LAGORIO MarÍa Gabriela
congresos y reuniones científicas
Polyphenols content in different parts of an aromatic plant and its relation with blue fluorescence
Encuentro; Segunda Reunión de Fotobiólogos Moleculares Argentinos (II GRAFOB),; 2013
Institución organizadora:
Asociación de fotobiólogos moleculares argentinos
Contenido de polifenoles en distintas partes de una planta aromática y su relación con la fluorescencia azul Polyphenols content in different parts of an aromatic plant and its relation with blue fluorescence. Natalia Adler,1 Johanna Mendes Novo,1 Analia Iriel,2 M. Gabriela Lagorio1   1 INQUIMAE / Dpto. de Química Inorgánica, Analítica y Química Física. Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Ciudad Universitaria. Pabellón II, 1er piso, C1428EHA, Buenos Aires, Argentina 2 Centro de Estudios Transdisciplinarios del Agua, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Av. Chorroarín 280, C1427CWO, Buenos Aires, Argentina,     Origanum vulgare L. belongs to Lamiaceae family and it is used in medicine, cosmetic and food flavoring. Its beneficial action on health is mainly due to the presence of phenolic compounds: flavonoids, as quercetin and Kaempferol, and phenolic acids as rosmarinic, ferulic, p-coumaric, chlorogenic and caffeic acids. Most of these compounds have antioxidant properties and are reported in literature to emit fluorescence in the blue-green region when they are in solution. It is reasonable to think that they could then emit fluorescence when included in the plant material, specially in the dry state where non-radiative decays are minimized. Plants of Origanum vulgare L. display higher emission when they are dry. In fact, they emit the typical chlorophyll fluorescence in the red (680 nm) and in the far-red (735 nm) in addition to an important fluorescence at 480 nm (blue) and 530 nm (green).(1)   The aim of the present work is to determine the content of total polyphenols and chlorophylls in the various parts of the dry plant and to compare the results with the fluorescence signals of the intact material in the blue, green and red region of the electromagnetic spectrum. The underlying objective is to look for optical signals capable of sensing nutraceutical contents.   The total polyphenols contents (TPC) were determined on dry inflorescences, leaves and stems by the Folin Ciocalteau´ s method using spectrophotometry and gallic acid as standard for the calibration curve (2). The total polyphenols content was expressed as gallic acid equivalents in g per 100 g dry sample. Chlorophyll-a and chlorophyll-b content was determined spectrophotmetrycally. Approximately 0.4 g of leaves were weighed and ground in a mortar with 5 ml of 80% v/v acetone?water. The suspension was filtered by suction and the residue treated again with 80% acetone until no more chlorophyll was extracted from it. The absorbance of the solution placed in a 10 mm pathlength cell, was read as a function of wavelength using a spectrophotometer (UV 3101 Shimadzu). Chlorophyll-a, chlorophyll-b and total Chlorophylls (Chl) concentrations were calculated according to reference (3). Emission spectra of dry inflorescences, leaves and stems were obtained under low photon flux conditions on a PTI Model QM-1 spectrofluorometer with a front-face arrangement. Fluorescence spectra were recorded from 420 to 800 nm using an excitation wavelength of 400 nm. From these spectra, fluorescence ratios between blue, green, red and far red maxima were calculated   Total polyphenols content was similar for leaves and inflorescences and they were appreciably lower for stems. Total chlorophyll content decreased in the order: leaves, inflorescences and stems. Additionally, we have demostrated that higher content ratios TPC/Chl were found for the parts displaying higher fluorescence ratio blue/far-red.   References 1-Mendes Novo, J., Iriel, A., Marchi, M. C., Lagorio, M. G., sent to Photochem. Photobiol. in march 2013 2-Anesini, C., Ferraro, G. E, Filip, R., J. Agric. Food Chem., 56, 9225, 2008 3-Cordon, G. B., Lagorio, M. G., Photochem. Photobiol. Sci., 5, 735, 2006