Electron impact and chemical ionization mass spectral analyses of methyl esters species of free mycolic acid fraction from Rhodococcus lentifragmentus

The free mycolic acid fraction from Rhodococcus lentifragmentus was derivatized to methyl esters and further fractionated into saturated (F-0), monounsaturated (F-1) and diunsaturated (F-2) species using argentation-TLC. Methyl esters fractions F-0, F-1 and F-2, accounting for approximately 7.4%, 53.1% and 39.5%, respectively, were analyzed by electron impact (EI) and chemical ionization (CI) mass spectrometries. According to EI-MS, peaks observed for M(+)-18, that were prominent compared to those representing M(+)-32 and M(+)-(18 + 32), indicated that the carbon chain size ranged from C-36 to C-48. The pyrolytic cleavage of methyl mycolates (R(2)-CHOH-CH(R(1))-COOCH3), following the McLafferty rearrangement released fragment ions corresponding to, (a) the alpha-subunit, representing the fatty acid methyl ester (R(1)-CH2-COOCH3), methyl hexadecanoate, methyl tetradecanoate and methyl dodecanoate in decreasing order of relative intensity of peaks, and (b) the beta-subunit, representing the meroaldehyde moiety (R(2)-CHO). The saturated meroaldehyde species exhibited peaks representing meroaldehyde minus 18 mass units in which R(2) ranged from C19H39 to C31H63. The monunsaturated species exhibited peaks representing the meroaldehyde in which R(2) ranged from C19H37 to C31H61; peaks corresponding to meroaldehyde minus 18 mass units appeared only in the most abundant components, C29H57CHO, C27H53CHO, C25H49CHO and C31H61CHO, in a decreasing order of relative abundance. The diunsaturated species exhibited peaks essentially corresponding to meroaldehyde in which R(2) corresponded to C31H59 and C29H55; the latter displayed a relative intensity that was about one-half compared to that of the former. Fractions F-0, F-1 and F-2 showed a more intense pyrolytic fragmentation under CI-MS in contrast to results found under EI-MS. Therefore, peaks representing the alpha-subunit and the beta-subunit were more prominent than the ones representing the fragmentation of the hydrocarbon chain. Moreover, the beta-subunit of saturated species exhibited peaks corresponding to meroaldehyde plus hydrogen, and no dehydration of the beta-subunit occurred in this case. In turn, the beta-subunit of monounsaturated and diunsaturated species showed peaks representing both the meroaldehyde plus hydrogen and its dehydration product plus hydrogen. Thus, the presence of unsaturation in the meroaldehyde subunit of methyl mycolate facilitates appearance of dehydration fragment ions under chemical ionization procedure.

Isolation and chemical characterization of PwTx-II: A novel alkaloid toxin from the venom of the spider Parawixia bistriata (Araneidae, Araneae)

Brazil has many species of spiders belonging to Araneidae family however, very little is known about the composition, chemical structure and mechanisms of action of the main venom components of these spiders. The main objective of this work was to isolate and to perform the chemical characterization of a novel beta-carboline toxin from the venom of the spider Parawixia bistriata, a typical species of the Brazilian 'cerrado'. The toxin was purified by RP-HPLC and structurally elucidated by using a combination of different spectroscopic techniques (UV, ESI-MS/MS and H-1 NMR), which permitted the assignment of the molecular structure of a novel spider venom toxin, identified as 1-4-guanidinobutoxy-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline, and referred to here as PwTx-II. This compound is toxic to insects (LD50 = 12 +/- 3 eta g/mg honeybee), neurotoxic, convulsive and lethal to rats (LD50 = 9.75 mg/kg of male Wistar rat). (c) 2005 Elsevier Ltd. All rights reserved.

Thermal Characterization and Cytotoxicity of Complexes Formed by Papain and Cyclodextrin

Papain is a proteolytic enzyme with restricted applications due to its limited stability. Cyclodextrins are widely used in pharmaceutical formulations once they are able to form complexes with other molecules, improving their stability and bioavailability. The purpose of the present paper was to analyze complexes formed by papain/hydroxypropyl-beta-cyclodextrin and papain/beta-cyclodextrin by thermal analysis and cytotoxicity tests to verify their possible interactions and toxicological behavior. Complex solutions were prepared at different molar ratios and collected as a function of time to be lyophilized and analyzed. Results showed changes in endothermic events and cytotoxicity profiles. A complex formation for both complexes is observed; nevertheless, beta-cyclodextrin was able to change the enzyme characteristics more efficiently.

Synthesis, thermal properties and spectroscopic study of solid mandelate of light trivalent lanthanides

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal decomposition and stability in a series of tetrafluorborate copper(I) complexes

Tetrafluorborate copper(I) complexes containing acetonitrile, triphenylphosphine, 1,10-phenanthroline, 2,2′-bipyridine and 2-quinolinethiol have been prepared in order to study their thermal stabilities as a function of the ligands present. The characterization of the above compounds was carried out by elemental analysis and IR spectroscopy. Their thermal behaviour has been investigated and the final products were identified by X-ray powder diagrams. © 1995.

Plant Cell Wall Research Related to Evolution and Chemical Defenses

The plant cell wall is composed mainly of polysaccharides some constituted of repeating units of a single sugar, as cellulose or by two or more sugars grouped in repeating oligosaccharide blocks as the galactomannans and xyloglucans. Variations in composition and fine structure of these cell wall polysaccharides have been used as taxonomic markers and in the comprehension of the evolutive process, particularly in the Leguminosae. Partial hydrolysis of these compounds give rise to oligomers, some of which are capable of eliciting the synthesis of defensive substances in plants named phytoalexins. Species which differ in respect to phytoalexin liberation also differ in cell wall composition, particularly in the pectic fraction of the wall. Pectinases (mainly endopolygalacturonases) present in fungi, have been shown to hydrolyze plant cell walls yielding phytoalexin-eliciting oligosaccharides which differ in composition and in eliciting capacity in different species. These differences can be associated with the capacity of a given species to produce phytoalexins. On the other hand, the phytoalexin induction in plants is being used as a method of producing novel bioactive secondary metabolites.

Byrsonima crassa Niedenzu (IK): Antimicrobial activity and chemical study

The methanolic extract of leaves from Byrsonima crassa, a Brazilian medicinal plant, was analyzed by CC and HPLC. Four constituents were isolated and identified as quercetin, methyl gallate, (-)-epigallocatechin gallate and quercetin-3-O-(2″-galloyl)-α-L-arabinopyranoside. The methanolic and hydromethanolic extract, as well as fractions, were evaluated regarding their possible antimicrobial activity using in vitro methods. Results showed that both extracts and fractions exhibited significant antimicrobial activity against all tested strains.

Physical and chemical characterization of dovyalis fruits

The objective of this work was to establish physical and chemical characterizations of dovyalis hybrid fruits (Dovyalis abyssinica and D. hebecarpa). Samples of 25 fruits were characterized by evaluation of length and width, weight, percentage and number of seeds per fruit, peel percentage, pulp percentage, total soluble solids (TSS), titratable acidity (TA), vitamin C and TSS/TA ratio. Dovyalis fruit has good physical quality for market with an average of 75% pulp. Vitamin C content averaged 120.3 mg/100 g of fresh fruit, characterizing dovyalis as a good source of vitamin C. © 2005 by The Haworth Press, Inc. All rights reserved.