title: Cocos nucifera Linn. (Palmae) husk fiber ethanolic extract: antioxidant capacity and electrochemical investigation.
abstract: The present study aims to determine the antioxidant capacity of the ethanolic extracts of husk fiber of four coconut (Cocos nucifera L.) varieties (yellow dwarf, green dwarf, giant and hybrid) and to evaluate the electrochemical behavior of these extracts on a glassy carbon electrode and on a modified glassy carbon electrode. The highest values of total phenolic content were obtained for the hybrid (531 ± 24 mg GAE g(-1) dry extract) and yellow dwarf (501 ± 29 mg GAE g(-1) dry extract) varieties and the lowest was for the green dwarf variety with 58 ± 9 mg GAE g(-1) dry extract. The ability of the extracts to scavenge DPPH˙ radicals was in the order of giant > yellow dwarf > hybrid > green dwarf and the IC50 values varied from 8.6 to 55.9 μg mL(-1). All varieties showed reducing potential by the use of FRAP and CUPRAC methods, with the lowest performance obtained for the green dwarf variety. Additionally, through the use of mimetic biomembranes, ethanolic extracts of coconut husk were shown to protect lipids against oxidative damage independent of the variety. The main antioxidants identified in the extract of yellow dwarf variety by UPLC-MS were quercetin and catechin. Cyclic voltammetric studies of the ethanolic extracts on glassy carbon electrode confirmed the presence of easily oxidized compounds, and the high antioxidant capacity of the varieties. This capacity was expressed as mg quercetin equivalents g(-1) dry extract and ranged from 25.9 up to 53.5 mg QE g(-1). A poly-xanthurenic acid (poly-Xa)/multi-walled carbon nanotube (MWCNT) / glassy carbon modified electrode (poly-Xa/MWCNT/GCE) was used for this purpose. Our findings suggest that these extracts are potentially important antioxidant supplements for the everyday human diet, pharmaceutical and cosmetic industries, thereby aggregating value to the enormous amount of waste from the coconut industry, mostly used for burning purposes.
authors.affiliation: Instituto de Química e Biotecnologia, Universidade Federal de Alagoas (UFAL), Tabuleiro do Martins, Maceio, AL, Brazil.
authors.forename: Monika Bezerra dos Santos
authors.initials: MB
authors.lastname: Oliveira
authors.forename: Iara Barros
authors.initials: IB
authors.lastname: Valentim
authors.forename: Camila Calado
authors.initials: CC
authors.lastname: de Vasconcelos
authors.forename: Cristhiane Maria Bazílio
authors.initials: CM
authors.lastname: Omena
authors.forename: Etelvino José Henriques
authors.initials: EJ
authors.lastname: Bechara
authors.forename: João Gomes
authors.initials: JG
authors.lastname: da Costa
authors.forename: Mikael de Lima
authors.initials: Mde L
authors.lastname: Freitas
authors.forename: Antônio Euzébio Goulart
authors.initials: AE
authors.lastname: Sant'Ana
authors.forename: Marília Oliveira Fonseca
authors.initials: MO
authors.lastname: Goulart
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000737:chemistry; D003059:Cocos / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods; D000431:Ethanol / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D010851:Picrates / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D005609:Free Radicals; D010851:Picrates; D010936:Plant Extracts; D000431:Ethanol; C004931:1,1-diphenyl-2-picrylhydrazyl