title: Formaldehyde replacement with glyoxylic acid in semipermanent hair straightening: a new and multidisciplinary investigation.
abstract: OBJECTIVE
  Formaldehyde is an effective and popular semipermanent hair straightener, but the severe consequences for human health due to its toxicity have prompted the search for safer alternatives. Different carbonyl compounds, including glyoxylic acid, have recently been proposed as promising candidates. Despite the interest in this topic, there is a lack of information about the interactions between hair keratin and straightener agents. This study addresses this issue to gain new insights useful in the development of new products for safe, semipermanent hair deformation.
  
  
  METHODS
  The possible reactions occurring between carbonyl groups and nucleophilic sites on amino acid residues belonging to the keratin were investigated using as model compounds some aldehydes and amino acid derivatives. Raman and IR analyses on yak hair subjected to the straightening treatment with glyoxylic acid in different conditions were carried out. Scanning electron microscope (SEM) analyses were carried out on yak and curly human hair after each step of the straightening procedure.
  
  
  RESULTS
  The reactions between aldehydes and N-α-acetyl-L-lysine revealed the importance of the carbonyl electrophilicity and temperature to form imines. Raman and IR analyses on yak hair subjected to the straightening treatment evidenced rearrangements in the secondary structure distribution, conformational changes to the disulphide bridges, a decrease of the serine residues and formation of imines. It was also indicated that straightening produced major conformational rearrangements within the hair fibre rather than on the cuticle.
  
  
  CONCLUSIONS
  This investigation revealed the role played by the electrophilicity of the carbonyl on the straightener agent and of the temperature, closely related to the dehydration process. Raman and IR studies indicated the involvement of imine bonds and the occurrence of a sequence of conformational modifications during the straightening procedure. SEM analyses showed the effectiveness of the treatment at the cuticular level.
authors: Department of Industrial Chemistry "Toso Montanari", Alma Mater Studiorum- University of Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy.
authors: C
authors: C
authors: Boga
authors: P
authors: P
authors: Taddei
authors: G
authors: G
authors: Micheletti
authors: F
authors: F
authors: Ascari
authors: B
authors: B
authors: Ballarin
authors: M
authors: M
authors: Morigi
authors: S
authors: S
authors: Galli
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D005557:Formaldehyde; D006038:Glyoxylates; D006203:Hair Preparations; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D000447:Aldehydes; D000596:Amino Acids; D006038:Glyoxylates; D006203:Hair Preparations; D005557:Formaldehyde; C031150:glyoxylic acid
keywords: chemical synthesis; glyoxylic acid; hair treatment; keratin; spectroscopy; straightening