Modeling photoprotection in Andean plants: deactivation pathways of excited-states of main flavonoids present in Zuccagnia punctata Cav

M. MARTIN; F. E. MORÁN VIEYRA; C. D. BORSARELLI

Mendoza

Congreso; 21st INTER-AMERICAN PHOTOCHEMICAL SOCIETY CONFERENCE; 2011

UBA - IAPS

Sunlight irradiance is of major importance for all living organisms, in particular as main source of energy for plants and the majority of bacteria. However, an increment of the input of the sunlight irradiation, especially of the ultraviolet radiation (UV), can affect seriously the cellular systems and compromise the survival of several species. In recent decades, the amount of UV radiation that penetrates the earth's surface has increased from 1% to 3% per year due to the alarmingly weakening of the O3 layer. Considering that UVA represents >95% of the UV radiation incident on the Earth’s surface, in the present work we explore the photophysical and photochemical properties of the flavonoids present in the leaves of the Andean shrub Z. punctata: 7-hydroxyflavanone (7HF), 2’,4’-dihydroxychalcone (DHC), and 3,7-dihydroxyflavone (DHF) in solution upon UVA excitation in order to characterize the deactivation pathways of their excited states and evaluate their functionality as photoprotective biocompounds. Interesting, among theses studied flavonoids, the chalcone DHC showed the highest molar absorption coefficient in the UVA range (320  20000 M-1cm-1), and also the lowest quantum yield of photodegradation ( 0.1%). Basically, the energy degradation mechanism is through non-radiative processes from the singlet state, since no fluorescence was detected for this compound (F