Teratogenic effect evaluation of Monascus red oral exposure to pregnant rats and their gut microbiota

Monascus red (MR) is widely used as a natural food colorant and preservative in East Asia. However, the potential effects of MR during pregnancy remains unknown. In this study, MR was administrated to Sprague-Dawley (SD) rats at doses of 0, 0.50, 1.58, and 5.00 g/kg bw on gestational days 6–15 by oral gavage. In the maternal and embryo-fetal examinations, there were no marked toxicities in terms of general clinical signs, body weight, food consumption, serum endocrine indices, organ weights, thyroid histopathology, examinations of uterine contents and fetuses. In the gut microbiota analysis, the 5.00 g/kg bw dose of MR decreased the α diversity and slightly changed their community structure at the genus level. Yet no marked toxicities in maternal animals or embryo-fetal development were observed. The no-observed-adverse-effect-level (NOAEL) of the maternal and developmental toxicity through oral exposure to MR was 5.00 g/kg bw, the highest dose tested in rats.