Surfactant and antioxidant properties of an extract from Chenopodium quinoa Willd seed coats

Chenopodium quinoa Willd (quinoa) has been a source of food for millennia by the Andes region native population. Because of its bitter taste, quinoa seeds are commercialized without their coat for human consumption. Quinoa coats are surfactant sub-products of the quinoa food industry, which have been only characterized to contain triterpene saponins. We postulated that this coat should also contain antioxidant molecules as part of the defense system of the quinoa seed. We found that a quinoa seed coats hydroalcoholic extract, displayed thiol compounds in addition to polyphenols, recognized antioxidants. Accordingly, it inhibited microsomal lipid peroxidation and the loss of microsomal thiol content, both oxidative phenomena promoted by Cu²⁺/ascorbate. Microsomal glutathione S-transferase (GST) is inhibited by reducing agents, which decrease the content of catalytically active disulfide-linked dimers. The effects of this quinoa extract on microsomal GST are consistent with it displaying disulfide reducing properties. The occurrence of thiol compounds in this quinoa extract is discussed in terms of the potential of their antioxidant properties.