Trapping Acrolein by Theophylline/Caffeine and Their Metabolites from Green Tea and Coffee in Mice and Humans

Theanine Capture of Reactive Carbonyl Species in Humans after Consuming Theanine Capsules or Green Tea

Acrolein (ACR), methylglyoxal (MGO), and glyoxal (GO) are a class of reactive carbonyl species (RCS), which play a crucial role in the pathogenesis of chronic and age-related diseases. Here, we explored a new RCS inhibitor (theanine, THE) and investigated its capture capacity on RCS in vivo by human experiments. After proving that theanine could efficiently capture ACR instead of MGO/GO by forming adducts under simulated physiological conditions, we further detected the ACR/MGO/GO adducts of theanine in the human urine samples after consumption of theanine capsules (200 and 400 mg) or green tea (4 cups, containing 200 mg of theanine) by using ultraperformance liquid chromatography-time-of-flight-high-resolution mass spectrometry. Quantitative assays revealed that THE-ACR, THE-2ACR-1, THE-MGO, and THE-GO were formed in a dose-dependent manner in the theanine capsule groups; the maximum value of the adducts of theanine was also tested. Furthermore, besides the RCS adducts of theanine, the RCS adducts of catechins could also be detected in the drinking tea group. Whereas, metabolite profile analysis showed that theanine could better capture RCS produced in the renal metabolic pathway than catechins. Our findings indicated that theanine could reduce RCS in the body in two ways: as a pure component or contained in tea leaves.

Scavenging Glyoxal and Methylglyoxal by Synephrine and Neohesperidin from Flowers of Citrus aurantium L. var. amara Engl. in Mice and Humans

There is considerable research evidence that α-dicarbonyl compounds, including glyoxal (GO) and methylglyoxal (MGO), are closely related to many chronic diseases. In this work, after comparison of the capture capacity, reaction pathway, and reaction rate of synephrine (SYN) and neohesperidin (NEO) on GO/MGO in vitro, experimental mice were administrated with SYN and NEO alone and in combination. Quantitative data from UHPLC-QQQ-MS/MS revealed that SYN/NEO/HES (hesperetin, the metabolite of NEO) could form the GO/MGO-adducts in mice (except SYN-MGO), and the levels of GO/MGO-adducts in mouse urine and fecal samples were dose-dependent. Moreover, SYN and NEO had a synergistic scavenging effect on GO in vivo by promoting each other to form more GO adducts, while SYN could promote NEO to form more MGO-adducts, although it could not form MGO-adducts. Additionally, human experiments showed that the GO/MGO-adducts of SYN/NEO/HES found in mice were also detected in human urine and fecal samples after drinking flowers of Citrus aurantium L. var. amara Engl. (FCAVA) tea using UHPLC-QTOF-MS/MS. These findings provide a novel strategy to reduce endogenous GO/MGO via the consumption of dietary FCAVA rich in SYN and NEO.

Theanine in Tea: An Effective Scavenger of Single or Multiple Reactive Carbonyl Species at the Same Time

Reactive carbonyl species (RCS) are generated during thermal food processing, and their accumulation in the body increases the risk of various chronic diseases. Herein, the RCS-scavenging ability of theanine, a unique nonproteinogenic amino acid, was evaluated in terms of the scavenging rate, reaction kinetics, and reaction pathway using LC-MS/MS. Three major products of theanine conjugated with acrolein (ACR) and glyoxal (GO) were prepared and identified using nuclear magnetic resonance. Thereafter, the simultaneous reactions of four types of RCS (namely, ACR, crotonaldehyde, methylglyoxal, and GO) with theanine were discussed in RCS-theanine and RCS-tea models. Under different reaction ratios, theanine could nonspecifically scavenge the four coexisting RCS by forming adducts with them. The amount of theanine-RCS adducts in green and black tea was more than that of catechin (epigallocatechin gallate, epigallocatechin, epicatechin gallate, and epicatechin)-RCS adducts despite the lower content of theanine than catechins. Thus, theanine, as a food additive and dietary supplement, could demonstrate new bioactivity as a promising RCS scavenger in food processing.

Origin and Fate of Acrolein in Foods

Acrolein is a highly toxic agent that may promote the occurrence and development of various diseases. Acrolein is pervasive in all kinds of foods, and dietary intake is one of the main routes of human exposure to acrolein. Considering that acrolein is substantially eliminated after its formation during food processing and re-exposed in the human body after ingestion and metabolism, the origin and fate of acrolein must be traced in food. Focusing on molecular mechanisms, this review introduces the formation of acrolein in food and summarises both in vitro and in vivo fates of acrolein based on its interactions with small molecules and biomacromolecules. Future investigation of acrolein from different perspectives is also discussed.

Interconversion and Acrolein-Trapping Capacity of Cardamonin/Alpinetin and Their Metabolites In Vitro and In Vivo

People are at high risk of exposure to endogenous and exogenous acrolein (ACR). ACR can cause a multitude of illnesses, including cardiovascular disease, Alzheimer's disease, and diabetes. In this study, we investigated the reaction pathway of cardamonin (CAR) or alpinetin (ALP) with ACR and the interconversion of CAR and ALP in vitro at 37 °C in phosphate-buffered saline using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Subsequently, ACR adducts of CAR, ALP, and their metabolites, for example, CAR-ACR-1, ALP-ACR, mono-ACR-pinocembrin chalcone (PIN-ACR), and mono- and di-ACR-naringenin (NAR-ACR and NAR-2ACR), were detected in urine samples, but only CAR-ACR-1 and ALP-ACR were detected in fecal samples from the CAR- and ALP-treated mouse groups using ultraperformance liquid chromatography-MS/MS, respectively. Quantitative analyses showed that CAR, ALP, and their metabolites markedly scavenged ACR in a dose-dependent manner in vivo. Furthermore, we also found that the metabolites of CAR or ALP remained and promoted the ACR-trapping ability.