A comprehensive review of matcha: production, food application, potential health benefits, and gastrointestinal fate of main phenolics.

Matcha, a powder processed from tea leaves, has a unique green tea flavor and appealing color, in addition to many other sought after functional properties for a wide range of formulated food applications (e.g., dairy products, bakery products, and beverage). The properties of matcha are influenced by cultivation method and processing post-harvest. The transition from drinking tea infusion to eating whole leaves provides a healthy option for the delivery of functional component and tea phenolics in various food matrix. The aim of this review is to describe the physico-chemical properties of matcha, the specific requirements for tea cultivation and industrial processing. The quality of matcha mainly depends on the quality of fresh tea leaves, which is affected by preharvest factors including tea cultivar, shading treatment, and fertilization. Shading is the key measure to increase greenness, reduce bitterness and astringency, and enhance umami taste of matcha. The potential health benefits of matcha and the gastrointestinal fate of main phenolics in matcha are covered. The chemical compositions and bioactivities of fiber-bound phenolics in matcha and other plant materials are discussed. The fiber-bound phenolics are considered promising components which endow matcha with boosted bioavailability of phenolics and health benefits through modulating gut microbiota.

Roasting process shaping the chemical profile of roasted green tea and the association with aroma features.

Roasting process impacts the chemical profile and aroma of roasted tea. To compare the impacts of far-infrared irradiation and drum roasting treatments (light, medium and heavy degrees), the corresponding roasted teas were prepared from steamed green tea for chemical analyses and quantitative descriptive analysis on aroma, and correlations between volatiles and aroma attributes were studied. There were 8 catechins, 13 flavonol glycosides and 105 volatiles quantified. Under heavy roasting treatments, most catechins and flavonol glycosides decreased, and aldehydes, ketones, furans, pyrroles/pyrazines, and miscellaneous greatly increased, while far-infrared irradiated teas had distinct nutty aroma compared with the roasty and burnt odor of drum roasted teas. The weighted correlation network analysis result showed that 56 volatiles were closely correlated with the aroma attributes of roasted teas. This study reveals the differential chemical and sensory changes of roasted teas caused by different roasting processes, and provides a novel way for flavor chemistry study.

Utilization of albumin fraction from defatted rice bran to stabilize and deliver (-)-epigallocatechin gallate.

This work aims to use defatted rice bran albumin (RBA) for delivering epigallocatechin gallate (EGCg). The mode of RBA particle size shifted from 142 nm to 164 nm upon interaction with EGCg. Hydrophobic interaction is the major force between EGCg and RBA resulted in the formation of EGCg-RBA complex based on fluorescence quenching. Upon incorporation into RBA, the recovery of EGCg in pH 7.4 phosphate buffer was elevated by 2 folds. The recovery of EGCg in EGCg-RBA was 18.9% after 2 h intestinal digestion, being higher than 7.6% of native EGCg. The pretreatments of HT-29 cells with EGCg, RBA and EGCg-RBA significantly repressed the transcriptional activation of mitogen-activated protein kinase 14, nuclear transcription factor-κB, and activators of transcription 3 as stimulated with interleukin-1ß afterwards, leading to attenuated expressions of corresponding downstream genes. Antioxidant ability importantly functioned in anti-inflammation. RBA is a promising vehicle with inherent anti-inflammatory property for stabilizing and delivering EGCg.

MicroRNA-219 decreases hippocampal long-term potentiation inhibition and hippocampal neuronal cell apoptosis in type 2 diabetes mellitus mice by suppressing the NMDAR signaling pathway.

OBJECTIVE: Type 2 diabetes mellitus (T2DM) is a complex polygenic disease that causes hyperglycemia and accounts for 90%-95% of all diabetes mellitus cases. Hence, this study aimed to examine the effects of microRNA-219 (miR-219) on inhibition of long-term potentiation (LTP) and apoptosis of hippocampal neuronal cells in T2DM mice through the N-methyl-d-aspartate receptor (NMDAR) signaling pathway regulation. METHODS: The T2DM mouse models were established, after which LTP in vivo was recorded by means of electrical biology, and the fasting blood glucose of mice was measured. Next, the density of pyramidal neurons in each group was calculated. Additionally, the expression levels of miR-219, the NMDAR signaling pathway [NMDAR1 (NR) 1, NR2A, and NR2B), downstream target proteins [calmodulin-dependent protein kinase-II (CaMK-II) and cAMP response element binding protein (CREB)], and apoptosis-related factors [Bcl2-associated X protein (Bax), c-caspase-9 and c-caspase-3] in the hippocampal tissues were determined. Finally, immunohistochemistry was applied to detect and measure the positive expression of Bax, caspase-9, and caspase-3 proteins. RESULTS: The results showed that upregulation of miR-219 increases LTP and density of pyramidal neurons in the hippocampal tissues of mice, while it decreases blood glucose of db/db mice. In addition, miR-219 upregulation also leads to decreased mRNA levels of NR1, NR2A, NR2B, CaMK-II, and CREB and protein levels of NR1, NR2A, NR2B, CaMK-II, CREB, p-CREB, Bax, c-caspase-9, and c-caspase-3. Furthermore, upregulation of miR-219 inhibits positive expression of Bax, caspase-9, and caspase-3 proteins, leading to the suppression of hippocampal neuronal cell apoptosis. CONCLUSION: The findings from this study indicated that the upregulation of miR-219 decreases LTP inhibition and hippocampal neuronal cell apoptosis in T2DM mice by downregulating the NMDAR signaling pathway, therefore suggesting that MiR-219 might be a future therapeutic strategy for T2DM.

Preparation of tea catechins using polyamide.

An adsorption separation method using Polyamide-6 (PA) as an adsorbent was developed to separate catechins from green tea extract. The adsorption capacity of total catechins for PA was 193.128 mg g⁻¹ with an adsorption selectivity coefficient K(A)(B) of total catechins over caffeine 21.717, which was better than macroporous resin model HPD 600. The Langmuir model and the pseudo-second order mode were primely fitted to describe its equilibrium data and adsorption kinetics, respectively. PA column separation by two-step elution using water and 80% (v/v) aqueous ethanol was established to prepare catechins complex which contained 670.808 mg g⁻¹ total catechins and 1.828 mg g⁻¹ caffeine. It is considered that PA was a promising adsorbent for selective isolation of catechins.