Preliminary analysis of eight brands of green tea commercially available in Kuwait

Abstract

Green tea is known for its beneficial effects and content of polyphenols. However, no data is available on the composition of the brands of green tea available in the Kuwaiti market. Limited analysis of components in 8 locally available brands of green tea was carried out. The analysis included total phenol content, bioactive polyphenols (catechins), caffeine and antioxidants, as well as analysis of ascorbic acid, fatty acids and trace metals. Total phenols ranged between 6.46–40.40 mg/g dry weight (DW). (−)‐epigallocatechin gallate (EGCG) and (−)‐epicatechin (EC) contents ranged from 162–654 and 78–386 mg/g DW, respectively. Magnesium was the major metal in all brands of green tea with heavy metals, such as cadmium having variable levels (0.7–15.4 mg/kg DW). Five fatty acids (palmitic, oleic, linoleic, 11‐eicosaenoic, cis‐15‐tetracosenoic) were found in most of the brands of green tea analyzed. Ascorbic acid levels ranged from 0.650 to 0.904 mg/g DW and total antioxidants were between 2.10 and 3.25 mmole/g DW. We report that the 2 brands of green tea having the highest levels of phenols, polyphenols and antioxidants are Al‐Wazzah and Lipton. The major catechin, EGCG, was purified by preparative HPLC and assessed for anti‐diabetic activity in streptozotocin (STZ)‐induced diabetic rats during a 4 week daily treatment experiment. EGCG (100 mg orally daily) was effective in limiting weight loss and lowering blood glucose levels of diabetic rats. In addition, EGCG was effective in decreasing polydipsia and hypertension typical of diabetic rats.Support or Funding InformationThe study was supported by KU grant #SL 01/15.