Glucosides from Ligustrum vulgare L. 357

A Glucosidic Alkaloid Artifact, originated from Secoiridoid Glucosides from Fruits of Ligustrum vulgare L. Michael Willems*

Institut fur Pharmazeutische Biologie der Johann Wolfgang Goethe-Uni- versitat, Georg-Voigt-StraOe 16, D-6000 Frankfurt/Main, Bundesrepu- blik Deutschland

Received October 28, 1987

Secoiridoid glucosides from ripe fruits of Ligustrum vulgare L. treated with 5 % H,SO. and NH, could be converted easily in pyridine deriva-

Ein glucosidisches Alkaloid-Artefakt aus Secoiridoidglucosiden von Ligu- strum vulgare L.

1 "

t ive~ ' .~* 3). Recently LA 9, novel glucosidic alkaloidartifact has been iso- lated. Its structure [I1 has been established, primarily on the basis of IR-, NMR- and mass spectral data.

Secoirido~glucoside aus reifen Friichten Ligustrum vulgare L. kiin- nen bei Behandlung mit % H,SO, und NH, leicht in Pyridin-Derivate uberfuhrt werden'. 2, 3). Kurzlich wurde LA 9, ein neuartiges glucosidi- sches Alkaloid-Artefakt isoliert. Seine Struktur [ 11 wurde in eriter Linie anhand von IR-, NMR- und massenspektrometrischer Daten bewiesen.

Continuing the investigations about alkaloid artifacts generated by am- monia and secoiridoid glucosides from ripe fruits of the common privet') (Ligustrurn vulgare L.), a novel glucosidic pyridine alkaloid LA 9 (1) has been isolated. After the series of non glucosidic monomeric pyridine alka- loids LA I , LA 2 (3), LA 6 (2) and Jasmininez) and dimeric pyridine alka- loids LA 4 and LA 531, a glucosidic type of artifacts will be described for the first time.

2 i , P

H O W o R

4 : R = H 5: R = GLc

3

An ethanolic extract of ripe fruits enriched with secoirido- id glucosides'), was treated with 5 % H,S04 and subsequent- ly with NH,. Extraction with CH,Cl, and column chromato- graphy of the concentrated CH,Cl, fraction on silica gel yielded 1. Its colourless crystals (m.p. 64-66 "C, uncorr.) have a piquant bitter flavour. The PI-FAB-mass spectrum shows a pseudomolecular ion peak at m/z = 506 [M+Hlt and after addition of Lil at m/z = 5 12 [M+Lil+ indicating the molecular weight to be 505, corresponding to the molecu- lar formula C25H31NOlo. FeCl, or Folins reagent indicated a free phenolic OH-group. This is in accordance with the ab-

sorption at 3400 cm-' in the IR-spectrum. Further important signals occur at 1728 cm-' (ester) and in the range from 15 18 cm-' to 16 17 cm-', suggesting conjugated double bonds and conjugated, cyclic -C=N- bonds. The signals of the 'H- NMR- and those of the l3C-NMR spectrum correspond to 2 and to glucose. Enzymatic (P-glucosidase) and acidic hydro- lysis (1 N HC1/100 "C/3 h) led to glucose and to p-hydroxy- phenylethanol (tyrosol) (4)4), while basic hydrolysis of 1 for two h at 100 "C with 0.1 N NaOH produced salidrosid (5)", indicating the linkage of the three parts ofthe molecule. The as- signements of all the glucosyl signals in the 'H-NMR were additionally based on two-dimensional NMR studies (COSY experiments). 5 and 4 were identified by TLC with authentic samples. The chemical name of 1 is p-hydroxy-P-phenetyl-P- D-glucopyranoside 6-(5-ethyl-3-methoxycarbonyl)-4-pyri- dineacetate.

1 originated from Nuzhenide or LF (3)8 as well as 2 origi- nated from Ligstrosid, are important intermediates of 3: fur- ther treatment of l or 2 with 5 % H,S04 and subsequently with NH, results in formation of 3. Therefore, the constitu- tion of the pyridine ring seems to be the first step on the way from secoiridoid glucosides to 3. Depending on time and aci- dity, the following steps would probably be hydrolysis and then decarboxylation of the p, y unsaturated acid?

I thank Dr. H.-W. Fehlhaber, Hoechst A.G., Frankfurt/M., for kindly recording FAB-MS spectra and Dr. Ph. Fresenius, Karlsruhe, for his as- sistance with regard to nomenclature. The support of Fonds der Chemi- schen Industrie, FrankfudM., is gratefully acknowledged.

Experimental Part

IR-spectra: HITACHI 270-30 Infrared Spectrophotometer (270-30 Data Processor). 'H-NMR- and I3C-NMR-Spectra: BRUKER AM 300 WB

ZU (PR- 1"Graphic Printer"). - Optical rotation: PERKIN ELMER Po- larimeter 141. - Preparative column chromatography: silica gel KG 60 (MERCK) 70-230 mesh; solvent system A: toluene - EtOH (95:5), B: to-

(TMS). - FAB-MS: KRATOS MS 902 S. - UV: UV-VIS 240 SHIMAD-

Arch. Pharm. (Weinheim) 321,357-3.58 (1988) @ VCH Verlagsgesellschaft mbH, 0-6940 Weinheim, 1988 0365-6233 /88/0606-03.5 7 $OZ.SO/O

358 Willems

luene - EtOH (90:lO). - TLC: EtOAc - EtOH 70 % (80:20). Detection: 254 nm, Komarowsky-reagent7). The plant material was collected in September-October (1982-86) in outskirts of Frankfurt/Main.

Isolation procedure

Dried, powdered, ripe fruits extracted as described2), afforded a dark brown semi solid with an aromatic odour. Rough separation by prep. co- lumn chromatography using solvent system A and purification by column chromatography using solvent system B yielded LA 9. LA 9 crystallized from EtOAc-MeOH; - UV (MeOH): ?-,,,(log E) = 223

6 (ppm) = 1.08 (t, J = 7.5 Hz, 3H, -CH,-CHJ, 2.66 (q, J = 7.5 Hz, 2H, -CH,-CH,),2.72(t,J=6.6Hz,2H,CH2-2”),2.95(dt,J=7.7 and8.8Hz, 1TH-2’) partly overlapping with 3.03 (dt, J = 8.3 and 8.7 Hz, lH, H-4‘) 3.17 (dt, J = 8.7 and 8.8 Hz, IH, H-3’), 3.32 (dt, J = 7.2 and 8.3 Hz, I H, H-5‘) 3.57 (dt ,J= 6.6 and 7.7, IH, H-3b”), 3.75 (t, J = 7.7, lH, H-3,”) partly overlapping with 3.8 (s, 3H, -OCH,), 3.98 (dd, J = 7.2 und 11.1,

(4.31), 275 (3.85). - [ U I ~ -0.1’ (C = 1.0 EtOH). - ‘H-NMR (DMSO):

IH, H-6,’), 4.01 (s, 2H, CH,), 4.17 (d, J = 7.7, H-l’), 4.38 (d, J = 11.1, lH, H-6t,’), 5.06 (d, J = 4.4, IH, OH-3’), 5.08 (d,J= 4.7, IH, OH-2‘), 5.16(d,J=5.4, lH,OH-4’),6.67(d,J=6.8,2H,H-5’’andH-7”),7.03(d, J=8.4,2H,H-4“andH-8”),8.56(~, lH,H-6),8.78(~, IH,H-2),9.17(~,

lH, OH-6”). - 13C-NMR (DMSO): 6 (ppm) = 15.1 (CH,), 23.1 (CHJ, 34.3 (C-2”), 35.0 (CH,), 52.4 (OCH,), 64.6 (C-6’), 70.2 (C-I”), 70.2 (C- 4’), 73.4 (C-2‘*), 73.8 (C-5’*), 76.6 (C-3’*), 103.0 (C-l‘), 115.2 (C-5”, C-7’0, 126.1 (C-3), 128.7 (C-3”), 129.9 (C-4”, C-8”), 139.1 (C-5), 142.0 (C-4), 148.7 (C-2), 153.2 (C-6), 155.9 (C-6“), 166.5 (C=O), 169.9 (C=O), * = interchangeable. C,JH3,N0,, (505.5) calc. C 59.4 H 6.13 N 2.77 found C 59.1 H 6.20 N 2.79.

References

I M. Willems, Acta Agron. Acad. Sci. Hung. Supplementum 34, 66 (1985); Partly reported at the 33rd Annual Congress of the Society for Medicinal Plant Research 23-28 Sept. 1985 in Regensburg.

2 M. Willems, Arch. Pharm. (Weinheim) 320, 1245 (1987). 3 M. Willems, Arch. Pharm. (Weinheim), PH 396. 4 W. L. C. Veer, P. J. Oud and J . E. Ribbers, Rec. Trav. Chim. Pays-Bas

5 H. Thieme, Naturwissenschaften 51, 360 (1964). 6 P. Sykes, Reaktionsmechanismen der Organischen Chemie, 7. Aufl.,

S. 324, Verlag Chemie, Weinheim 1976. 7 P. J . Stevens, J. Chromatog. 14 , 269 (1964). [Ph 4201

76, 810 (1957).

Arch. Pharm. (Weinheim) 321,357-358 (1988)