The inhibitory action of purple tea on in vivo starch digestion compared to other Camellia sinensis teas

Tamires Barlati Vieira Da Silva,Pâmela Alves Castilho,Anacharis Babeto De Sá-Nakanishi,Flávio Augusto Vicente Seixas,Maria Inês Dias,Lillian Barros,Isabel C.F.R Ferreira,Adelar Bracht,Rosane Marina Peralta

doi:10.1016/j.foodres.2021.110781

Tamires Barlati Vieira Da Silva, Pâmela Alves Castilho + Show 7 more

Open Access

https://doi.org/10.1016/j.foodres.2021.110781

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Abstract

In order to contribute to improve knowledge about the actions of Camellia sinensis extracts on starch digestion, several varieties were compared. The latter were green, oolong, white, black, and purple teas. The results are hoped to contribute to our understanding of the mode of action and potency of the various tea preparations as possible adjuvants in the control of post-prandial glycemia. The extracts were prepared in way similar to their form of consumption. All extracts decreased starch digestion, but the purple tea extract was the strongest inhibitor, their inhibitory tendency started at the dose of 50 mg/kg and was already maximal with 250 mg/kg. Maltose tolerance was not significantly affected by the extracts. Glucose tolerance was not affected by purple tea, but black tea clearly diminished it; green tea presented the same tendency. Purple tea was also the strongest inhibitor of pancreatic α-amylase, followed by black tea. The green tea, oolong tea, and white tea extracts tended to stimulate the pancreatic α-amylase at low concentrations, a phenomenon that could be counterbalancing its inhibitory effect on starch digestion. Based on chemical analyses and molecular docking simulations it was concluded that for both purple and black tea extracts the most abundant active component, epigallocatechin gallate, seems also to be the main responsible for the inhibition of the pancreatic α-amylase and starch digestion. In the case of purple tea, the inhibitory activity is likely to be complemented by its content in deoxyhexoside-hexoside-containing polyphenolics, especially the kaempferol and myricetin derivatives. Polysaccharides are also contributing to some extent. Cyanidins, the compounds giving to purple tea its characteristic color, seem not to be the main responsible for its effects on starch digestion. It can be concluded that in terms of postprandial anti-hyperglycemic action purple tea presents the best perspectives among all the tea varieties tested in the present study.

Highlights

Type 2 diabetes mellitus is the most common type of diabetes and its complications are a major global health problem (Wasana, Attanayake, Weerarathna, & Jayatilaka, 2021)
Phenolic compounds are generally believed to constitute the main bioactive compounds and inhibitors of α-amylases in Camellia sinensis extracts and, for this reason, all extracts used in this study were char acterized in terms of their contents in these compounds, using the analytical procedures described in the Section 2
The contents are all expressed as quantities per gram extract and they represent the amounts that were effectively extracted using the procedure described in the methods section

Summary

Introduction

Type 2 diabetes mellitus is the most common type of diabetes and its complications are a major global health problem (Wasana, Attanayake, Weerarathna, & Jayatilaka, 2021). Inhibition of starch digestion by ingesting α-amylase and α-glucosidase inhibitors is an especially effective way of diminishing post-prandial glycemia, but the drugs commonly used, such as acarbose, present several negative effects (Awosika & Aluko, 2019; Gutierrez-Grijalva, Antunes-Ricardo, Acosta-Estrada, Gutierrez-Uribe, & Basilio Heredia, 2019). For this reason, there has been continuous efforts at discovering natural antidiabetic agents that could provide mild anti-hyperglycemic protection by virtue of a continuous ingestion in conjunction with the regular and daily food intake. Nyambe-Silavwe et al (2015) claim that their green tea preparation inhibited the human salivary α-amylase with a IC50 of 8.9 μg/mL when amylose was the substrate and of 25 to 69 μg/mL when amylopectin was the substrate, numbers that are not in agreement with those reported by Gao et al (2013) and Miao et al(2015). Yang and Kong (2016), on the other hand, reported biphasic effects for green, oolong and black tea extracts in addition to a polyphenolic preparation extracted from Camellia sinensis: stimulation at low concentrations, followed by inhibition at higher ones

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