Abstract
The genus Swietenia (Meliaceae) has a wide variety of secondary metabolites with reported antioxidant activity, such as flavonoids and limonoids. In the present study, the antioxidant capacity, along with the phenol and flavonoid contents of the leaf extracts of three species of this genus: Swietenia mahagoni, Swietenia macrophylla, and Swietenia humilis were evaluated. The antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), ferric reducing/antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) methods. The results showed that the three species had significant antioxidant activity and substantial contents of phenolic compounds and flavonoids. The species S. macrophylla was the most effective, and compounds with recognized antioxidant capability were detected by gas chromatography coupled with mass spectrometry (GC-MS). Catechin was the most abundant constituent in the active fractions, and was confirmed and quantified by high performance liquid chromatography (HPLC). Key words: Swietenia macrophylla, antioxidant, (+)-catechin, flavonoids, phenols.
Highlights
Free radicals and other reactive oxygen species (ROS) are produced constantly in metabolic reactions of aerobic organisms
For the DPPH, ABTS and ferric reducing/antioxidant power (FRAP) assays, the species S. macrophylla had the highest activity followed by S. mahagoni, which was in accordance with previous reports (Falah et al, 2008; Matsuse et al, 1997; Rahman et al, 2014; Sahgal et al, 2009)
If the antioxidant potential of the extracts is due to the presence of flavonoids or other phenols (Es-Safi et al, 2007), it has to be considered that the radical DPPH does not react with flavonoids that do not have hydroxyl groups in the B ring, or phenols that have only one hydroxyl group (Roginsky and Lissi, 2005)
Summary
Free radicals and other reactive oxygen species (ROS) are produced constantly in metabolic reactions of aerobic organisms. Aerobic organisms have a natural defensive system of enzymatic and non-enzymatic mechanisms of detoxification of these radicals. When this endogenous system fails, the cell goes into a stage of oxidative stress responsible for cellular degeneration. In this way, free radicals and other ROS can react with proteins, lipids, and DNA, causing irreversible damages (Donaldson et al, 1996). Antioxidant molecules that are able to donate electrons to stabilize free radicals
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