Abstract
Purpose: To investigate the blood pressure-lowering effect of green tea (GT) extract alone and in combination with an angiotensin converting enzyme (ACE) inhibitor, perindopril, on rats.
 Methods: The study consisted of four groups of five spontaneously hypertensive rats (SHR): negative control (2 % tragacanth mucilage), positive control group (perindopril, 0.36 mg/kg/day) and two treatment groups (green tea, 25 mg/kg/day; and combined green tea/perindopril). The treatments were given orally for 14 days. Systolic blood pressure was measured before and after treatment using the tail cuff technique. Angiotensin converting enzyme activity in the lung homogenate of the hypertensive rats was determined spectrophotometrically.
 Results: Green tea extract significantly reduced the rats’ systolic blood pressure (p < 0.05) but did not inhibit the angiotensin-converting enzyme. The combination of green tea extract with perindopril also caused a significant decline in blood pressure (p < 0.001). However, the green tea extract attenuated the inhibition of the angiotensin-converting enzyme activity by perindopril.
 Conclusion: Green tea extract produces anti-hypertensive activity in rats, but its mechanism of action is not via inhibition of angiotensin-converting enzyme. The interaction of GT extract with perindopril results in a reduction of ACE inhibitory activity.
Highlights
Hypertension is one of the significant public health problems worldwide
Green tea (GT): green tea extract (p < 0.05) by 12.634 ± 4.06 mmHg when compared to vehicle control, whilst perindopril (0.36 mg/kg) lowered systolic blood pressure (SBP) by 23.11 ± 4.08 mmHg (p < 0.001)
No significant reduction of blood pressure was found between green tea extract versus perindopril at the concentration used in this study
Summary
Hypertension is one of the significant public health problems worldwide This disease is prevalent in both developing and developed countries, and is estimated to be the cause for 4.5 % of the global disease burden [1]. GT is the least fermented form of tea [4] Flavonoids, catechins such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC) from GT are responsible for the various therapeutic effects of GT including antihypertensive [5], antiinflammatory [6], and antioxidant [7]. Little is known on whether green tea can inhibit ACE activity in hypertensive rats
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