Determination of Soyasaponins I and βg in Raw and Cooked Legumes by Solid Phase Extraction (SPE) Coupled to Liquid Chromatography (LC)–Mass Spectrometry (MS) and Assessment of Their Bioaccessibility by an in Vitro Digestion Model

Legumes contain a rich variety of phytochemicals as soyasaponins, triterpenoidal glycosides that possess multiple health-promoting properties, such as lowering of cholesterol. In this work, the quantification of soyasaponins I and βg in 60 raw and cooked legumes by using a solid phase extraction (SPE) coupled to a liquid chromatography (LC)–mass spectrometry (MS) method was carried out. Results showed that lentils are a good source of soyasaponins, with a content of soyasaponin I that ranged from 636 to 735 mg kg–1 and of soyasaponin βg from 672 to 1807 mg kg–1. The cooking process produced a small loss of soyasaponins in water, that is, 4.8–8.7%, and partially converted soyasaponin βg into soyasaponin I. In addition, the bioaccessibility of soyasaponins I in lentils was studied; the values ranged from 8.9 ± 0.3 to 10.6 ± 1.1% in the duodenal compartment. On the basis of these results, soyasaponins could be effective in lowering exogenous cholesterol.