Abstract
This study evaluates the potential mechanism of action and bioactivity of black tea and black tea pomace for type 2 diabetes prevention via inhibition of carbohydrate hydrolyzing enzymes. Black tea leaves were extracted in hot water and black tea pomace was extracted in 70% acetone. The phenolic content of the water extract (WBT) and pomace acetone extracts (AOBT) were 5.77 and 8.9 mg/mL, respectively, both based on the same concentration of solid tea in the extract. The water extract was subjected to C18 extraction and the resulting hydrophobic fraction (HBBT) was further subjected to LH-20 extraction to recover a low molecular weight phenolic enriched fraction (LMW) and a high molecular weight enriched fraction (HMW). The phenolic content of the LMW and HMW fraction were 1.42 and 2.66 mg/mL, respectively. Among water extracts the HMW fraction was most bioactive against α-glucosidase (IC50 = 8.97 μg/mL) followed by HBBT fraction (IC50 = 14.83 μg/mL). However, the HBBT fraction was the most bioactive fraction against α-amylase (IC50 = 0.049 mg/mL). The black tea pomace (AOBT) had significant α-glucosidase inhibitory activity (IC50 = 14.72 μg/mL) but lower α-amylase inhibitory activity (IC50 = 0.21 mg/mL). The phenolic profiles for LMW and HMW fractions were evaluated using HPLC and the differences between the two profiles were identified. Further research is underway to identify and evaluate the phenolic compounds that are present in the HMW fraction. Our findings suggest that black tea and black tea pomace has potential for carbohydrate hydrolyzing enzyme inhibition and this activity depends on high molecular weight phenolic compounds.
Highlights
According to International Diabetes Federation (IDF) worldwide 382 million people in 2013 had diabetes and this number is projected to increase to 592 million by 2035 [1]
Recent research has shown that phenolic compounds have the potential to inhibit carbohydrate hydrolyzing enzymes in our digestive organs and have potential to play a role in management of type 2 diabetes [6]
Our findings suggest that the black tea pomace contains hydrophobic compounds that are not extracted during hot water extraction, which have significant potential for type 2 diabetes prevention via inhibition of carbohydrate hydrolyzing enzymes
Summary
According to International Diabetes Federation (IDF) worldwide 382 million people in 2013 had diabetes and this number is projected to increase to 592 million by 2035 [1]. This dramatic increase is mainly due to the increasing incidence of type 2 diabetes [1], called non-insulin-dependent diabetes, which is caused by the body’s ineffective use of insulin [2]. The American Diabetes Association defines pre-diabetic individual as an individual with blood glucose levels higher than normal (impaired fasting glucose between 100 and 125 mg/dL, impaired glucose tolerance between 140 and 199 mg/dL, and HbA1c between 5.7 and 6.4%) but not high enough to be considered. Recent research has shown that phenolic compounds have the potential to inhibit carbohydrate hydrolyzing enzymes in our digestive organs and have potential to play a role in management of type 2 diabetes [6]
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