
Quenching of singlet molecular oxygen by natural furan diterpenes
1997; Elsevier BV; Volume: 38; Issue: 2-3 Linguagem: Inglês
10.1016/s1011-1344(96)07444-1
ISSN1873-2682
AutoresPaolo Di Mascio, Marisa Helena Gennari de Medeiros, Helmut Sies, Sonia G. Bertolotti, Silvia E. Braslavsky, Dorila Piló‐Veloso, Beatriz Helena L. Noronha Sales, Eva G. Magalhães, Raimundo Braz‐Filho, Etelvino José Henriques Bechara,
Tópico(s)Antioxidant Activity and Oxidative Stress
ResumoSinglet molecular oxygen O2(1Δg) is a reactive oxygen species capable of damaging biological molecules and triggering oxidative stress. The quenching of this species by naturally occurring furans was measured using O2(1Δg) from two different sources: (1) the thermal decomposition of 1,4-dimethylnaphthalene endoperoxide (1,4-DMNO2); (2) tetraphenylporphyrin sulphonate photosensitization. Four furan diterpenes were isolated from alcoholic extracts of Sucupira branca (Pterodon sp., Leguminosae) seeds, which are used for the treatment of rheumatic diseases, suggesting anti-inflammatory activity. Using time-resolved near-IR (NIR) emission after photosensitization, the overall (physical + chemical) O2(1Δg) quenching rate constants by these compounds were found to be of the order of 108 M−1s−1, with the exception of the conjugated furan diterpenes 3,5,6-trimethoxy-7,8-furano-3′,4′-methylenedioxy-2″,3″-flavane and 3,4,5,6-tetramethoxy-7,8-furano-2″,3″-flavane for which 20-fold lower values were observed. These lower values are attributed to the conjugation of the furan moiety with the aromatic ring, which prevents (2 + 4) cucloaddition of O2(1Δg) to the furan ring. Although the non-conjugated furans exhibit a low scavenging effect on lipid peroxidation in microsomes, their high O2(1Δg) quenching constant may minimize the extent of tissue damage associated with the inflammatory process.
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