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Determination of Melatonin in Rice (Oryza sativa) Grains by Pressurized Liquid Extraction
- Setyaningsih, Widiastuti, Saputro, Irfan Estiono, Barbero, Gerardo FernÃ¡ndez, Palma, Miguel, Garcia Barroso, Carmelo
- Journal of agricultural and food chemistry 2015 v.63 no.4 pp. 1107-1115
- Oryza sativa, detection limit, ethyl acetate, fluorescence, high performance liquid chromatography, human health, melatonin, methanol, parboiling, red rice, whole grain foods
- 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 2IV7â2 fractional factorial design. The optimum extraction conditions were achieved by applying 70% EtOAc in MeOH at 200 Â°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 Î¼g kg â1), and the highest levels were found in red rice.