Triterpenoid Saponins in Oat Bran and Their Levels in Commercial Oat Products

Oats are commonly consumed as whole grains and generally considered as a healthy food. However, the bioactive compounds in oats have not been fully investigated. In this study, we reported for the first time the purification, structure elucidation, and chemical profile of the major triterpenoid saponins in oat bran as well as the quantification of the major triterpenoid saponins in commercial oat products. Thirteen triterpenoid saponins (1-13) were purified from oat bran. Their structures were characterized by analyzing their high-resolution mass spectrometry (MS), one-dimensional (1-D), and two-dimensional (2-D) NMR spectra. All of the purified triterpenoid saponins have been reported from oat bran for the first time, in which compounds (1-8) are newly discovered compounds and compound (9) is a new natural product. Using ultra-high-performance liquid chromatography with tandem mass spectrometry techniques, a complete profile of oat triterpenoid saponins was established, and the contents of the 13 purified triterpenoid saponins were quantitated in 19 different commercial oat products. The total levels of the 13 triterpenoid saponins varied from 1.77 to 18.20 mu g/g in these 19 products, in which oat bran (11 samples) and oatmeal (three samples) had higher levels than cold oat cereal (five samples). Among the 11 commercial oat bran samples, the average total levels of the 13 triterpenoid saponins in the five sprouted oat samples are slightly higher than those in the regular oat bran products.