title: Coffee silverskin: a possible valuable cosmetic ingredient.
abstract: BACKGROUND
  Currently, there is a great tendency in cosmetic area to use natural extracts. Coffee silverskin (CS) is the most abundant solid by-product generated during roasting of coffee processing.
  
  
  OBJECTIVE
  To evaluate different CS extracts as promising cosmetic ingredients, regarding antioxidant, antimicrobial, and cytotoxic properties.
  
  
  METHODS
  Aqueous, hydroalcoholic and ethanolic CS extracts were obtained by an environmentally friendly procedure considering costs and pollution. Extracts were characterized for total phenolic and flavonoid contents (TPC and TFC, respectively), antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), antimicrobial activity expressed as minimal inhibitory concentration (MIC) and cytotoxicity using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase (LDH) assays in two skin cell lines (fibroblasts and keratinocytes).
  
  
  RESULTS
  The TPC of extracts was 18.33-35.25 mg of gallic acid equivalents per g of material on a dry basis (mg GAE/g db). The TFC of extracts was 1.08-2.47 µg cathechin equivalents per g dry material (µg CE/g db). The antioxidant activity was high, with values ranging between 95.95 and 216.40 µmol Fe(2+)/g for aqueous and alcoholic samples, respectively. Preliminary assays for antimicrobial potential showed that extracts display antibacterial activity. The MIC varied from 31.3 to 250 µg/mL for Gram-positive, and from 31.3 to 1000 µg/mL for Gram-negative. Extracts did not affect in vitro cell viability, with values near 100% in all concentrations tested.
  
  
  CONCLUSIONS
  RESULTS seem show that CS is a safe source of natural antioxidants with antifungal and antibacterial activity and no cytotoxicity, with potential usefulness for cosmetic applications.
authors.affiliation: Department of Chemical Sciences, Faculty of Pharmacy, REQUIMTE, University of Porto , Porto , Portugal .
authors.forename: Francisca
authors.initials: F
authors.lastname: Rodrigues
authors.forename: Ana
authors.initials: A
authors.lastname: Palmeira-de-Oliveira
authors.forename: José
authors.initials: J
authors.lastname: das Neves
authors.forename: Bruno
authors.initials: B
authors.lastname: Sarmento
authors.forename: M Helena
authors.initials: MH
authors.lastname: Amaral
authors.forename: M Beatriz P P
authors.initials: MB
authors.lastname: Oliveira
mesh_terms: D000900:Anti-Bacterial Agents / Q000302:isolation & purification* / Q000494:pharmacology; D000975:Antioxidants / Q000302:isolation & purification* / Q000494:pharmacology; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D003069:Coffee; D003358:Cosmetics / Q000302:isolation & purification* / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D010936:Plant Extracts / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000975:Antioxidants; D003069:Coffee; D003358:Cosmetics; D005419:Flavonoids; D010936:Plant Extracts
keywords: Agro-industrial by-products; antimicrobial activity; antioxidant activity; coffee industry residues; cosmetics; cytotoxicity; innovative revalorization of coffee by-products; skin care