Hypotensive effect of sweetpotato tops

Abstract

Sweetpotato tops exhibited angiotensin I-converting enzyme (ACE) inhibitory activity, with different levels of activity in the constituent parts of the tops. Leaves showed the highest activity, while that of stems and petioles was much reduced. Since there appeared to be a relationship between ACE inhibitory activity and the total content of the caffeoylquinic acids in the constituent parts, the ACE inhibitory activity of each caffeoylquinic acid was analyzed. 3,4,5-tri-O-caffeoylquinic acid (3,4,5-triCQA) showed the strongest activity, followed by 3,4-di-O-caffeoylquinic acid (3,4-diCQA), and 4,5-di-O- caffeoylquinic acid (4,5-diCQA). Spontaneously hypertensive rats (SHR) which were orally administered sweetpotato tops exhibited dose-dependent suppression in blood pressure increases in comparison with the control group. These results suggest that sweetpotato tops have a hypotensive effect in SHR, which is at least in part due to the ACE inhibitory activity of caffeoylquinic acids.