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Vibrational spectroscopy of betulinic acid HIV inhibitor and of its birch bark natural source

Domenii publicaţii > Fizica + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Simona Cinta Pinzaru, N. Leopold, W. Kiefer

Editorial: Ref. NR. TAL 4184, Elsevier, Colloquium Spectroscopicum Internationale, CSI XXXII, Pretoria, South Africa, Vol. Abstracts,TH 4-4, 2001.Talanta, 57/4, p.625-631, 2002.

Rezumat:

Betulinic acid [BA, 3b-hydroxy-20(19)-lupaen-28-oic acid] can be chemically derived from betulin, a substance found in abundance in the outer bark of white birch trees (Betula alba). This molecule is a pentacyclic triterpene, difficult to be solved for spectroscopic experiments. The bark which this birch sheds naturally and causes its white appearance, abundantly provides the BA in the form of betulin. BA has been found to induce apoptosis, cell death, in melanoma cells, without impacting healthy tissue [1]. BA has already shown promise against specific strains of HIV 1 and may lead to further understanding of a mechanism involving a post-binding step in replication of the virus. [2, 3]. BA acts as an early stage of the viral cycle by inhibiting the fusion of the outer coating of the virus with the membrane of the target cell. Reports on inhibiting the fusion of the HIV with the cell membrane mentioned only peptides and monoclonal antibodies [1]. However, the mechanisms were not completely understood [2,3] and the betulinic acid and its derivatives require further research to demonstrate their potential anti-HIV-1 activity in man. The properties of BA make it an interesting candidate to be taken under exhaustive spectroscopic study.
Here we report the vibrational Raman, IR and surface enhanced Raman investigations of the BA molecule in order to get information about the structure and behaviour of BA molecule in free or adsorbed state and about its natural provider, the birch bark. The bark samples were collected from different areas of Transilvania, Romania and directly used for micro-Raman or powdered for tablets in FT-IR spectroscopy. Vibrational characterisation is reported and further, advantages of the multichannel detection with long acquisition time were employed for SERS of BA molecule. The presence of the enhanced ns(COO) mode in the SERS spectrum of BA suggests a chemisorption of the molecule on the surface [4].

Cuvinte cheie: Raman, SERS, betulinic acid-HIV inhibitor