INVESTIGADORES
ISLA Maria Ines
congresos y reuniones científicas
Título:
Charge-Transfer Quenching of Singlet Oxygen O2(1ƒ´g) by Structurally Related Flavonoids from Zuccagnia punctata Cav
Autor/es:
ZAMPINI I.C.,; ORDOÑEZ R.,; ISLA M.I.,; MORÁN VIEYRA F.,; BORSARELLI C
Lugar:
Cordoba,Argentina
Reunión:
Conferencia; CLAFQO-9. 9th Latin American Conference on Physical Organic Chemistry; 2007
Institución organizadora:
Sociedad de Fisico-quimica
Resumen:
Zuccagnia punctata Cav.  (Fabaceae), commonly named jarilla macho is a Argentinean native shrub widely distributed in semiarid and arid western regions, and their extracts an infusions are traditionally used for the treatment of infections, asthma, arthritis, rheumatism, tumors, etc. Most of these health linked properties of Z. punctata extracts are attributed to antioxidant functions. The leaves of Z. punctata contains important amounts of flavonoids, mainly the structurally related series 2’,4’-diOH-chalcone (DHC), 7-OH-flavanone (HF), and 7-OH-flavonol (DHF). In this work, the quenching ability of singlet oxygen O2(1Δg) by HF, DHF and DHC in ethanolic solutions was evaluated using both stationary and time-resolved techniques. The rate constant for both the chemical (kr) and physical (kq) quenching of O2(1Δg) were determined. A linear free-energy relationship (LFER) between the log(kr or kq) vs. the half-wave oxidation potential (E1/2ox) of the flavonoids was found, being the slope value much larger for the reactive tan for the physical quenching. An exciplex mediated mechanism is proposed for the process, where electron donor capacity of the flavonoids governs the proportion of chemical and physical quenching. In this work, the quenching ability of singlet oxygen O2(1Δg) by HF, DHF and DHC in ethanolic solutions was evaluated using both stationary and time-resolved techniques. The rate constant for both the chemical (kr) and physical (kq) quenching of O2(1Δg) were determined. A linear free-energy relationship (LFER) between the log(kr or kq) vs. the half-wave oxidation potential (E1/2ox) of the flavonoids was found, being the slope value much larger for the reactive tan for the physical quenching. An exciplex mediated mechanism is proposed for the process, where electron donor capacity of the flavonoids governs the proportion of chemical and physical quenching. In this work, the quenching ability of singlet oxygen O2(1Δg) by HF, DHF and DHC in ethanolic solutions was evaluated using both stationary and time-resolved techniques. The rate constant for both the chemical (kr) and physical (kq) quenching of O2(1Δg) were determined. A linear free-energy relationship (LFER) between the log(kr or kq) vs. the half-wave oxidation potential (E1/2ox) of the flavonoids was found, being the slope value much larger for the reactive tan for the physical quenching. An exciplex mediated mechanism is proposed for the process, where electron donor capacity of the flavonoids governs the proportion of chemical and physical quenching. (Fabaceae), commonly named jarilla macho is a Argentinean native shrub widely distributed in semiarid and arid western regions, and their extracts an infusions are traditionally used for the treatment of infections, asthma, arthritis, rheumatism, tumors, etc. Most of these health linked properties of Z. punctata extracts are attributed to antioxidant functions. The leaves of Z. punctata contains important amounts of flavonoids, mainly the structurally related series 2’,4’-diOH-chalcone (DHC), 7-OH-flavanone (HF), and 7-OH-flavonol (DHF). In this work, the quenching ability of singlet oxygen O2(1Δg) by HF, DHF and DHC in ethanolic solutions was evaluated using both stationary and time-resolved techniques. The rate constant for both the chemical (kr) and physical (kq) quenching of O2(1Δg) were determined. A linear free-energy relationship (LFER) between the log(kr or kq) vs. the half-wave oxidation potential (E1/2ox) of the flavonoids was found, being the slope value much larger for the reactive tan for the physical quenching. An exciplex mediated mechanism is proposed for the process, where electron donor capacity of the flavonoids governs the proportion of chemical and physical quenching.2(1Δg) by HF, DHF and DHC in ethanolic solutions was evaluated using both stationary and time-resolved techniques. The rate constant for both the chemical (kr) and physical (kq) quenching of O2(1Δg) were determined. A linear free-energy relationship (LFER) between the log(kr or kq) vs. the half-wave oxidation potential (E1/2ox) of the flavonoids was found, being the slope value much larger for the reactive tan for the physical quenching. An exciplex mediated mechanism is proposed for the process, where electron donor capacity of the flavonoids governs the proportion of chemical and physical quenching.