title: Determination of Melatonin in Rice (Oryza sativa) Grains by Pressurized Liquid Extraction.
abstract: Melatonin provides a number of benefits for human health. The study reported here concerns the optimization, validation, and application of analytical pressurized liquid extraction and high-performance liquid chromatography coupled to a fluorescence detector for the determination of melatonin in rice grains. The factors that are most likely to affect the extraction efficiency were optimized with a 2IV7-2fractional factorial design. The optimum extraction conditions were achieved by applying 70% EtOAc in MeOH at 200 °C and 200 atm for a static time of 5 min in two cycles with 50% flushing and a 60 s purge to extract a 2.5 g rice sample. The method validation ensured excellent linearity, limit of detection, limit of quantification, precision, and recovery. Furthermore, the method was applied to various rice products composed of polished, whole grain, aromatic, black, black glutinous, red, and parboiled rice. All kinds of pigmented rice grains showed high levels of melatonin (>100 μg kg-1), and the highest levels were found in red rice.
authors.affiliation: Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Gadjah Mada University , Jalan Flora 55281, Yogyakarta, Indonesia.|Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz , Campus de Excelencia Internacional Agroalimentario (CeiA3), Campus del Rio San Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: Widiastuti
authors.initials: W
authors.lastname: Setyaningsih
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz , Campus de Excelencia Internacional Agroalimentario (CeiA3), Campus del Rio San Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: Irfan Estiono
authors.initials: IE
authors.lastname: Saputro
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz , Campus de Excelencia Internacional Agroalimentario (CeiA3), Campus del Rio San Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: Gerardo Fernández
authors.initials: GF
authors.lastname: Barbero
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz , Campus de Excelencia Internacional Agroalimentario (CeiA3), Campus del Rio San Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Palma
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz , Campus de Excelencia Internacional Agroalimentario (CeiA3), Campus del Rio San Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: Carmelo
authors.initials: C
authors.lastname: García Barroso
keywords: HPLC-FD; melatonin; pressurized liquid extraction; rice grains