Abstract
This study aimed to characterize the antioxidant properties of Rama Forte persimmon, a tannin-rich fruit variety produced in Brazil. Extracts prepared with lyophilized pulps from fruits obtained in local markets were analyzed individually to evaluate the extent of antioxidant protection and investigate the antioxidant mechanism. Iron-mediated hydroxylation of 5,5-dimethyl-1-pirrolidine-N-oxide, determined by electron paramagnetic resonance (EPR), and oxidative degradation of 2-deoxyribose (2-DR) were inhibited by fruit extracts in a dose-dependent manner. There was a considerable individual variability in inhibition of 2-DR degradation by individual fruits. Higher protection of 2-DR degradation (by the extracts) was observed in Fe(III)-citrate/ascorbate in comparison with Fe(III)-EDTA/ascorbate system; however, antioxidant effectiveness of fruit extracts was not diminished by increasing EDTA concentration by 10-fold. Other competition experiments using the 2-DR assay (varying pre-incubation time and 2-DR concentration) indicated that protection comes mainly from free radical scavenging, rather that metal chelation antioxidant activity. Persimmon extracts prevented iron-mediated lipid peroxidation in rat liver homogenates, which correlated significantly with the inhibition of 2-DR oxidation. Finally, sugar content of individual fruits correlated inversely with inhibition of 2-DR degradation, which could indicate that maturation decreases soluble antioxidant concentration or efficiency. In conclusion, lipid peroxidation, 2-DR and EPR experiments indicated that extracts from commercial fruits showed mainly radical-scavenger activity and relevant antioxidant activity.
Highlights
Special interest in the benefits provided by fruits and vegetables has appeared since epidemiological studies showed some degree of correlation among their consumption and reduced risk for coronary heart disease, hypertension and stroke, cancer, diabetes and other degenerative and chronic diseases (Hertog et al, 1993; Liu et al, 2000; How to cite this article Dalvi et al (2018), Antioxidant activity and mechanism of commercial Rama Forte persimmon fruits (Diospyros kaki)
The in vitro antioxidant activity of numerous plant extracts has been well described in the literature and most studies focused mainly on the reducing capacity of different extracts using the Folin-Ciocalteu/Folin-Denis, ABTS or DPPH assays (Wang, Cao & Prior, 1996; Velioglu et al, 1998; Katsube et al, 2004; Miliauskas, Venskutonis & Van Beek, 2004; Gu et al, 2008; Gulcin, 2012; Vinha et al, 2012; Tan & Lim, 2015)
Since chelation of transition metals by polyphenols may interfere with free radical production (Lopes, Schulman & Hermes-Lima, 1999; Andrade et al, 2005; Andrade et al, 2006; Genaro-Mattos et al, 2015; Dalvi et al, 2017), metal chelating capacity of plant extracts may be of pivotal importance, especially when analyzing plant extracts rich in polyphenols—well-known metal-binding molecules (Perron & Brumaghim, 2009)
Summary
Special interest in the benefits provided by fruits and vegetables has appeared since epidemiological studies showed some degree of correlation among their consumption and reduced risk for coronary heart disease, hypertension and stroke, cancer, diabetes and other degenerative and chronic diseases (Hertog et al, 1993; Liu et al, 2000; How to cite this article Dalvi et al (2018), Antioxidant activity and mechanism of commercial Rama Forte persimmon fruits (Diospyros kaki). Boeing et al, 2012; Oyebode et al, 2014; Wang et al, 2014; Micha et al, 2017) Phytochemicals, such as polyphenolic compounds, carotenoids, ascorbate and vitamin E received much attention, mainly due to their antioxidant activity and the relevant role they would play in prevention and treatment of several human diseases (Khan, Afaq & Mukhtar, 2008; Wolfe et al, 2008; Zhang & Tsao, 2016). The in vitro antioxidant activity of numerous plant extracts has been well described in the literature and most studies focused mainly on the reducing capacity of different extracts using the Folin-Ciocalteu/Folin-Denis, ABTS or DPPH assays (Wang, Cao & Prior, 1996; Velioglu et al, 1998; Katsube et al, 2004; Miliauskas, Venskutonis & Van Beek, 2004; Gu et al, 2008; Gulcin, 2012; Vinha et al, 2012; Tan & Lim, 2015). Since chelation of transition metals by polyphenols may interfere with free radical production (Lopes, Schulman & Hermes-Lima, 1999; Andrade et al, 2005; Andrade et al, 2006; Genaro-Mattos et al, 2015; Dalvi et al, 2017), metal chelating capacity of plant extracts may be of pivotal importance, especially when analyzing plant extracts rich in polyphenols—well-known metal-binding molecules (Perron & Brumaghim, 2009)
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