Analysis of neem oils by LC-MS and degradation kinetics of azadirachtin-A in a controlled environment. Characterization of degradation products by HPLC-MS-MS
| Autor: | Barrek, Sami, Païssé, Jean-Olivier, Grenier-Loustalot, Marie-Florence |
|---|---|
| Přispěvatelé: | Service Central d'Analyse (SCA), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC) |
| Rok vydání: | 2003 |
| Předmět: |
Limonins
HPLC chromatography Spermatophyta Magnetic Resonance Spectroscopy Light NMR spectrometry Sample preparation Dicotyledones Mass Spectrometry Glycerides [CHIM.ANAL]Chemical Sciences/Analytical chemistry Meliaceae Pesticides Insecticide Chromatography High Pressure Liquid degradation Azadirachta indica azadirachtin-A Degradation product Terpenes Chemical ionization HPLC-MS-MS Temperature Triterpenoids Electrospray Kinetics Angiospermae Liquid liquid extraction Atmospheric pressure Comparative study Mass spectrometry MS/MS Neem |
| Zdroj: | Analytical and Bioanalytical Chemistry Analytical and Bioanalytical Chemistry, Springer Verlag, 2004, 378 (3), pp.753-763. ⟨10.1007/s00216-003-2377-0⟩ |
| ISSN: | 1618-2642 1618-2650 |
| DOI: | 10.1007/s00216-003-2377-0⟩ |
| Popis: | International audience; Since it was first isolated, the oil extracted from seeds of neem (Azadirachtin indica A juss) has been extensively studied in terms of its efficacy as an insecticide. Several industrial formulations are produced as emulsifiable solutions containing a stated titer of the active ingredient azadirachtin-A (AZ-A). The work reported here is the characterization of a formulation of this insecticide marketed under the name of Neem-azal T/S and kinetic studies of the major active ingredient of this formulation. We initially performed liquid-liquid extraction to isolate the neem oil from other ingredients in the commercial mixture. This was followed by a purification using flash chromatography and semi-preparative chromatography, leading to (13)C NMR identification of structures such as azadirachtin-A, azadirachtin-B, and azadirachtin-H. The neem extract was also characterized by HPLC-MS using two ionization sources, APCI (atmospheric pressure chemical ionization) and ESI (electrospray ionization) in positive and negative ion modes of detection. This led to the identification of other compounds present in the extract-azadirachtin-D, azadirachtin-I, deacetylnimbin, deacetylsalannin, nimbin, and salannin. The comparative study of data gathered by use of the two ionization sources is discussed and shows that the ESI source enables the largest number of structures to be identified. In a second part, kinetic changes in the main product (AZ-A) were studied under precise conditions of pH (2, 4, 6, and 8), temperature (40 to 70 degrees C), and light (UV, dark room and in daylight). This enabled us to determine the degradation kinetics of the product (AZ-A) over time. The activation energy of the molecule (75+/-9 kJ mol(-1)) was determined by examining thermal stability in the range 40 to 70 degrees C. The degradation products of this compound were identified by use of HPLC-MS and HPLC-MS-MS. The results enabled proposal of a chemical degradation reaction route for AZ-A under different conditions of pH and temperature. The data show that at room temperature and pH between 4 and 5 the product degrades into two preferential forms that are hydrolyzed to a single product over time and as a function of pH change. |
| Databáze: | OpenAIRE |
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