[Todos] Seminario departamental DQIAyQF/ INQUIMAE Lunes 2 de diciembre

[andrea en qi.fcen.uba.ar]

Lunes 2 de diciembre, 13 hs
Aula Seminarios INQUIMAE, 3er piso

The Photo(Chemistry) of Natural Plant Pigments: The Anthocyanins

Dr. Frank H. Quina
Instituto de Química, Universidade de São Paulo
São Paulo, Brazil


        Anthocyanins (from the Greek words for flower, anthos, and blue,
kyanos)
are the principal pigments responsible for the red, blue, and purple
colors of plants. The colors of anthocyanins can range from yellow to
purple and depend on the substituents present, the local pH, the state of
aggregation of the anthocyanins, or complexation by organic molecules or
metal cations. For more than a century, biologists, biochemists, and
plant physiologists have hypothesized as to the possible biological roles
of anthocyanins in plants. In flowers and fruit, the colors imparted by
anthocyanins presumably serve to attract pollinators or indicate
ripeness, respectively. In vegetative tissues such as leaves, a leading
hypothesis is that they protect the photosynthetic apparatus from the
effects of excess incident visible or UV-B radiation and photooxidative
stress.
        Over the last decade or so, we have investigated the chemistry and
photophysics of natural anthocyanins and of model compounds containing
the basic anthocyanin chromophore in order to elucidate the structural
and environmental factors that control the ground and excited state
reactivity of anthocyanins and their complexes with organic molecules.
The photophysics of anthocyanins, which include ultrafast proton transfer
and/or charge-transfer mediated quenching, are fully consistent with the
proposed photoprotective role in leaves. Current interests include the
use of the ultrafast proton transfer from excited anthocyanins to study
proton migration and dynamics at surfaces and the development of
strategies for the encapsulation of anthocyanins that lead to greater
stabilization of their color.
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