Two phenethyl alcohol glycosides from Scutellaria orientalis subsp. Pinnatifida

Phytochemistry, Vol. 32, No. 6, pp. 1621-1623, Printed in Great Britain.

1993 0

003 l-9422/93 $6.00 + 0.00 1993 Pergamon Press Ltd

TWO PHENETHYL ALCOHOL GLYCOSIDES FROM SCUTELLARIA ORIENTALIS SUBSP. PINNATIFIDA iHSAN CALLS,* iCLAL SARACO~LU, A. AHMET BASARAN, OTTO STLcHEgt Hacettepc University, Faculty of Pharmacy, Department of Pharmacognosy, TR-06100 Ankara, Turkey; tSwiss Federal Institute of Technology (ETH) Zurich, Department of Pharmacy, CH-8092 Zurich, Switzerland (Received 9 July 1992) Key Word Index-Scutellaria

orientalis

subsp. pinnatijida;

Labiatae;

phenethyl

alcohol

glycosides;

darendosides A and B ( = deacyl martynoside).

Abstract- Two new phenethyl alcohol glycosides, darendoside A and B (= deacyl martynoside) were isolated from the methanolic extract of the aerial parts of Scutelluria orientalis subsp. pinnatijida, along with four known glycosides, syringin, martynoside, leucosceptoside A and verbascoside. On the basis of chemical and spectra1 evidence the structures of darendoside A and B were determined as /I-(4-hydroxyphenyljethyl O-/&D-apiofuranosyl-( 1-2)-O-j-Dglucopyranoside and S-(3-hydroxy-4-methoxypheny1)ethyl O-a-L-rhamnopyranosy1-(1+3)-0-/3-D-glucopyranoside ( = deacyl martynoside), respectively.

INTRODUCTION

During our systematic phytoehemical investigations on plants of the family Labiatae, we have studied Galeopsis Cl], Stachys [2, 31, Phlomis [4, 51, Leonurus [6], and Marrubium [7] species for their phenylpropanoid and

iridoid glycoside contents. We have now examined Scutellaria orientalis subsp. pinnatijida. This plant is used in folk medicine as an antidiarrheaic, haemostatic, tonic and for healing in western and central Anatolia. We now report the isolation and structural elucidation of two new phenethyl alcohol glycosides, darendoside A (1) and darendoside B (= deacyl martynoside) (2) as well as the four known glycosides, syringin (3), martynoside (4), leucosceptoside A (5) and verbascoside (= acteoside) (6). RESULTSAND DISCUSSION Compound 1 was obtained as an air-sensitive amorphous substance+ whose M, was confirmed as 432 by a FAB mass spectrum (m/z 433 [M+H]+, 455 [M+Na]+). Its IR spectrum contained absorption bands for hydroxyl (34OOcm-‘, br), and aromatic (1600, 1510cm-‘) functions. The ‘H NMR spectrum (see Experimental), exhibited characteristic signals arising from a p-substituted phenyl ethyl alcohol, AA’BB’ signals due to aromatic protons at 66.73 and 7.10 (each 2H, d, J= 8.4 Hz), and a benzylic methylene proton signal at 62.87 (2H, t, J = 7.8 Hz). Additionally, one doublet and one broad singlet methine signal, attributable to the anomeric protons of sugars, were observed at 64.38 (.7=7X Hz) and 5.42, respectively. All other resonances in ‘H and “CNMR *Author to whom correspondence should be addressed.

spectra supported the presence of /&D-glucose and S-Dapiose as sugar moieties (see Experimental). Acetylation of 1 yielded the heptaacetate la whose FAB mass spectrum exhibited a [M + H] + ion peak at m/z 727 and a [M +Na]+ at m/z 749 together with characteristic fragment ions resulting from cleavage of interglycosidic linkages: m/z 547 for hexa-O-acetyldiglycosyl [Api-Glc(OAc),] +, 289 for tri-0-acetylglucose CGlc(OAc),l + and 259 for terminal tri-0-acetylapiose [terminal Api (OAc),]’ . These data suggested that the sequence of sugars in 1 was apiosyl-glucose which was attached to p-hydroxyphenylethyl alcohol. The ‘H NMR spectrum of la revealed one aromatic (62.29) and six aliphatic acetyl (62.0-2.1) signals indicating the site of glycosidation of glucose unit to be the primary hydroxyl group but not the phenolic hydroxyl group of the phydroxyphenylethyl alcohol moiety. The complete interpretation of the ‘H NMR spectrum was based on a 2D‘H,‘H-homonuclear COSY experiment; no downfield shift upon acetylation for H-2’ (63.70, dd, J=7.7 and 9.5 Hz) of glucose was observed which indicated the site of glycosidation of the apiose unit on the glucose moiety. On the basis of these results the structure of 1 was determined as j?-(4-hydroxyphenyl)ethyl O-B-D-apiofuranosyl-(l+2)-O-B-D-ghtcopyranoside, for which we propose the trivial name darendoside A. The rare disaccharide moiety in 1, 2-O-/?-D-apiosyl-D-ghtcose, was previously reported by Bowden and Collins [S]. Compound 2 was also obtained as an air-sensitive amorphous compound. Its spectral data (UV, IR and tH NMR; see Experimental) were in good agreement with those reported for deacyl martynoside [ = /?-(3-hydroxy4-methoxyphenyl)ethyl 0-cr-L-rhamnopyranosyl-(l-r3)-0@glucopyranoside] [l]. TLC comparison of 2 with the

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Short Reports

OH

2 4 5 6

Rt

R2

H feruloyl

CHO CHS H H

foruloyl

cafteoyl

authentic sample also supported this assumption. However, deacyl martynoside was previously obtained by the alkaline hydrolysis of martynoside and isomartynoside Cl]; this is therefore the first report of the isolation of deacyl martynoside from nature. Therefore, we propose the trivial name darendoside B. Compound 3 was identified as syringin on the basis of spectral data (UV, IR, ‘H, 13C NMR and FAB mass spectra) which were in good agreement with those published [9, lo]. This is the first report of the isolation of syringin from a member of the family Labiatae. Compounds 4-6 were identified spectroscopically (UV, IR, ‘H NMR) as martynoside (4) [l], leucosceptoside A, (5) [l l] and verbascoside (6) [12]. EXPERIMENTAL General experimental procedures were as reported in ref. [4]. Plant material. Scutellaria orientalis L. subsp. pinnatijda Edmondson was collected from Malatya, Darende, Turkey in June 1990. A voucher specimen is deposited in the Herbarium of the Pharmacognosy Department, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey (HUEF 90-0019). Extraction and prepurijication. Air-dried aerial parts (600 g) were extracted with MeOH (2 1x 2) at 50”. The

combined extracts (45 g) were evapd. under vacuum nearly to dryness, H,O (250 ml) was added and the water insol. material removed by filtration. The filtrate was extracted with CHCI, (250 ml x 4), and the aq. phase coned and lyophilized to give a residue rich in crude glycosides (28 g). This material was dissolved in H,O and chromatographed over polyamide (200 g) eluting with H,O, following by increasing concns of MeOH to yield 5 frs, A (H20, 18.9g), B (25% MeOH, 0.44g), C (50% MeOH, 2.5 g), D (75% MeOH, 1.3 g) and E (MeOH, 4.8 g). Isolation of compounds l--6. A portion of fr. A (9.25 g) was chromatographed over silica gel eluting with EtOAc-MeOH-H,O (20:3.3:2.7) to give 5 frs Al-A5. Fr. A3 (325 mg) was subjected to MPLC (352 x 18 mm, packed with Sepralyte 40 pm) using gradient elution with MeOH in H,O (5-100% MeOH) and yielded two frs, A31 and A3-2. Fr. A3-1 (25 mg) rechromatographed over silica gel eluting with CHCl,-MeOH-H,O (40: 10: 1) to give 1 (10 mg). Fr. A3-2 (50 mg) was rich in compounds 2 and 3 and was rechromatographed over silica gel using the same solvent system used for 1 to yield 2 (5 mg) and 3 (22 mg). A portion of fr. C (1.27 g) was chromatographed over silica gel eluting with CHCI,-MeOH (9:1-+7: 3) to give 3 frs, Cl --C3. Fr. C2 contained compound 5 (25 mg). Fr. Cl (137 mg) was subjected to MPLC using gradient elution with MeOH in H,O (30-75%MeOH) to yield 4 (30 mg). Fr. C3 was subjected to Sephadex LH-20 CC using MeOH and yielded compound 6 (50 mg). Darendoside A (1). FAB-MS m/z 433 [M+H]+, 455 [M + Na]‘, (talc. for C,9H,,0, ,: h4, (432.4). UVni:F” nm: 214,224,276 and 285. IR vi:: cm-‘: 3400, 1600 and 1510. ‘HNMR (300 MHz, CD,OD): aglycone moiety 66.73(2H,d,.l=8.4Hz,H-2andH-6),7.10(2H,d,J= 8.4 Hz, H-3 and H-5), 4.06 and 3.64-3.75 (IH each, signal patterns unclear due to overlapping, H-r); 2.87 (2H, t. J = 7.4 Hz, H-P), glucose moiety: 64.38 (1H, d, J = 7.8 Hz, H-l’), 3.40 (lH, dd, 3=7.89/9.0 Hz, H-2’), 3.50 (lH, d, J =9.0 Hz, H-3’), 3.32 (lH, t, J=9.0 Hz, H-4’), 3.27-3.35 (lH, signal patterns unclear due to overlapping, H-5’), 3.89 (lH, dd, 5=12.0/2.0 Hz, H&‘b), 3.69 (lH, dd, J = 12.0/5.0 Hz, H-6,‘a), apiose moiety: 65.42 (lH, hr s, Hl”), 3.97 (lH, br s, H-2”) 4.02, 3.73 (2H, d, J,,= 9.7 Hz, H,-4”), 3.64 (2H, br s, H,-5”). 13CNMR (75.5 MHz, CD,OD): aglycone moiety: 6 130.8 (C-l), 130.9 (C-2). 116.1 (C-3),156.8 (C-4), 116.1 (C-5), 130.9 (C-6), 72.0 t (Ca), 3 1.1 t (C-p), glucose moiety: 6 103.3 d (C- 1’). 78.4 d (C2’), 78.3 d C-3’), 71.7 d (C-4’), 77.8 d (C-5’), 62.7 t (C-6’), apiose moiety: 6 110.5 d (C-l”), 78.0 d (C-2”), 80.7 s (C-3”), 75.4 t (C-4”), 66.2 t (C-5”). Acetylation. Treatment of 1 (5 mg) with Ac,O (0.3 ml) and pyridine (0.3 ml) at room temp. overnight, followed by CC over silica gel using C,H,-Me&O (9: 1) gave darendoside A heptaacetate (la). Darendoside A heptaacetate (la). FAB-MS m/z: 727 [M 547 [Glc-Api(OAc),] +, 289 +, 749 [M+Na]+ (talc. for &zOAc),l+, 259 [terkinal Api(OAc),]+. C33H42018: 726.68). IR vz; cm -I: 2900, 1725, 1600, 1510, 1350, 1210. ‘H NMR (300 MHz, CDCI,): aglycone moiety 67.0 (2H, d. J= 8.4 Hz, H-2 and H-6), 7.24 (2H, d,

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Short Reports J=8.4 Hz, H-3 and H-5), 4.06/3.73 (each lH, m, HZ-r), 2.95 (2H, t,J=7.5 Hz, H,$),glucose moiety: 64.43 (lH,d, J=7.7 Hz, H-l’), 3.70 (lH, dd, J=9.5/7.7 Hz, H-2’), 5.17 (lH, t, J =9.4 Hz, H-3’), 4.97 (lH, t, J =9.7 Hz, H-4’), 3.65 (lH, m, H-5’), 4.10 (2H, dd, J=12.0/2.2 Hz, H-6’a), 4.23 (2H, dd, J = 12.0/4.8 Hz, H-6’b), apiose moiety: 6 5.11 (1H, br s, H-l”), 5.17 (lH, br s, H-2”), 4.28,4.07 (AB system, J,, = 10.3, H&“), 4.62 (2H, br s, HZ-S’), 2.29 (3H, s, arom. OAc), 2.00, 2.02, 2.06, 2.07, 2.08, 2.10 (each 3H, s, aliph. OAc). Darendoside B (=deacyl martynoside) (2). UV $EF’” nm: 216,233,264 and 286. IR vi:: cm-‘: 3400,160O and 1510. ‘HNMR (300 MHz, CD,OD): aglycone moiety 66.73(1H,d,J=8.2Hz,H-5),6.70(1H,dd,J =8.2/1.2Hz, H-6), 3.40-4.10 (2H, m, H-r), 2.85 (2H, t, J = 6.7 Hz, H-/3), 3.85 (3H, s, OMe), glucose moiety: 64.33 (lH, d, J=7.5 Hz, H-l’), 3.40-4.10 (signal patterns unclear due to overlapping, H-2’, H-3’, H-4, H-5, H-6’), rhamnose moiety: 65.19 (lH, d, J= 1.5 Hz, H-l”), 3.4C4.10 (signal patterns unclear due to overlapping, H-2”, H-3”, H-4”, H5”), 1.28 (3H, d, J=6.0 Hz, H-6”). Syringin (3). UV, IR, FAB-MS, ‘H and 13CNMR (CD,OD) data were identical with those described in. c9, 101. Martynoside (4). ‘HNMR as reported in ref. Cl]. Leucosceptoside A (5). ‘H NMR as reported in ref. [ll]. Verbascoside (6). ‘H NMR as reported in ref. [12].

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