi cating the presence of aromatic and/or conjugated sys tem in the

' 3 S molecule. The C-NMR and DEPT spectra showed 18 carbon atoms for the molecule consisting of three mcth ylenes, eight aromatic methines, one carbony l and six quaternary carbon atoms (in total C 'SH I4 )

(Table 1). The 'H NMR spectrum also showed six signals at () 2.26 (tH, dd, J=9.0, 9.5 Hz, gemin al coup ling, H-4a), 2.44 (tH, ddd, J=II .O, 5.5 , 4.0 Hz, geminal and vicinal coupling, H-4b), due to methylene group at position-4; 3.27 ( I H, dd, J=9. 0, 9.5 Hz, geminal coup ling, H-Sa), 3.79 ( I H, ddc! , J=14.0 , 5.0 , 2.5 Hz, geminal and vicin al coupling, H-Sb) due to methylene group at positi on-S and 4.65

2386 IND IAN 1. CHEM ., SEC B, NOVEMBER 2002

Table I-I D-NMR data of trisulcusinc 1

Posi ti ons ' H NMR* DC NMR

I

2

3 (spiro carbon

i.c. C-2')

4a 2.26 dd

(9.0, 9.5)

4b 2.44 ddd

Sa ( I 1.0, 5.5 , 4.0)

3.27 dd

(9.0, 8.5)

5b 3.79 dddd

6 7a

7b

8 9

10

I I

12

13 I'

2' (spi ro carbon

i.c. C-3)

3'

4'

5'

7'

8'

9'

( 14.0,5.0,2.5)

4.65 d

( 13.0)

4.79 d

( 13.5)

6.92 d

6.99 dt!

(7.0,8.0)

7. 10 d

(7.5,7.5)

7.03 d

(8 .0)

7.56 dd

( I D.O, 3.0)

6.82, dd

(7 .0,8.0)

7.35 dq

(7.5 , 4.0,3.5, 8.0)

6.88 d

(9 .0)

159.5

73. 1

3 1.2

47.8

47.9

125 . 1

128.8

124.9

144.5

119.8

200.9

125.4

120.0

137.8

11 3.9

163 . 1

11 9.7

DEPT**

C

C

CH

CH

CH

C C

C CH

CH

CH

CJ-J

C

C *Assignillents wcrc bascd on ' J-J - 'H- and ' H-I.lC-COSY, and HMQC cxpcrimcnts: coup ling constants in Hcn,. arc given in parcnthcses : s: singlct, d: doublct; Mct hylcne diastcrcotopic protons cx hibi tcd diffcrcnt 0" in ' J-J -NMR and sa illc OC, but diffcrcnt signal s in IJC-NMR. ** DEPT chcmical shifts arc presentcd at () = 3)"[/4 whcn me th ylcnc groups rcachcs ncgati vc maximum.

( IH , d, J=1 3.0 Hz, geminal coup ling, H-7a), 4.79 ( IH , d, J=1 3.S Hz, geminal coupling, H-7b) due to methy lene group at position-7. The gem inal and

vic inal couplings due to H-4 and H-S indicated that the methy lene groups at positi on 4 alld 5 are adjacent to each other and are in the same ring.

The protons at position-7 did not show vicinal coupling, but exhibited on ly geminal coupling between H- 7a and H- 7b, which indicated that the third methylene group was present in another ring and could be placed at position-7. The other peaks in the IH NMR spectrum were also consistent with four aromatic protons of ring-A and four aromatic protons of ring-B exhibiting signals at b 6.92 (l H, d, .1=8.0 Hz, H-8), 6.99 (lH, dd, J=7 .0, 8.0 Hz, H-9), 7.10 (lH, dd, J=7 .S, 7.5 Hz, H-IO), 7.03 (lH, d, J=8.0 Hz, H-II ) due to protons ofring A and at 0 7.56 (l H, dd, J= I 0.0,3.0 Hz, H-4'), 6.82 (lH, dd, J=7 .0, 8.0 Hz, H-5'), 7.35 ( IH, dq, J=7 .S, 4.0, 3.5, 8.0 Hz, H-6'), 6.88 (I H, d, J=8.0 Hz, H-7') due to protons of ring B (Table J). The ass ignments of protons and carbon atoms were made with the help of IH_IH COSY and IH_ I3C COS Y (HMQc) experiments Cfable II ), which ex hibited correlations of H-4a (bH 2.26, be 31.2) with H-4b (2.44, 31.2), H-Sa (3.27,47.8) and H-Sb (3.79, 47.8); H-4b with H-4a, H­Sa and H-Sb and proton at 7a (4.65, 47.9) with H-7b (4.79, 47.9) and H-7b with H-7a. The methylene protons at positions 4, 5 and 7 were found diastereo­topic as they ex hibited non-equivalem chemical shi fts in IH NMR'J" and separate signals but with equi valent chemical shi fts in 13C NMR (HMQC) and thus could be differentiated by a and b at each position9b

. Tn the same way other protons in the aromatic region were also correlated together with protons in rings A and B. However, there was no correlation together between protons of ring A with ring B, which indicated that the two aromatic rings were not attached directly with each other. The IR spectrum showed an absorption band at 1110 cm·1 due to C-O (aromat ic) group, which was further substantiated by IJC MR spectrum ex hibiting a peak at Oc 163. 1 in downfield reg ion indicating that C-8' of ring B was attached to the oxygen atom of the spiro ring E. Had it been linked with other atom (e.g., nitrogen) rather than oxygen it wou ld not have been so down fi eld . Further, the absorption band at 1020 cm-I indicated also the presence of C- O (aliphatic) group, which cou ld be linked with spiro carbon at position-3 (i . e., at position 2' of ring E) exhibiting signal at 0 73. 1 in L'C NMR. It was, therefore, concluded that the oxygen atom was included in spiro ring E as ether linkage between C-3 and C-8' as indicated further by a strong absorption at 11 60 - 1140 cm-I in lR spectrum for an aromatic­aliphatic et her.

AL- REHAILY el al.: A NOVEL SPIRO QU INAZOLI NE ALKALOID FROM ANISOTES TRISULCUS 2387

Table 11- 2 D-N MR data of trisulcusi nc 1

Protons IH_I H COSY HMQC*** HM BC****

I

2

3 (spiro carbon i.e. C-2')

4a

4b

Sa

Sb 6

701 7b

8

9

10

I I

12 13

I '

2' (spiro carbon i.e. C-3))

3'

4'

5' 6' 7'

8' 9'

I H-I H Correlati on

H-4b, H-S01, H-Sb H-Sa, H-Sb, H-4a

H-Sb, 1-1 -4a

I-I-Sb, 1-1-4a, 1-1 -4b

1-1 -7b 1-1 -7b

1-1 -9, 1-1 - 10

1-1 -10

1-1 - 11 , 1-1 -9

1-1 - 10

1-1 -5' 1-1-6'

1-1-7', 1-1 -5'

1-1 -6 '

2JCH

3J CH

I S9.S S

73. 1 s

3 1.21 C-3, C-2, C-7 '

47.81 C-4 , C-3, C-2 , C-7

C-4

47.91 C- 13 C-S , C- 12, C-2, C-8

C- 13 C-S, C- 12, C-8

126.3 d C-7, C- IO, C-12

12S .1 d C- 13, C- I I

128.8 d

124.9 d C- 13, C-9

144.S s

119.9 s

200.9 s

12S.4d C-6', C-8', C-3'

120.0 d C-7', C-9'

137 .8 d C-8', C-4'

11 3.9 d C-9', C-5'

163. 1 s

11 9.7 s

***C-multiplic ities were estab li shed by DEPT experiment.

****The correlat ions in I-I MBC have been shown from protons to carbons.

The HMBC ex perime nt di spl ayed lo ng-range couplings e l m and 3 l CH) between the carbon of carbonyl fun ction (200.9) and protons of meth ylene group of positio n-4 of ring D and HA' of ring B; the protons of pos iti on-4 a lso showed long- range couplings with C-3 (73. 1) and C-2 ( 159.5); the protons of positi on-5 with C-4 (3 1.2), C-3, C-2 and C-7 (47. 9) (Table II), whi ch could place the spi ro carbon at pos ition-3 between rings D and E and carbonyl function at positio n-3' of ring E. T he proto ns of r os ition-7 a lso d isp layed long-range couplings with C-8 ( 126 .3) , C- 13 ( J 19.8) and C- 12 ( 144.5) of rings A and with C-2 ( 159 .5) o f rings C and 0 Ind icating that the methylene group at posit ion -7 was con nected to ring A and D. T he nitrogen ato ms wert' thus placed at pos ition -1 and 6 of ring C as have been found in o ther related quin azol ine alhlo ids of

the plant containing vas ic ine mOieti o. T he long-range couplings of rings A and B were also corre lated, where in no corre lations were fo und between the protons of ring A with protons of ring B indicati ng again that rings A and B were not connec ted to each o ther. However, the corre latio ns of protons of rings J\ and B were fo und with protons o f the respect ive ri ngs, which have been presented in Table II and Figure 1.

The mass spectrum of the compound a lso supported the proposed structure, whi ch ex hibi ted prominent peaks characte ri sti c o f qui nazo li ne a lka lo ids conta ining vas ic ine mo ieti O at mlz 144 (spec ies c) due to fragment ori ginated by ruptu re of ring D; rnlz 130 ion orig in ated by the e liminati on o f C H: g ro up fro m species c; mlz 169 (species a) due to fragment produced by the e liminatio n of rings E and B at spi ro carbon; mlz 156 (spec ies b) d ue to ru pture

2388 INDI AN J. CHEM., SEC B. NOVEMBER 2002

Figure 1- Helcrol1u<.: lca r Illu ll iple bond corrclalions( HM BC) for lri sulcusinc I , arrows poinl fro III prolons 10 ca rbons

of rings D; lIl/z 13 1 (spec ies d) due to ion produced by the removal of ring E and B at spiro carbon. Other peaks in the mass spectrum were also supportive to the proposed structure of the compound (Scheme I). Thus, on the bas is of above chemical and spectral studi es the st ructure of compound 1 was elucidated as 4,5,7 -trihydro-3, 2' -spiro-[( 1 '-oxolo )-benzopyr-3 ' -one]­pY ITalo-r4,5-b]-quinazoline and has been des ignated as tri sulcusine 1.

The oth r compounds namely peganine 2, vas icinone 3 and 5-methoxy peganine 4 were also characteri zed by thei r spectral studies and compared with the reported va lu es in the literature10.1:l .

Experimental Section General procedure. Melting points were

detenn i ned on Metl er 9100 Electro thermal apparatus by open cap i ll ary method and are uncorrected. The IR spectra were recorded as KBr pellets on PYE UN ICAM Spectrophotometer. The UV spectra were measured in chloroform on UV- 160 IPC UV-v is Spectrophotometer. The optical rotat ion was recorded in chl oroform on Perkin-Elmer 24 1 MC Po larimeter. The mass spectra were recorded on a Fi nnegan MAT 300 mass spectrometer. The IH (500 MHz) and 13C and DEPT 90 and 135 NMR (125 MHz) and 2D

MR (COSY, HMBC and HMQc) were recorded on Bruker DR X 500 spectrometer in CDCb using TMS as internal standard reference, chemi ca l shift in 0 (ppm) and oupling constants (J values) are in Hz. The chromatography (Centrifugal Preparative TLC) was performed on a Chromatotron of Harri son Research Inc., USA using 4 mm rotor and silica gel PF-254 with CaS04.1h H20 as an adsorbent. TLC were pelformed on sili ca gel 60 F254 Merck plates

m/z 289

O~.l

\---0

m/z 131 \ \ species d

~+

I'" //

m/z91 species e

Trisu lcus ine (1 ):C1sH'4NP2 (M+ 290)

Scheme I

and sprayed with Dragendroff' s reagent for visuali zati on of the spots.

Plant material. The aeri al parts of AnisOles trisulcus were coll ected on March 14. 1998 from AI­Jawah, 40 km form AI-Baha towards west region of Saudi Arabia and identi fied by a taxonomist Dr Sultanul-Abid in , Medicinal , Aromatic and Poisonou. Pl an ts Research Center (MAPPRC), Department of Pharmacognosy, College of Pharmacy , King Saud Un iversity , Ri yad h, Saudi Arabia. A voucher spec imen no. 13830-A has been deposited in the herbari um of the center for future reference.

Extraction and isolation. Air dri ed aerial parts (8 .5 kg, leaves and stems) were crushed to coarse powder and extracted thri ce with 95 % alcohol (10.0, 8.5, 8.5 , L) along with a few mL of ammoni a by a cold percolation . The alcohol1c ex trac t was concentrated and dried under red uced pressure to get a viscous mass (390 g). It was then extrac ted thri ce with 2% HC] (3x4.0 L), warmed and st irred and su bsequently ex tracted thrice with ch loroform (3x4.0 L) to remove non-alkaloidal materi al (120 g). The aq ueous layer was made alkal ine with ammon iu m

AL-REHA IL Y et al.: A NOVEL SPIRO QU INAZOLI NE ALKALO ID FROM ANISOTES TR ISULC US 2389

hydrox ide to pH 6 and thell ex tracted with chlo roform

(3x4.0 L) and marked chlo roform extrac t no. l . T he aqueous layer was made more a lkaline with am monium hydrox ide to pH 9 and subsequentl y

ex tracted with chloroform (3x4.0 L ) and marked chloroform extract no.2. The mother liquor was then

ex tracted thrice with ethyl ace tate (3x4.0 L ). Isolation of compounds. The chl oroform fract io n

no. I was concen trated and dried ( 1.5 g) and then chromatographed on a Chromatotron, which was first e luted with acetone-chl oroform-acet ic ac id ( I :9:2 drops ; 100 mL. ) to remove a ll non-alk a lo idal matte rs. After drying it was e luted with acetone-chl orofo rm­ammonia (3:47:few drops), which affo rded co mpo und 1 (8.0 mg). The chl oroform fraction no.2 (5.4 g) was chromatographed in the same manner o n a Chromatotron, which on e luti on with 15% acetone­chloroform-a few drops of ammon ia affo rded peganine 2 ( 140 mg), and with 4% ethano l in chloroform and a few drops of ammo ni a gave vas ic inone 3 ( 180 mg) . The eth yl acetate fract ion was concentrated and dried (1.6 g) and then chromatographed o n a Chromatotron, whi ch on e luti on with 2% methanol-dichloromethane- a few drops of ammon ia affo rded 5-methoxy peganine 4 (8.0 mg).

Trisulcusine 1: Obtained as co lourl ess needles (CHCI3); m.p. 235-236°C (dec.); [a]D - 200 (c 0.02, CHCh); UV (CHCl3) Am"X (l og e): 232 (3 .35), 259 (2.75),301 (2 .76),396 (2 .32) nm ; IR (KBr) Villa x : 2850 (C H2), 1710 (C=O), 1630 (C=N), 1600, 1560 (C=C), 1470, 1340, 1320 (-N<) , 1160, 11 40 (-O-ether), 1110 (C-O, aromati c) , 1020 (C-O alcoho l ic), 900, 740, 720 (C=C) cm- I; 10 and 20 NMR data , Tables I and II ; ElMS (70 eV) mlz: 290 [M +, C I8H I4 20 2] (23), 289 (95), 260 (6), 239 (1 4), 232 (12), 207 ( II ), 180 (6), 169 ( 100), 156 (5) , 144 (20), 130 (10), 13 1 ( 12), 11 6 (14), 102 (8), 9 1 ( 12),77 (20), 65 (7),44(5); HRMS : mJz: 290 .3243 (M +) (Ca lcd . for C 1 HH 14N20 2.

290.3234); (Found : C, 74.33 ; H , 4.75; N, 9.53 ; 0 , 11.39. C IsHI 4N20 2 requires C, 74.47, H, 4.86 ; 9.65; 0, 11.02%).

Peganine 2, vas icinone 3 and 5-methoxy­pega nine 4 were a lso characte ri zed and the ir chemica l and spectra l values were compared with the repo rted values in the lite rature 1o.13.

Acknowledgement The authors are thankful to Muhammad A. Mukhair,

for hi s technical ass istance and to Dr C harles D. Hufford, Department of Ph armacog nosy, School of Pharmacy, University of Mi ss iss ippi , for taking the spectra of compounds.

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