Abstract
The antioxidant activity of Psychotria carthagenensis, P. leiocarpa, P. capillacea and P. deflexa (Rubiaceae) extracts were investigated, and the concentrations of total phenolics, flavonoids, condensed tannins and flavonols were determined. The chemical compositions of the extracts were investigated using the high performance liquid chromatography (HPLC/PAD) method. We used 1,1-diphenyl-1-picrylhydrazyl free radical (DPPH), β-Carotene bleaching and 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cations to determine antioxidant activity. The ability to scavenge radical was measured in these experiments by the discoloration of the solution. Concentrations of constituents were measured spectrophotometrically. P. carthagenensis and P. capillacea exhibited the highest antioxidant activity, in the DPPH test, β-carotene bleaching and ABTS system. The highest phenolic, flavonoid, condensed tannin and flavonol concentration was found in P. carthagenensis and P. capillacea extracts. HPLC-PDA analysis of P. carthagenensis and P. capillacea revealed hydroxycinnamic acid (p-coumaric acid). This is the first report on the antioxidant properties and constituent analysis of these Psychotria extracts.
Highlights
Antioxidants, molecules with a radical-scavenging capacity, are thought to exert a protective effect against free radical damage
The β-carotene bleaching method [44] evaluates the ability of a substance to prevent the oxidation of β-carotene, protecting it from the free radicals generated during the peroxidation of linoleic acid
The scavenging effect of extracts from Psychotria and standard on ABTS+ decreased in the order: butylated hydroxyltoluene (BHT) ~ P. carthagenensis P. capillacea ~ ascorbic acid P. deflexa ~ P. leicocarpa (96.4% ± 2.44%, 92.5% ±7.43%, 87.34% ±8.32%, 80.9% ±5.56%, 15.58% ±5.22% and 12.20% ±4.44%, respectively) at the same concentration (100 μg/mL)
Summary
Antioxidants, molecules with a radical-scavenging capacity, are thought to exert a protective effect against free radical damage. Reported phytochemical studies on the Psychotria genus showed alkaloids, mainly polypirrolidinoindole [7,8,9,10,11,12,13], quinolines [14,15,16,17,18,19], and monoterpene indole alkaloids [20,21,22,23,24,25,26]. Was isolated an N-glycosylated monoterpenoid indole alkaloid N, β-D-glucopyranosyl vincosamide, constitutes up to 2.5% of the dry weight in leaves [31], and iridoid glucosides asperuloside and deacetylasperuloside [32] Study showed that this alkaloid may act indirectly in P. leiocarpa protection against oxidative stress generated upon wounding, UV exposure, and perhaps other environmental stresses [33]. We determined the concentrations of phenolic compounds, condensed tannins, flavonoids, and flavonol
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