nan Suciati

Secondary metabolites of the sponge-derived fungus Acremonium persicinum.

This study reports the isolation and characterization of six new acremine metabolites, 5-chloroacremine A (4), 5-chloroacremine H (5), and acremines O (6), P (7), Q (8), and R (9), together with the known acremines A (1), F (2), and N (3) from the fungus Acremonium persicinum cultured from the marine sponge Anomoianthella rubra. The relative configuration of acremine F (2) was determined by analyses of proton coupling constant values and NOESY data, and the absolute configuration confirmed as (1S, 4S, 6R) by X-ray crystallographic analysis of the borate ester derivative 15. Acremines O, P, and R were each shown to be of 8R configuration by ¹H NMR analyses of MPA esters. The relative configurations suggested for acremines P and Q were each deduced by molecular modeling together with NOESY and coupling constant data. The ³J(H-C) values in acremine P were measured using the pulse sequence EXSIDE, and the observed ³J(H8-C4) of 5.4 Hz and small ³J(H-C) values (<1.5 Hz) from H-8 to C-10 and C-11 were fully consistent with stereoisomer 7a. For acremine Q, NOESY data combined with molecular modeling established the preferred diastereomer 8a.

Structures and Anatomical Distribution of Oxygenated Diterpenes in the Australian Nudibranch Chromodoris reticulata

The structures and stereochemistry of six new diterpenes (1–6), two of which contain cyclic imine functionality, have been deduced by 2D NMR spectroscopy. The anatomical distribution of these, and of 17 other diterpenes (7–23) that were also isolated, has been investigated. The known compound aplyroseol-2 (14) was the major compound in the mantle tissue along with some dialdehydes, while the linear furan ambliofuran (7) was the only diterpene found solely in the internal organs. The presence of lactone-acetal-hemiacetal functionality in many of the isolated compounds is a consequence of the reactive dialdehydes present in the mollusc.

Phytochemical Study of Fagraea spp. Uncovers a New Terpene Alkaloid with Anti-Inflammatory Properties1

Phytochemical investigation of the stem bark of F. racemosa JACK ex WALL (Loganiaceae) from East Java, Indonesia, has resulted in the isolation of a new alkaloid fagraeoside along with the iridoid glycoside secologanoside. Fagraeoside may be derived from the condensation of secologanin with L-asparagine, and represents a rare example of a terpene alkaloid in which the amino acid component is non-aromatic. Investigation of three additional species of Fagraea provided known lignans, iridoid or secoiridoid glycosides, and flavanol-6-C-glucosides, thus it is likely that iridoid and secoiridoid glucosides are chemotaxonomic markers for the Fagraea genus. Fagraeoside inhibited the production of prostaglandin E2 in 3T3 murine fibroblasts (IC50 ~5.1 µM), and was not cytotoxic to this cell line or to a P388 murine leukaemia cell line. Selected isolated compounds, including fagraeoside, showed low to moderate activity in anti-acetylcholinesterase screening.

Chemoecological studies on marine natural products: terpene chemistry from marine mollusks

Abstract Some species of nudibranchs (Mollusca) protect themselves from predatory attacks by storing defensive terpene chemicals acquired from dietary sponges (Porifera) in specialized body parts called MDFs (mantle dermal formations), often advertising their unpalatability to potential predators by means of bright coloration patterns. Consequently, the survival of these trophic specialist species is closely related to the possibility of obtaining the defensive tools from sponges that live in their immediate vicinity; therefore, it is important to determine as precisely as possible the chemical composition of nudibranch extracts prior to any ecological studies addressing issues that involve their alimentary behavior and their defensive strategies, including the significance of their color patterns. Some of our recent studies on the chemical composition of terpene extracts from nudibranchs belonging to the genera Chromodoris and Hypselodoris are summarized. We also report the development of a method to assay extracts and purified metabolites for their feeding deterrent activity against co-occurring generalist predators. In a recent chemoecological study, showing that repugnant terpene chemicals are accumulated at extremely high concentrations in exposed parts of the nudibranchs’ bodies, the feeding deterrence assays were carried out on the generalist marine shrimp Palaemon elegans, very common in the Mediterranean. We have modified this assay for use with the Australian shrimp species P. serenus, and confirmed the ecological validity of the assay by analysis of extracts from species of sponges and mollusks that live in the same habitat as P. serenus. The deterrent properties of haliclonacyclamine alkaloids isolated from the sponge Haliclona sp. were demonstrated, with the alkaloid mixture demonstrating palatability deterrence at concentrations as low as 0.05 mg/mL, and complete deterrence at 0.75 mg/mL. In contrast, the diterpene thuridillin metabolites from the sacoglossan mollusk Thuridilla splendens did not deter feeding by P. serenus.

Revision of the structure of acremine P from a marine-derived strain of Acremonium persicinum

The previously published structure of the fungal metabolite acremine P is revised by re-evaluation of chemical shift values and NOESY data, and by DFT calculations.

New Apicidins and a Polyketide from the Fungus

Chemical investigation of the culture of Fusarium semitectum isolated from a dead cicada skin collected in Indonesia has yielded three new tetrapeptides, namely apicidins E-G (1 – 3) together with the new polyketide 4 and six known compounds. The structures of the new metabolites were deduced by NMR and mass spectrometry, while the structure of polyketide 4, possessing an unusual eight-membered ring, was further confirmed by methylation to the methoxy derivative 5. Based on the result of this study together with earlier reports from the literature, we can suggest that tetrapeptide apicidin and its congeners are possibly chemotaxonomic markers of this fungal species.