Characterization of brewer's spent grain extracts by tandem mass spectrometry and HPLC‐DAD: Ferulic acid dehydrodimers, phenolamides, and oxylipins

Abstract

Brewer's spent grain (BSG) is a major by‐product of the brewing industry which is generated in high amounts. In recent years, sustainable food production has become more and more important. BSG mainly used as cattle feed has gained high interest due to not only its valuable ingredients such as fiber and proteins but also secondary metabolites remaining in BSG after the brewing process and known for many biological effects. In the present study, various methods were applied, such as acetone extraction (A), alkaline hydrolysis followed by ethyl acetate extraction (HE), and acetone extraction of alkaline hydrolysis residue (HA). Compounds present in the respective bioactive extracts were characterized by mass spectrometry to identify the active compounds. Various hydroxycinnamic acid derivatives as well as oxylipins and some dicarboxylic acids, such as azelaic acid, were present in HE and HA extracts. In contrast, some catechins and phenolamides, such as numerous hordatines, as well as oxylipins and phospholipids were detected in A extracts. Quantification using HPLC‐DAD revealed hordatine contents up to 172.2 ± 2.1 μg p‐ coumaric acid equivalents/mg extract. Hydroxycinnamic acid derivatives content accounted for up to 48% of the total extract (HE extracts) but only around 3% of the total HA extracts. In summary, all extracts contained secondary plant metabolites belonging to different classes, ranging from hydroxycinnamic acids to phenolamides, such as not only hordatines but also oxylipins, which were identified for the first time in BSG.

New Insights into Identification, Distribution, and Health Benefits of Polyamines and Their Derivatives

“…CPAs have been reported to be widely present in the Poaceae and Solanaceae families, such as barley, wheat, rice, maize, potato, tomato, Lycium berry, bee pollen, and their related food products (Table ). − So far, about 80 different types of CPAs have been identified in edible plants (Table ), including 12 conjugated putrescine, 2 conjugated cadaverine, 39 conjugated spermidine, 20 conjugated spermine, and 8 conjugated agmatine. Notably, bee pollen is evidenced to possess abundant CPAs; ,,, for example, the 31 CPAs and their 33 cis–trans isomers were observed in 20 types of monofloral bee pollen, constituting nearly half of the total identified CPAs in foods .…”