Furoquinoline alkaloids from the leaves of Melicope confusa

Arch. Pharm. Res. 9(11, 11,,,13 (19861

Furoquinoline Alkaloids from the Leaves of

Melicope confusa

Sam Sik Kang and Won Sick Woo

Natural Products Research Institute, Seoul National University, Seoul 110, Korea (Recewed March 12, 19801

Abstract F~ln addition to the previous reported furoquinoline alkaloids, skimmiani~e, kokusagmine and

confusameline, a rare furoquinoline alkaloid, heliparvifolme, mp 241-3 ~ was isolated from the leaves of

Mellcope con/usa and characterized by spectral data.

KeywordsDMehcope contusa, Rutaceae. Furoquinoline alkaloid, Skimmianine, Kokusagmme, Confus- ameline, Heliparvifoline.

This paper describes the results of our investigation

on the furoquinoline alkaloids of Melicope confusa (Rutaceae), which is distributed in Taiwan.

Recrystallization of the alkaloidal fraction from the

methanol extract afforded the major alkaloid as stout

plates, mp 177-8 ~ which was identified as skimmianine (I) by direct comparison with an authentic sampleJ 1 The

mother liquor was subjected to SiO~ column chroma-

tography eluting with benzene-ether mixture to give

kokusaginine (II), mp 170 ~ confusameline (III), mp

250-2 ~ , which were identified by comparison of their

physical and spectral data with those appeared in literature, 21 and a minor alkaloid (IV), which has not

been reported in this plant.

The minor compound (IV) crystallized from methanol to afford stout plates, mp 241-3 ~ exhibited a

maximum peak at 248nm with fine bands in the region

of 301-337 nm in uv spectrum which were shifted to a

longer wavelength accompanied by loss of fine structure

in acidic medium, typical of a furo [2,3-b] quinoline system in its structure. 3J Its ir spectrum also showed

peaks for furan ring system at 3160, 3130 and 1096

cm -J41 which was supported by the presence of two sets

of doublets at 67.89 (J = 2.8Hz) and 7.36 (J = 2.8Hz) for

furan protons 51 in its nmr spectrum. A methoxy signal at 64.40 suggested the presence of 4-methoxy group 51

which was also supported by the intense peaks for M+-15 and M+-43 ions at m/z 230 and 20261, respective-

ly. Another methoxy signal singlet at 63.90 and two

singlets at 67.42 and 7.16 indicated that 6 and 7 posi- tions were oxygenated and one of them was methylated,

which was supported by the fact that methylation of IV with CH2N2 afforded kokusaginine (ll). In the presence

of a drop each of D~O and NaOD, the downfield proton (H-5) was shifted from 67.42 to 7.33, while the upfield

proton (H-8) was shifted from 67.16 to 7.01. Thus, the

hydroxyl group should be located at 7-position adjacent

to the proton resonating at 67.16. From the above facts

and by comparison of its physical and spectral data with those appeared in literature 71, compound IV was iden-

tified as heliparvifoline, which has only been isolated

from Helietta parvifolia.

EXPERIMENTAL METHODS

The mps were taken on a Mitamura-Riken apparatus

and are uncorrected. The ir spectra were determined in

KBr tablets on a Perkin-Elmer model 283B spectro-

photometer.and the uv spectra were runned with Gilford

System 2600 spectrophotometer. The nmr spectra were recorded at 80MHz on a Varian FT-80A with TMS as in-

ternal standard. Mass spectra were taken a Hewlett-

Packard 5985B GC/MS spectrometer operating at 70eV. Isolation of Alkaloids

Powdered leaves (650g) were extracted with MeOH and the MeOH extract was partitioned with 3 % acetic

acid and ether. The aqueous layer was basified with

c-NH4OH and exhaustively extracted with CHCI 3. The

combined CHCI 3 extracts was recrystallized from MeOH to give skimmianine (I) (4.8g) as stout needles. The mother liquor was chromatographed over SiO 2 column

eluting with benzene-ether mixture (9:1, 7:1, 5:1 and

then 4:1) to yield kokusaginie (II), skimmianine (I), con- fusameline 0II) and then heliparvifoline (IV) in the order

11

12 S.S. Kang and W.S. Woo

of elution.

OCH3

6 5

Ra

I R~ = H, R2 = R3 = OCH3

I R~=R~=OCH3, Ra=H

I]] Ri--R3=H, R2=OH

IV R~=OCHa, Ra=OH, 'Ra=H

Skimmianine (I)

mp 177-8 ~ [Lit. l) mp 177-8 ~

MeOH UV Area ~ nm (log e); 242(sh, 4.66), 250(4.81), 305(sh,

3.69), 321(3.86), 333(3.88), 344(sh, 3.76); ~. M~OH+HCl nm -- max (logd; 254(4.77), 322(3.85), 351(3.90).

ID U KBr 1 1 ~. ma,,cm- ;3 50, 3121(furan), 1619(C=C), 1269(ether),

1093(=COC). NMR(CDCI3, TMS)& 4.02(3H, s, OCH3),

4.11(3H, s, OCH3), 4.42(3H, s, 4-OCH3), 6.99(1H, d, J--- 2.8Hz, furan g-H), 7.18(1H, d, J=9.5Hz, H-6), 7.53(1H, d, J=2.8Hz, furan a-H), 7.97(1H, d, J=9.5Hz, H-5).

MS, m/z(rel, int).: 259(M § 34.6), 248(M + -H, 13.6), 244

(M § -CH 3, 100), 230(M +-HCO, 65.4), 216[M +-(CH. + CO) 31.9i, 201(216-CH 3, 51.3), 200(230-CH20, 16,8), 199