Comparative analysis of minerals, carotenoids, and tocochromanols in ripe seeds, immature seeds and tepals of bitter and non-bitter quinoa genotypes

Abstract

Quinoa (Chenopodium quinoa Willd.) contains high amounts of minerals, carotenoids and vitamin E (tocochromanols), but also antinutrients, such as saponins. Based on their saponin content, quinoa can be classified into “bitter” and “non-bitter” genotypes. Carotenoids (lutein, zeaxanthin, β-carotene, β-cryptoxanthin), vitamin E and saponins share a precursor in their respective biosynthesis pathways. Thus, we investigated whether the downregulation of saponin biosynthesis in non-bitter quinoa affects the contents of minerals and lipid-soluble compounds compared to bitter quinoa. The analytes were quantified in ripe seeds of fifty (23 bitter and 27 non-bitter) quinoa genotypes. A subset of twelve genotypes (6 bitter and 6 non-bitter) was analyzed for carotenoids and tocochromanols in immature seeds and their tepals. Total mineral (8206 mg/kg vs. 8646 mg/kg) and carotenoid contents (314 µg/100 g vs. 242 µg/100 g) did not differ between bitter and non-bitter ripe seeds. However, non-bitter quinoa seeds contained higher lutein and total tocochromanol (driven by tocotrienols) contents than bitter genotypes. Carotenoid and tocochromanol contents in immature seeds and tepals did not differ between phenotypes; tepals had up to 74-fold higher contents than the seeds. In conclusion, the downregulation of saponin biosynthesis in non-bitter quinoa genotypes does not affect the biosynthesis of carotenoids and tocochromanols.