New Bisindole Alkaloids Isolated from Myxomycetes Arcyria cinerea and Lycogala epidendrum
Kazuaki Kamata, Makiko Kiyota, Ayano Naoe, Satomi Nakatani, Yukinori Yamamoto, Masahiko Hayashi, Kanki Komiyama, Takao Yamori, Masami Ishibashi
Chemical and pharmaceutical bulletin
The myxomycetes (true slime molds) are an unusual group of primitive organisms that may be assigned to one of the lowest classes of eukaryotes. 1) During our studies on search for bioactive natural products from myxomycetes, 2-4) we recently investigated a field-collected sample of fruit bodies of Arcyria cinerea and Lycogala epidendrum collected at Kochi prefecture. Here we describe isolation and structure elucidation of new bisindole alkaloids (1-5) along with seven known bisindoles (6-12),
... d their cytotoxic activity. Particularly, compound 12 was found to be cytotoxic against a panel of 39 human cancer cell lines. Results and Discussion The wild fruit bodies of Arcyria cinerea, collected in Kochi Prefecture, Japan, were extracted with 90% MeOH and 90% acetone. The combined extracts were separated by chromatographies on silica gel, ODS, and Sephadex LH-20 to give two new bisindole alkaloids, named cinereapyrrole A (1) and B (2), together with a known compound, arcyriarubin A (6), which was previously isolated from Arcyria denudata, 5) and Lycogala epedindrum. 6) Cinereapyrrole A (1) was shown to have the molecular formula C 22 H 17 N 3 O 4 by the HR-FAB-MS data (m/z 387.1208, [M ϩ ], D Ϫ1.1 mmu). The UV spectrum of 1 showed absorption maximum at 283 nm, indicating the presence of conjugated system(s), while the IR absorption bands observed at 3396 and 1695 cm Ϫ1 implied the presence of hydroxy and conjugated carbonyl groups. The 1 H-NMR spectrum of 1 in CD 3 OD (Table 1 ) showed ten signals for nine aromatic protons and one methoxy group. The analysis of the 13 C-NMR (Table 2 ) and HMQC spectra of 1 clarified the presence of twenty two carbons including nine sp 2 methines, eleven sp 2 quaternary carbons, one methoxy (d C 51.3), and one carboxy or carboxy ester carbon (d C 163.6). By analysis of the 1 H-1 H COSY and HMBC spectra of compound 1 suggested the presence of two sets of 5-hydroxyindole moieties by observation of the following cross peaks Two new bisindole alkaloids, named cinereapyrrole A (1) and B (2), were isolated from wild fruit bodies of Arcyria cinerea and three new bisindole alkaloids (3-5) were isolated from wild fruit bodies of Lycogala epidendrum. Seven known bisindoles (6-12) were concomitantly obtained from them. The structures of the new compounds were elucidated by spectral data. Among these bisindole alkaloids, compound 12 showed cytotoxicity against cultured tumor cell lines.