J. Jantina Kettenes-van den Bosch

RP-hPLC/ESI MS determination of acyl chain positions in phospholipids

Since phospholipids are used as excipients in many pharmaceutical products, there is a need for validated strategies to characterize the phospholipid constituents. We describe a reversed phase HPLC/electrospray ionization mass spectrometry method that is an alternative to the laborious phospholipase A2 treatment commonly used to determine the acyl chain positions in phospholipids. This reversed phase HPLC/electrospray mass spectrometry system (a) shows good chromatographic resolution for phosphatidylcholine molecular species, (b) allows determination of the composition of complex mixtures of phosphatidylcholines, and, most important, (c) allows unequivocal assignment of the positions of the acyl chains on the glycerol backbone in mixtures of POPC and OPPC and in mixtures of POPE and OPPE.

Metal binding of Lissoclinum patella metabolites. Part 1: Patellamides A, C and ulithiacyclamide A

Abstract Studies on three Thz, and Oxn containing cyclic peptides, patellamide A and C (1, 3) and ulithiacyclamide A (9) isolated from the Indo-Pacific ascidian (seasquirt) Lissoclinum patella have delineated their metal binding selectivity. Patellamide C (3) shows extreme selectivity for Cu2+ even in the presence of an excess of Zn2+ and shows no binding at all to Co2+, Ni2+ and Hg2+. Patellamide A (1) is less selective for Cu2+, whereas ulithiacyclamide A (9) shows selectivity similar to that of patellamide C (3). The selectivity was studied by circular dichroism spectroscopy and mass spectrometry. The CD spectra obtained whilst patellamide C was slowly titrated with Cu2+ show one isosbestic point indicating the Cu2+ binding involves only two conformations. These studies indicate that Cu2+, not Zn2+ is the biologically relevant metal for these compounds and point towards a potential ecological function of these complexes.

Axinellin C, a proline-rich cyclic octapeptide isolated from the Fijian marine sponge Stylotella aurantium

The structure of a new cyclic octapeptide, axinellin C, (cyclo[Thr1-Val2-Pro3-Trp4-Pro5-Phe6-Pro7-Leu8]), with all-trans peptide bond geometry, was elucidated by a combination of 2D NMR methods and tandem mass spectrometry. The solution state conformation was determined by ROE restrained molecular dynamics calculations. The structural features were found to be similar to those of the crystal structure of the cyclic decapeptide, phakellistatin 8, despite differing peptide sequences.

Wainunuamide, a histidine-containing proline-rich cyclic heptapeptide isolated from the Fijian marine sponge Stylotella aurantium

The isolation and structure determination of an unusual cyclic heptapeptide, wainunuamide, from a Fijian marine sponge, Stylotella aurantium, is reported. The peptide contains three proline residues and a histidine residue, which is rare in cyclic peptides and has only previously been reported in a cyclic peptide isolated from the cyanobacterium Oscillatoria agardhii, suggesting a possible source of the peptide. Wainunuamide is found to have weak cytotoxic activity.

Structure Determination and MSn Analysis of Two New Lissoclinamides Isolated from the Indo–Pacific Ascidian Lissoclinum patella: NOE Restrained Molecular Dynamics Confirms the Absolute Stereochemistry Derived by Degradative Methods

Abstract Two new lissoclinamides, lissoclinamides 9 and 10 were isolated from an Indonesian collection of the ascidian Lissoclinum patella along with the known patellamide C. The structures of the lissoclinamides were determined by a combination of 2D NMR, selective 1D TOCSY, MS and MSn techniques. The assignment of absolute stereochemistry was achieved by the hydrolysis of lissoclinamides 9 and 10 followed by chiral TLC. In the case of lissoclinamide 9, NOE restrained molecular dynamics studies were also performed confirming the proposed stereochemistry.

Metal binding of Lissoclinum patella metabolites. Part 2: Lissoclinamides 9 and 10

Abstract Studies on the Thz, Thn and Oxn containing cyclic peptides, lissoclinamides 9 ( 9 ) and 10 ( 10 ) isolated from the Indo-Pacific ascidian (seasquirt) Lissoclinum patella have delineated their metal binding selectivity. MS and CD competition studies show that lissoclinamide 10 ( 10 ) shows selectivity for Cu 2+ in the presence of an excess of Zn 2+ whereas lissoclinamide 9 ( 9 ) is less selective for Cu 2+ . Comparison of the solution state conformations derived from nOe restrained molecular dynamics and additional Monte–Carlo conformational searches suggested binding environments for the Cu 2+ which confirmed the MS measurements and suggested a reason for the selectivity in the case of lissoclinamides 9 and 10.

Multifidin—A cyanoglucoside in the latex of Jatropha multifida

Abstract A novel non-cyanogenic cyanoglucoside, 1-cyano-3-β- d -glucopyranosyloxy-(Z)-1-methyl-1-propene, was isolated from the latex of Jatropha multifida . The compound was named multifidin.

Podacycline A and B, two cyclic peptides in the latex of Jatropha podagrica

Two novel cyclic peptides were isolated from the latex of Jatropha podagrica, which we named podacycline A and B. Podacycline A is a cyclic nonapeptide with the sequence Gly1-Leu2-Leu3-Gly4-Ala5-Val6-Trp7-Ala8-Gly9+ ++-Gly1. The sequence of podacycline B, a cyclic heptapeptide, was determined to be Phe1-Ala2-Gly3-Thr4-Ile5-Phe6-Gly7-Phe1. The amino acid residues of both compounds were found to have the L-configuration.

Purity determinations in the bulk drug of the novel indoloquinone antitumor agent EO9

SummaryThe pharmaceutical development of the investigational cytotoxic drug EO9 included the structural characterization of the bulk drug by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and infrared (IR) spectroscopy, and analytical characterization by high-performance liquid chromatography and ultraviolet/visible spectrophotometry. The presence of impurities in the bulk drug was investigated. The intermediates in the synthesis of EO9 were structurally characterized by NMR spectroscopy and MS, and analytically characterized by HPLC analysis with photodiode array (PDA) detection. All of the intermediates were below their limits of detection in EO9 bulk drug. The amounts of residual organic solvents were determined by gas chromatography. Methanol and ethanol were detected, but the amounts present did not exceed the limits as set in the United States Pharmacopeia XXII.