Theabrownin (TB), a distinctive pigment derived from Pu-erh tea, is garnering increasing attention for its potential health benefits. This article delves into the effects of theabrownin on various aspects of health, including its impact on innate immunity, inflammation, and overall well-being, while also exploring its primary food source: Pu-erh tea.
What is Theabrownin?
Theabrownin (TB) is a dark-brown complicated product that forms during the solid-state fermentation of sun-dried green tea to produce ripened Pu-erh tea. The numerous polyphenols in the tea undergo microbial oxidation and polymerization and are complexed with polysaccharides, theanine, theophylline, and other compounds in the tea to form theabrownin (10-12%). It not only determines the flavor of Pu-erh tea, but also its physiological activity.
Theabrownin and Innate Immunity
Innate immunity, the body's first line of defense against pathogens, can be significantly influenced by theabrownin. Studies using RAW264.7 macrophages, a type of immune cell, have revealed that TB promotes their proliferation, alters their morphology, and enhances their pinocytic and phagocytic abilities. These processes are crucial for the immune system to recognize and eliminate foreign invaders.
Enhanced Immune Response
Theabrownin significantly increases the secretion of nitric oxide (NO) and cytokines by RAW264.7 macrophages, further enhancing the immune response. Cytokines are signaling molecules that help regulate immunity and inflammation, while nitric oxide plays a vital role in killing pathogens.
Modulation of Inflammation
Interestingly, TB inhibits the release of inflammatory signals in RAW264.7 macrophages primed with lipopolysaccharide (LPS), implying that TB modulates the excessive inflammation induced by bacterial infection. This suggests that theabrownin may have a regulatory effect, preventing an overactive immune response that can lead to tissue damage.
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Activation of Signaling Pathways
A Western blot showed that TB could activate the toll-like receptor (TLR)2/4-mediated myeloid differentiation factor 88 (MyD88)-dependent mitogen activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathway and the TLR2-mediated phosphoinositide 3-kinase (PI3K)-AKT signaling pathway, enhancing the immune functions of RAW264.7 macrophages. TB also inhibited the phosphorylation of core proteins in the MAPK/NF-κB/PI3K-AKT signaling pathway induced by LPS. These pathways are critical for immune cell activation and cytokine production. Theabrownin's ability to modulate these pathways suggests a targeted approach to enhancing immunity.
Transcriptomic Analysis
Transcriptome analysis of RAW264.7 macrophages revealed that TB modulates the toll-like receptor signal pathway. A gene ontology (GO) enrichment analysis indicated that TB treatment strongly modulated the immune response and inflammation.
Theabrownin and Cholesterol Levels
Studies have shown that fermented Pu-erh tea has a better blood lipid lowering and anti-atherosclerotic effect than raw tea. Theabrownin a key active substance of fermented tea, exhibits various biological properties providing health benefits against atherosclerosis, diabetes, and allergic reactions.
Impact on Bile Acid Metabolism
Theabrownin suppresses the bile salt hydrolase (BSH) related microbes and BSH activity. Reduced BSH activity results in increased ileal conjugated BAs which further inhibit the intestinal FXR-FGF15/19 signaling pathway to elevate hepatic BA production.
Effects on Gut Microbiota
Theabrownin reshaped the gut microbiota in mice and human. Pu-erh tea reduced the abundance of BSH microbes and BSH activity.
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Theabrownin and Egg Quality
Dietary theabrownin supplementation can have positive effects on laying hens. The addition of 100 mg/kg theabrownin in the diet could improve performance and egg quality, and extend the shelf life of eggs. On the other hand, the addition of theabrownin increased the antioxidant capacity of the ovary and the magnum and improved intestinal health.
Improved Production Performance and Egg Quality
TB (extracted from Pu-erh tea) dietary supplementation at 100 mg/kg markedly increased the laying rate, egg weight, and feed conversion efficiency in laying hens. We also observed that 100-400 mg/kg TB increased the albumen quality (higher albumen height and Haugh unit) in fresh and stored eggs for up to 21 days.
Enhanced Antioxidant Capacity
TB supplementation decreased MDA and 8-OHDG levels while increasing the SOD, GSH, and CAT levels, thereby improving the antioxidant status of the magnum.
Intestinal Health
TB supplementation can increase intestinal health by promoting the levels of mucus barrier-associated proteins.
Food Sources of Theabrownin
The primary food source of theabrownin is Pu-erh tea, a unique type of fermented tea produced exclusively in Yunnan Province, China.
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Pu-erh Tea Production
Pu-erh tea is exclusively produced from the fresh leaves and buds of the large-leaf tea plant species Camellia sinensis var. Assamica. Pu-erh tea has been consumed for more than 1800 years and is divided into raw and ripened tea. Raw Pu-erh tea is not fermented. However, ripened Pu-erh tea is made by carrying out the solid-state fermentation of sun-dried green tea. During the fermentation process, the catechins and their gallate derivatives are oxidized to complex phenolic tea pigments including theaflavins (TF), thearubigins (TR) and, theabrownins (TB).
Extraction of Theabrownin
TB was extracted according to a previously described method, and the yield was 10.56%. Briefly, Pu-erh tea powder (3500 g) was suspended into a tenfold volume of absolute ethyl alcohol, mixed for twelve hours, and then vacuum-strained. The residuum was leached with a tenfold volume of boiled distilled water, retained at 83 °C for 20 min with unremitting stirring, and then vacuum-strained. Repeating the same extraction method three times, the extracts were combined, and then the volume was decreased to one-fifth through vacuum evaporation. A series of liquid-liquid extraction processes were adopted to extract the concentrated solution that was obtained before, involving the same volume of extraction with chloroform, ethyl acetate, and n-butanol, two, three, and four times, respectively. The complete volume of the water for layers was evaporated to one-quarter, and then absolute ethyl alcohol was added to a final proportion of 83.1% to immerse the TB coarse extracts.
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