title: Chitosan does not inhibit enzymatic action of human pancreatic lipase in Langmuir monolayers of 1,2-didecanoyl-glycerol (DDG).
abstract: In this study, we tested the hypothesis according to which chitosan reduces lipid digestion by blocking the access of lipases to ingested fat. Because lipase action takes place mostly at interfaces, we produced Langmuir films of 1,2-didecanoyl-glycerol (DDG), which is the substrate for human pancreatic lipase (HPL). The experimental assays were carried out in acidic medium, at pH 3.0, to ensure that chitosan is completely soluble. Chitosan was found to affect strongly the surface activity of HPL that forms a Gibbs monolayer at the air/water interface, but did not inhibit the enzymatic action of HPL toward the DDG monolayer. The latter was observed using two surface-specific spectroscopic techniques, namely polarization-modulated infrared reflection-absorption and sum-frequency generation (SFG). The extension of DDG hydrolysis calculated using SFG spectroscopy was 33% in the absence of chitosan, and ranged from 29 to 50% in the presence of chitosan at concentrations of 0.20 g L(-1) and 0.30 g L(-1), respectively. Therefore, fat "protection" by chitosan is unlikely to be an important factor in fat reduction.
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil. Electronic address: adriano_lsouza@yahoo.com.br.
authors.forename: Adriano L
authors.initials: AL
authors.lastname: Souza
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil.
authors.forename: Felippe J
authors.initials: FJ
authors.lastname: Pavinatto
authors.affiliation: Institute for Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo (UNIFESP), Diadema, SP 09972-270, Brazil.
authors.forename: Luciano
authors.initials: L
authors.lastname: Caseli
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil.
authors.forename: Diogo
authors.initials: D
authors.lastname: Volpati
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil.
authors.forename: Paulo B
authors.initials: PB
authors.lastname: Miranda
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil.
authors.forename: Osvaldo N
authors.initials: ON
authors.lastname: Oliveira
mesh_terms: D048271:Chitosan / Q000009:adverse effects*; D004075:Diglycerides / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008049:Lipase / Q000378:metabolism*
chemical_list: D004075:Diglycerides; C044297:1,2-didecanoylglycerol; D048271:Chitosan; D008049:Lipase; C518354:PNLIP protein, human
keywords: Chitosan; Fat reduction; Human pancreatic lipase; Langmuir monolayers; Sum-frequency generation spectroscopy