Chemical Constituents of the Liverwort Preiss/A Quadrata (Scop.) Nees

J. Hattori Bot. Lab. No. 81: 243-247 (Feb. 1997)

CHEMICAL CONSTITUENTS OF THE LIVERWORT PREISS/A QUADRATA (SCOP.) NEES

1 1 YOSHINORI ASAKAWA , TOSHIHIRO HASHIMOT0 , KYOKO AKAZAWA1 and SIEGFRIED HUNECK2

ABSTRACT. The ether and methanol extract of Preissia quadrata (Scop.) Nees contained not only various sesquiterpenes but also two cyclic bis(bibenzyls), riccardin Band neomarchantin A. The terpenoids and bis(bibenzyl) constituents found in the present species are not closely related to those of Conocephalum, but to some Marchantia species.

INTRODUCTION The thalloid liverworts produce various lipophilic terpenoids and macrocyclic bis (bibenzyls) some of which show interesting biological activity including muscle relax ants (Asakawa, 1993; Taira et al. 1994), 5-lipoxygenase and calmodulin inhibitory activity (Asakawa 1990a, b, 1993, 1995ab; Schwartner et al. 1995). Preissia quadrata, belonging to the Marchantiaceae, has been investigated chemi cally and a number of ftavonoids (Campbell et al. 1979) and two bibenzyls, lunularic acid (1) and lunularin (2) (Huneck 1975; Gorham 1977) have been identified. On the basis of fiavonoid constitution, it has been suggested that the Preissia closely related to Conocephalum (Campbell et al. 1979). We are continuing to study the chemical constituents of liverworts from view point of their biological activity and chemosyst ematics (Asakawa 1982, 1995b). We have investigated the volatile and hydrophilic components of European P. quadrata. Here we report the distribution of sesquiterpe noids and macrocyclic bis(bibenzyls) in P. quadrata as well as chemosystematic discussion of this species.

EXPERIMENTAL Plant material Preissia quadrata (Scop.) Nees was collected in Germany, August, 1992 and identified by S. H. and deposited at Faculty of Pharmaceutical Sciences, Tokushima Bunri University. Extraction and isolation Preissia quadrata was extracted with ether for 2 weeks and then with methanol for 2 weeks. Both extracts were filtered and combined and the solvent evaporated to give green oil (l.554g) which was analyzed directly by TLC, GC and GC-MS. TLC was

1 Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770, Japan. 2 Institute for Plant Biochemistry, Wienberg 3, Halle/Saale, D0-4050, Germany: Present Address: Fliederwerg 34a, D-06179 Langenbogen/Saalkrs. Germany. 244 J. Hattori Bot. Lab. No. 81 I 9 9 7

carried out on precoated plates (Kieselgel 60 F 254, 0.25 mm thick, Merk) using n-hexane-ethyl acetate ( 4 : 1) and spots were detected by illumination with an UV lamp or by spraying 30% HiS04, followed by heating at l l0°C. The GC-MS analysis of the crude extract and each fraction (see later) was carried out using Hewlett-Packard 5890 Series II gas chromatograph coupled with mass selective detector (MSD 5971A) at 70 eV and on a fused silica column coated with DB-17 (30m X0.25 mm i.d., film thickness 0.25 mm) using helium as the carrier gas ( 1 ml/min). The temperature programming was performed from 50°C isothermal for 3 min, then 50-250°C at 5°C/min, and finally isothermal at 250°C for 15 min. Injection temperature was 250°C. GC-MS analysis showed the presence of o-elemene (6), ,8-caryophyllene (7), cuparene (8) and germa crene-D (9) of which o-elemene was the major component. The remaining green oil ( 1.524 g) was chromatographed on Sephadex LH-20 using methanol and chloroform (1: 1) as the solvent to give six fractions: fr. A (326mg), fr. B (452mg), fr. C (218 mg), fr. D (160mg), fr. E (237mg) and fr. F (95.4mg). Fr. E was rechromato graphed on silica gel to give 43 fractions. From Fr. E-22- 25, a cyclic bis(bibenzyl) (65 mg) was obtained. Its spectral data were identical to those of riccardin B (3) (Asakawa 1995b). From the fr. E-26- 27, the second macrocyclic bis(bibenzyl) (5.2 mg) was obtained and the spectral data of which were in accordance with those of neomarchantin A (4) (Asakawa 1995b). Fr. C and Fr. D were combined and the mixture was chromatographed on silica gel using n-hexane and ethyl acetate gradient to give 68 fractions. Fr. C-D-1 contained a mixture of sesquiterpenoids including bicyclogermacrene (S) (6.4mg) (Asakawa 1982, 1995b). Fr. C-D-2 (12.6mg) was purified by column chromatography using the same solvent to give ( - ) bicyclogermacrene (12.6mg). Frs. C-D-51- 52 contained stigmasterol (17.6mg). Fr. C-D-6 (12.6mg) was analyzed by GC-MS to detect the presence of sesquiterpene hydrocarbons, ,8-elemene (6), ,8-caryophyllene (7), germacrene-D (9), a-copaene (10), ,8-barbatene (11) and germacrene-B (12). This fraction contained four unidentified sesquiterpene hydrocarbons ([M] + 204 (base peaks: 91, 91, 161and121, respectively) as minor components.

RESULTS AND DISCUSSION A mixture of ether and methanol extracts of P. quadrata was chromatographed on Sephadex LH-20 to give a mixture of sesquiterpenoids in which 8 sesquiterpene hydrocarbons (S- 12) were identified. These sesquiterpenoids are very frequent not only in the Jungermanniales but also in the Metzgeriales and the Marchantiales (Asakawa 1982, 1995b). Two cyclic bis(bibenzyls), riccardin B (3) and neo marchantin A ( 4) were obtained from the polar fractions of P. quadrata. The former compound and its related cyclic bis(bibenzyl) derivatives have been isolated from Riccardia multifida and several Marchantia species and the latter one from the leafy liverwort, Schistochila glaucescens from New Zealand (Asakawa 1995b). This is the first example of the isolation of neomarchantin A from a thalloid liverwort. Campbell et al. ( 1979) reported that the genus Preissia was closely related to Conocephalum on the basis of ftavonoid chemistry. However, C. conicum, for example, does not contain Y. AsAKAWA et al. : Chemical constituents of the liverwort Preissia quadrata 245

(1) Lunularic acid ; R=C02H (2) Lunularin ; R=H

(3)Riccardin B

HO (5) ent-Bicyclogermacrene (6) 8-Elemene

(4) Neomarchantin A

(7) ~-Caryophyllene (8) Cuparene (9) Germacrene-D

(10) o:-Copaene (11) ~-Barbatene (12) Germacrene-B 246 J. Hattori Bot. Lab. No. 81 I 9 9 7

any of the cyclic bis(bibenzyls) which have been isolated from P. quadrata. C. conicum and C. japonicum also biosynthesize mono- and sesquiterpenoids as well as (R )-( + )-1- octen-3-yl acetate, in relatively high amounts (Asakawa 1980; Toyota & Asakawa . 1993), but no monoterpenoid has been detected in P. quadrata. Thus, P. quadrata differs from the Conocephalum species on the basis of terpenoid and cyclic bis (bibenzyl) constituents. P. quadrata shows chemical similarities to the Marchantia species, such as M. paleacea var. diptera, M. palmata and M. polymorpha because they produce not only bis(bibenzyl) but also sesquiterpenoids identical or very similar to those isolated from or detected in P. quadrata.

Note: After this paper was accepted for the publication in J. Hattori Bot. Lab. on 29 June 1996, Konig et al. reported the presence of the sesquiterpene hydrocarbons (5, 7, 9, 10 and 12) in P. quadrata (Konig, W. A., N. Btilow, C. Fricks, S. Melching, A. Rieck and H. Muhle. 1996. The sesquiterpene constituents of the liverwort Preissia quadrata. Phytochemistry 43: 629- 633).

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