13C NMR studies on the structure of 5H- and 6H-indolo-[2,3-b]quinolines and the related compounds

Alkaloids from Tetrastigma hemsleyanum and Their Anti-Inflammatory Effects on LPS-Induced RAW264.7 Cells

Alkaloids 1–10 were isolated from the aerial parts of Tetrastigma hemsleyanum (APTH) and obtained from species of the genus Tetrastigma for the first time. The chemical structures of the isolated compounds were identified by NMR, UV, and MS analyses. Their anti-inflammatory activities were investigated by measuring nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. Among all the isolates, compounds 6, 7 and 10 showed potent inhibitory activity against LPS-stimulated NO production in RAW264.7 cells (IC₅₀: 31.9, 25.2 and 6.3 μM, respectively). Furthermore, APTH and S-(−)-trolline (10) inhibited induction of inflammatory cytokines or mediators such as interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) via suppression of nuclear factor κB (NF-κB) translocation into the nucleus. In addition, 10 suppressed extracellular signal-regulated protein kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) phosphorylation in a dose-dependent manner. These results conclusively demonstrated that compound 10 displays anti-inflammatory activity via suppression of NF-κB activation and the ERK-MAPK signaling pathway in LPS-stimulated RAW264.7 cells.

A new amino amidine derivative from the wood-decaying fungus Xylaria cf. cubensis SWUF08-86

The secondary metabolites of Xylaria cf. cubensis SWUF08-86 fungus were investigated, and the chromatographic separation of the crude extracts yielded seventeen compounds. The structure elucidation by spectroscopic analysis including 1D and 2D NMR and the comparison of these data with literature, along with HREIMS spectrometry, revealed one new amino amidine derivative (1), together with five known simple cyclic dipeptide analogs, diketopiperazines (2-6) and eleven other known compounds, including one hemi-cycline (10), three aromatic derivatives (11-13), one sesquiterpene (14) and three sterols (15-17). The isolated compounds were screened for anticancer and anti-pathogenic bacterial and fungal activities. Based on this work, Xylaria cf. cubensis SWUF08-86 has proven to be a diverse secondary metabolites producer.

Alkyl, aryl, alkylarylquinoline, and related alkaloids

The Rutaceae continues to be the primary source of new alkyl-, aryl-, and alkylarylquinolin/ones. In the past 17 years, the overall distribution of these alkaloid types within the family has changed little since the chemosystematics reviews by Waterman (270), Mester (40), and da Silva et al. (279). Alkylquinolones dominate the reported isolations with about 51% of the total, with arylquinolones (16%), alkylquinolines (15%), alkylarylquinolines (11%), arylquinolines (3%), alkylarylquinolones (2%), and quinolines (2%) as the significant structural groups contributing to the remainder of this class of alkaloids. The alkyl-, aryl-, and alkylarylquinolin/one alkaloids occur in 50 species belonging to 24 genera and 6 subfamilies. Despite the intensive chemical exploration of many species from other plants in the Rutales family, but not in the family Rutaceae, the first alkaloid alkylquinolone from a simaroubaceous plant (160) was not reported until 1997. Although many additional alkaloids have been reported, some of new structural types (Bo.4), substantial biosynthetic work on plant-derived alkylquinolin/ones has not yet been carried out. The biosynthesis of some of these alkaloids in bacteria was firmly established as being derived from anthranilic acid. Outside of the Rutales, alkyl-, aryl-, and alkylarylquinolin/ones have not been found, except for simple quinoline (A.1; only one) and 2-methylquinoline derivatives in the Zygophyllaceae, and only an atypical quinolone derivative (Ao.1) in the Asteraceae family. A few 3-phenylquinolines (2), 3-(1H-indol-3-yl)quinoline (1), and quinoline-quinazoline (1) alkaloids have been reported from only a single genus in the Zygophyllaceae. Tryptophan-derived quinolines in higher plants are confined to a few 2-carboxylicquinolin/ones (6) and 4-carbaldehydequinolines (5); the former found in the Ephedraceae (5), Boraginaceae (1), Fagaceae (1), Ginkgoaceae (1), Plumbaginaceae (1), Solanaceae (1), and Apiaceae (1), and the latter in the Moraceae (3), Alliaceae (1), and Pontederiacae (1). The number of quinolones derived from glycine and a polyketide is also limited. 5-Alkyl-2-methylquinolin-4(1H)-ones (8) occur in the Euphorbiaceae, and 5-alkyaryl-2-methylquinolin-4(1H)-ones ((3) in the Sterculiaceae. Alkylquinolin/ones are well-known as typical alkaloids of three Proteobacteria and three Actinobacteria; the genus Pseudomonas yielded the majority (46%) of the total number of alkaloids reported (39). 2-Carboxylicquinolin/ones (4) and 4-carbaldehydequinolines (6) are minor constituents in both divisions of bacteria. More interesting are the quinolactacins (7), in which the second nitrogen is derived from L-valine or L-isoleucine, recently reported to occur only in the fungus Penicillium. Many of these diverse alkaloids have served directly as medicines or as lead compounds for the synthesis (258) of derivatives with an improved biological profile. It is apparent from the summary view of the alkyl-, aryl-, and alkylarylquinolin/ones reported in the Rutaceae that they help to confirm the affinity between Rutoideae tribes and provide firm support for placing the Spathelioideae and the Dictyolomatoideae close to the more primitive Zanthoxyleae tribe. On the other hand, the bacteria and fungi are needed for more substantial chemical studies. When more data become available, it is likely that useful systematic correlations will emerge. More detailed studies regarding the biosynthetic pathways of the alkyl-, aryl-, and alkylarylquinolin/ones in the Rutaceae and in bacteria are needed. Such studies would clarify the differences in the pathways based on their derivation from anthranilic acid in bacteria and in rutaceous plants. Finally, this survey indicates that the Rutaceae, and various bacterial and fungal species offer considerable potential for the discovery of new or known alkaloids with significant and possibly valuable biological activities.