Chemical Constituents of Malagasy Liverworts, Part III: Sesquiterpenoids from Bazzania decrescens and Bazzania madagassa

Abstract

The genus Bazzania is one of the most phytochemically studied among the liverworts and has been shown to produce a wide range of sesquiterpenoids and aromatic compounds. The sesquiterpenoids that have been detected are of the aromadendrane, bicyclogermacrene, bazzanene, barbatene, calamenane, cuparane, chamigrene, drimane, pinguisane, myltaylane, and cyclomyltaylane types.1,2) Lignans and bisbibenzyls were also isolated from Bazzania trilobata.3,4) Interestingly, sesquiterpene caffeates, which have been shown to have useful activities such as cytotoxic, antimicrobial, antifungal, and superoxide anion release inhibitory activity have only been found in Bazzania species. 1,2,5) In the course of our ongoing phytochemical studies of the Malagasy liverworts, 6,7) six compounds including a new cuparane-type sesquiterpene (1) were isolated from Bazzania decrescens, while Bazzania madagassa produced a new cyclomyltaylane-type sesquiterpenoid (2) and a new acoradienol: 1S*,4S*,5S*, acora-8(15),9-dien-7R*-ol (3). The biogenesis of the cyclomyltaylane-type sesquiterpenoid is discussed. Results and DiscussionBazzania Decrescens The ether extract of B. decrescens was analyzed with GC/MS and shown to contain a-barbatene (1.7%), cuparene (6%), and bazzanene (41.6%). Silica gel column chromatography of the remaining extract afforded five fractions. Purification on Sephadex LH-20, silica gel, and preparative HPLC of each fraction yielded isobicyclogermacrenal, 8) drimenol and a mixture of drimenyl cis and trans caffeate, 9) which was converted to the trans form on standing at room temperature overnight, 2-methoxy-5-hydroxycuparene (HM-1), 10) and friedelin together with a new cuparane-type sesquiterpenoid (1) (Fig. 1). The structures of the known compounds were determined by comparison of their spectral data with those of authentic samples and reported in the literature.Compound 1 exhibited the molecular formula of C 16 H 24 O 2 as determined using HR-EI-MS. Its IR spectrum showed absorption bands for an hydroxyl group (3328 cm Ϫ1) and aromatic methine strech (3086 cm Ϫ1 ), while the UV spectrum displayed an aromatic ring (206, 272 nm). The 1 H-NMR spectral data (Table 1) , and an upfield methyl signal at d 7.7. The positions of the hydroxyl group at C-2, methyl group at C-3, and methoxyl group at C-4 were determined by careful interpretation of the HMBC spectrum (Fig. 2). Thus the structure of 1 was determined to be 2-hydroxy-4-methoxy-cuparene.Compound HM-1 (4) was previously isolated from the phytopathogenic fungus Helicobasidium mompa, 10) but has not been found in liverworts of the Bazzania genus even though they are known to contain cuparane-type sesquiterpenes as chemical markers. 1)Bazzania Madagassa GC/MS analysis of the ether extract of B. madagassa revealed b-barbatene (5.8%), isobazzanene (9.2%), chamigrene (6.8%), d-cuparene (16.2%), and acora-3,5 diene (1.3%). A combination of column chromatography on Sephadex LH-20, silica gel, and ODS RP-18 of the remaining extract yielded two new compounds (2, 3).Compound 2 exh...

Chemical constituents of Malagasy liverworts: Cyclomyltaylanoids from Bazzania madagassa

“…The NMR spectra, CD spectral data, and the optical rotation of 1 were identical to the previously isolated compound from the liverwort sample 2003LIV5. The absolute configuration was determined by the observation of the negative Cotton effect (De 298 À 12) in the CD spectrum as determined previously (Asakawa et al, 1991) and the R configuration of C-1 and C-5 was substantiated by NOESY correlations between H-5 and H-8b and between C-1 acetyl methyl and C-14 and C-7 methyl groups (Harinantenaina et al, 2005). This time 1 was obtained in crystalline form (from 1:1 MeOH/Et 2 O) and its structure was confirmed by X-ray analysis.…”

“…The isolation of structurally and biologically interesting terpenoids and aromatic compounds from liverworts incited us to investigate the chemical constituents of hepatics growing widely in Madagascar, which has very rich flora (Asakawa, 1995(Asakawa, , 2004Harinantenaina and Asakawa, 2004a,b;Harinantenaina et al, 2005). Bazzania madagassa is a leafy liverwort widely growing in the Eastern part of Madagascar and is often found at the base of trees or on rotten logs.…”

“…This group of compounds has been detected in the genus Bazzania although the latter do not have any morphological affinity with Mylia (Asakawa et al, 1991;Wu and Chang, 1992). The isolation of a new cyclomyltaylane sesquiterpenoid (1) and 1S * ,4S * ,5S * , acora-8(15),9-dien-7R * -ol from B. madagassa collected in Moramanga/Andasibe-Madagascar (voucher number: 2003LIV5) prompted us to investigate a larger amount of sample collected in Moramanga/Lakato (2003LIV3) (Harinantenaina et al, 2005). Five new cyclomyltaylanoids (2-6), together with 1R,5R-diacetoxycyclomyltaylan-10-one (1), (+)-globulol (Toyota et al, 1999), and ent-4b,10a-dihydroxyaromadendrane (Nagashima et al, 1994) were isolated.…”

Chemical Constituents of Malagasy Liverworts, Part V: Prenyl Bibenzyls and Clerodane Diterpenoids with Nitric Oxide Inhibitory Activity from Radula appressa and Thysananthus spathulistipus

“…As part of our ongoing systematic investigation of the chemical constituents of Malagasy liverworts, [2][3][4][5] Thysananthus spathulistipus (Lejeuneaceae) and Radula appressa (Radulaceae) have been studied. Radula species have been extensively investigated 6,7) while only a few publications are available on species in the genus Thysananthus.…”

“…1,[6][7][8] The present paper deals with the isolation and structural determination of two clerodane diterpenes (1, 2), prenylated bibenzyls, and their rearranged products (3)(4)(5)(6)(7)(8) from T. spathulistipus and R. appressa, respectively, as well as their nitric oxide (NO)-inhibitory properties in lipopolysaccharide (LPS)-induced RAW 264.7 cells. To the best of our knowledge, this is the first report on the phytochemical investigation of the two liverwort species.…”