Preliminary Toxicology Research Of Pu-erh Tea

1. BackgroundPu-erh tea is a kind of special tea of China, which prepared by fermentating of crude green tea leaves, having strong effects in protecting from decayed teeth, lipid peroxidation, hypercholesterolemia, obesity, aging and cancers. In recent decades, Pu-erh tea are popular with people around the world because of it's unique flavor and gradually recognized benefits of people, and noticed by more and more scholars all over the world.As the hot sale of Pu-erh tea, many manufacturers began to produce Pu-erh tea, confused the Pu-erh tea market. Risk analysis and safety evaluation is needed in establishing standards of food hygiene according to the World Trade Organization (WTO) requirements and the relevant agreements of Codex Alimentarius Commission (CAC). Therefore, effective evaluation of Pu-erh tea including components analysis and toxicological experiment is necessary to ensure the export.The weak toxicity of polyphenols, caffeine and other ingredients had been reported. A series of fermentation process involved micro-organisms in the process of Pu-erh tea also increased complexity and difficulty of identification of metabolites and composition. In addition, the relationship of its storage and security needs further study.2. ObjectCompared the acute toxicity of green tea, Pu-erh green tea extract (GTE) and Pu-erh black tea extract (BTE). Explore the acute and subacute toxicity induceded by Pu-erh tea, with a view to provide a basis for further study. Study its toxicologic effects associating with the difference of components. 3. MethodOur study including 3 parts: Part 1 Analysis of the chemical components of GTE and BTE, Part 2 Acute toxic experiment, Part 3 Subacute toxic experiment. 3.1 Determination of componentsThe tea was prepared with methods in accordance with national and local standards of Yunnan, conventional components were determined with corresponding methods, the chemical components of green tea, Pu-erh green tea extract (GTE) and Pu-erh black tea extract (BTE) were compared by high performance liquid chromatography (HPLC). 3.2 Acute toxic experimentThree batches of Kunming mice were obtain for three different samples of tea, each batch of 40, a total of 120. Each batch of animals was randomly divided into five groups, treated with: green tea 10.9 g/kg, 9.0 g/kg, 7.4 g/kg, 6.1 g/kg, 5.0 g/kg; GTE 14.1 g/kg, 10.9 g/kg, 8.4 g/kg, 6.5 g/kg, 5.0 g/kg; BTE 20.0 g/kg, 14.1 g/kg, 10.0g/kg, 7.1 g/kg, 5.0 g/kg, respectively. Sign of poisoning and death were observed for 14 days. LD50 was calculated in the end of experiment duration.3.3 Subacute toxic experimentSingle subacute tea extract doses of 0, 1250, 2500, and 5000 mg/kg dissolved in distilled water were administered by oral gavage for 28 days. The major toxicological endpoints examined including animal body weight, selected tissue weights, hematological and serum biochemical examination and histopathological examinations.4. Results4.1 Determination of componentsCatechins, theogallin, and caffeine were detected in GTE (21.945%, 3.295% and 3.037%, respectively). However, BTE contains only a scarce amount of catechins and the level of caffeine (2.580%) was lower as compared to GTE, but gallic acid (0.626%) was separated from BTE. Theogallin was extracted the first time. 4.2 Acute toxic experimentThe LD50 of Qu Ming green tea, Pu-erh green tea and Pu-erh black tea is: 10.38 g/kg, 11.99 g/kg, 18.34 g/kg, respectively. 4.3 Subacute toxic experimentThe body weights of all GTE treated males and BTE groups were statistically significant lower than controls, and some serum biochemical data including alanine aminotransferase (ALT) and creatinine (Cre) were increased in 5000 mg/kg/day GTE groups. Liver had slight histopathological change in GTE 5000 mg/kg/day and BTE mg/kg/day. Besides, no other adverse effects in food consumption, body weight, clinical chemistry, haematology, gross pathology and histopathology were observed with a 28-day subacute study of GTE and BTE in male and female rats.5. ConclutionOur results shows that, BTE and GTE is assessed as of no toxicity according with the toxicity grading standards publiced by WHO in 1977. The no observed adverse effect level (NOAEL) for systemic toxicity after oral administration was preliminary concluded as 2500 mg/kg/day for GTE and 5000 mg/kg/day for BTE under the conditions of this study. The probable target organs of GTE were liver and kidney. It seems that low levels of caffeine and catechins in Pu-erh black tea which fermented by fungi lead to a low toxicity in vivo.