Metabolomics analysis of health-care functional substances in Zaohongnuo

Zaohongnuo is a folk specialty rice in Dongguan, Guangdong. It is used to boil water for drinking to remove the accumulated moisture in the human body and maintain health. In order to explore the mechanism of removing moisture and maintaining health of Zaohongnuo, the appearance phenotypes of rice and brown rice of two kinds of red glutinous rice were observed, with the common red glutinous rice Hanghongnuo No.1 as the control. The metabolome of rice and brown rice of Hanghongnuo No.1 and Zaohongnuo was determined. The principal component analysis (PCA), sample correlation analysis and metabolite relative content heat map showed that the sequencing results were highly reliable. A total of 1563 metabolites were identified in Zaohongnuo, of which 1178 were successfully classified. The 63 differential metabolites among rice varieties and the 56 differential metabolites among brown rice varieties could be both clustered into three major groups, and the enriched types of differential metabolites were flavonoid glycosides, carbohydrates and their conjugates. The higher content of the medicinal ingredients silibinin, esculin and cholestenone in Zaohongnuo has a targeted therapeutic effect on the clinical manifestations of dampness syndrome such as liver fire inflammation, short urination, chest tightness and irritability. The differential metabolites between rice and brown rice were enriched in three KEGG pathways: ‘galactose metabolism’, ‘neomycin, kanamycin and gentamicin biosynthesis’ and ‘starch and sucrose metabolism’. This study showed that Zaohongnuo contains rich dampness-removing and health-care functional substances, laying a theoretical foundation for the health-care application of Zaohongnuo in industry.