Inhibitory activity of angiotensin I-converting enzyme (ACE) was examined with (-)-epigallocatechin gallate (EGCG) metabolites produced by intestinal bacteria, together with tea catechins. All of the metabolites showed ACE inhibitory activities and the order of IC50 was hydroxyphenyl valeric acids > 5-(3,4,5-trihydroxyphenyl)-γ-valerolactone (1) > trihydroxyphenyl 4-hydroxyvaleric acid ≫ dihydroxyphenyl 4-hydroxyvaleric acid ≫ 5-(3,5-dihydroxyphenyl)-γ-valerolactone (2). Among the catechins, galloylated catechins exhibited stronger ACE inhibitory activity than nongalloylated catechins. Furthermore, the effects of a single oral intake of metabolites 1 and 2 on systolic blood pressure (SBP) were examined with spontaneously hypertensive rats (SHR). Significant decreases in SBP were observed between 2 h after oral administration of 1 (150 mg/kg in SHR) and the control group (p = 0.002) and between 4 h after administration of 2 (200 mg/kg in SHR) and the control group (p = 0.044). These results suggest that the two metabolites have hypotensive effects in vivo.
Keywords: angiotensin I-converting enzyme; blood pressure; epigallocatechin gallate; intestinal bacteria; metabolite; spontaneously hypertensive rat; valerolactone.