Bibliografia____________________________________

(1) Li J, Zeng L, Liao Y, Gu D, Tang J, Yang Z. Influence of Chloroplast Defects on Formation of Jasmonic Acid and Characteristic Aroma Compounds in Tea (Camellia sinensis) Leaves Exposed to Postharvest Stresses. Int J Mol Sci. 2019 Feb 27;20(5):1044. doi: 10.3390/ijms20051044. 

Abstract. Characteristic aroma formation in tea (Camellia sinensis) leaves during the oolong tea manufacturing process might result from the defense responses of tea leaves against these various stresses, which involves upregulation of the upstream signal phytohormones related to leaf chloroplasts, such as jasmonic acid (JA). Whether chloroplast changes affect the formation of JA and characteristic aroma compounds in tea leaves exposed to stresses is unknown. In tea germplasms, albino-induced yellow tea leaves have defects in chloroplast ultrastructure and composition. Herein, we have compared the differential responses of phytohormone and characteristic aroma compound formation in normal green and albino-induced yellow tea leaves exposed to continuous wounding stress, which is the main stress in oolong tea manufacture. In contrast to single wounding stress (from picking, as a control), continuous wounding stress can upregulate the expression of CsMYC2, a key transcription factor of JA signaling, and activate the synthesis of JA and characteristic aroma compounds in both normal tea leaves (normal chloroplasts) and albino tea leaves (chloroplast defects). Chloroplast defects had no significant effect on the expression levels of CsMYC2 and JA synthesis-related genes in response to continuous wounding stress, but reduced the increase in JA content in response to continuous wounding stress. Furthermore, chloroplast defects reduced the increase in volatile fatty acid derivatives, including jasmine lactone and green leaf volatile contents, in response to continuous wounding stress. Overall, the formation of metabolites derived from fatty acids, such as JA, jasmine lactone, and green leaf volatiles in tea leaves, in response to continuous wounding stress, was affected by chloroplast defects. This information will improve understanding of the relationship of the stress responses of JA and aroma compound formation with chloroplast changes in tea.

(2) Yang CS, Zhang J. Studies on the Prevention of Cancer and Cardiometabolic Diseases by Tea: Issues on Mechanisms, Effective Doses, and Toxicities. Agric Food Chem. 2019 May 15;67(19):5446-5456. doi: 10.1021/acs.jafc.8b05242.

Abstract. This article presents a brief overview of studies on the prevention of cancer and cardiometabolic diseases by tea. The major focus is on green tea catechins concerning the effective doses used, the mechanisms of action, and possible toxic effects. In cancer prevention by tea, the laboratory results are strong; however, the human data are inconclusive, and the effective doses used in some human trials approached toxic levels. In studies of the alleviation of metabolic syndrome, diabetes, and prevention of cardiovascular diseases, the results from human studies are stronger in individuals who consume 3-4 cups of tea (600-900 mg of catechins) or more per day. The tolerable upper intake level of tea catechins has been set at 300 mg of (-)-epigallocatechin-3-gallate in a bolus dose per day in some European countries. The effects of doses and dosage forms on catechin toxicity, the mechanisms involved, and factors that may affect toxicity are discussed.

(3)  Schimidt HL, Garcia A, Martins A, Mello-Carpes PB, Carpes FP. Green tea supplementation produces better neuroprotective effects than red and black tea in Alzheimer-like rat model. Food Res Int. 2017 Oct;100(Pt 1):442-448. doi: 10.1016/j.foodres.2017.07.026.

(4)   Yang K, Gao ZY, Li TQ, Song W, Xiao W, Zheng J, Chen H, Chen GH, Zou HY. Anti-tumor activity and the mechanism of a green tea (Camellia sinensis) polysaccharide on prostate cancer. Int J Biol Macromol. 2019 Feb 1;122:95-103. doi: 10.1016/j.ijbiomac.2018.10.101.

(5)  Khan G, Haque SE, Anwer T, Ahsan MN, Safhi MM, Alam MF. Cardioprotective effect of green tea extract on doxorubicin-induced cardiotoxicity in rats. Acta Pol Pharm. 2014 Sep-Oct;71(5):861-8.

Abstract. The in vivo antioxidant properties of green tea extract (GTE) were investigated against doxorubicin (DOX) induced cardiotoxicity in rats. In this experiment, 48 Wistar albino rats (200-250 g) were divided into eight groups (n = 6). Control group received normal saline for 30 days. Cardiotoxicity was induced by DOX (20 mg/kg ip.), once on 29th day of study and were treated with GTE (100, 200 and 400 mg/kg, p.o.) for 30 days. Aspartate aminotransferase (AST), creatinine kinase (CK), lactate dehydrogenase (LDH), lipid peroxidation (LPO), cytochrome P450 (CYP), blood glutathione, tissue glutathione, enzymatic and non-enzymatic antioxidants were evaluated along with histopathological studies. DOX treated rats showed a significant increased levels of AST, CK, LDH, LPO and CYP, which were restored by oral administration of GTE at doses 100, 200 and 400 mg/kg for 30 days. Moreover, GTE administration significantly increased the activities of glutathione peroxidase (GPX), glutathione reductase (GR), glutathione s-transferase (GST), superoxide dismutase (SOD) and catalase (CAT), in heart, which were reduced by DOX treatment. In this study, we have found that oral administration of GTE prevented DOX-induced cardiotoxicity by accelerating heart antioxidant defense mechanisms and down regulating the LPO levels to the normal levels.

(6) Takada M, Yamagishi K, Iso H, Tamakoshi A. Green tea consumption and risk of hematologic neoplasms: the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study).  Cancer Causes Control. 2019 Aug 26. doi: 10.1007/s10552-019-01220-z.

Abstract. Purpose: Experimental studies suggested that green tea may have an anticancer effect on hematologic neoplasms. However, few prospective studies have been conducted. Methods: A total of 65,042 individuals aged 40-79 years participated in this study and completed a self-administered questionnaire about their lifestyle and medical history at baseline (1988-1990). Of these, 52,462 individuals living in 24 communities with information on incident hematologic neoplasms available in the cancer registry, who did not have a history of cancer and provided valid information on frequency of green tea consumption, were followed through 2009. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of hematologic neoplasms according to green tea consumption were analyzed. Results: The incidence of hematologic neoplasms during a median follow-up of 13.3 years was 323. Compared with the never-drinkers of green tea, the multivariate HRs and 95% CIs for total hematologic neoplasms in green tea drinkers of ≤ 2 cups/day, 3-4 cups/day, and ≥ 5 cups/day were 0.65 (0.42-1.00), 0.73 (0.47-1.13), and 0.63 (0.42-0.96), respectively. The association was more prominent for acute myeloid leukemias and follicular lymphomas. Conclusions: The present cohort study suggests a protective effect of green tea against hematologic neoplasms, especially acute myeloid leukemias.

Kuriyama S. The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies. J Nutr. 2008 Aug;138(8):1548S-1553S. doi: 10.1093/jn/138.8.1548S.

Abstract. Although substantial evidence from in vitro and animal studies indicates that green tea preparations inhibit cardiovascular disease processes, the possible protective role of green tea consumption against this disease in humans remains unclear. We conducted a population-based prospective cohort study (the Ohsaki Study) to examine the association between green tea consumption and mortality from cardiovascular disease (CVD), cancer, and all causes with 40,530 persons in Miyagi prefecture, in northern Japan. Previously published work has shown that green tea consumption was inversely associated with mortality from CVD and all causes. The inverse association of mortality from CVD was more pronounced in women (P = 0.08 for interaction with sex). In women, the multivariate hazard ratios (95% confidence intervals) of CVD mortality across increasing green tea consumption categories were 1.00, 0.84 (0.63-1.12), 0.69 (0.52-0.93), 0.69 (0.53-0.90) (P for trend = 0.004). Within CVD mortality, the stronger inverse association was observed for stroke mortality. Because our observational study has found the inverse association, I report here the results of a review of epidemiological evidence from randomized controlled trials (RCT) of the association between green tea or green tea extracts and CVD risk profiles. More than half of the RCT have demonstrated the beneficial effects of green tea on CVD risk profiles. These results from RCT suggest a plausible mechanism for the beneficial effects of green tea and provide substantial support for our observations.