Ingestion of Apios americana Medikus tuber suppresses blood pressure and improves plasma lipids in spontaneously hypertensive rats

The edible tuber of Apios americana Medikus, native to North America, has high nutritional values that attract consumers' attention and has been cultivated widely in northern Japan. This study was designed to verify the antihypertensive and hypolipidemic effects of A americana as physiological actions. In male spontaneously hypertensive rats (SHR) fed a diet containing 5% Apios powder for 3 weeks, blood pressure was lowered by 10%, and plasma triacylglycerol, and hepatic total cholesterol were decreased. In a diet with additional 1% cholesterol, ingestion of A americana decreased blood pressure and showed a tendency to decrease plasma total cholesterol in SHR. At 0.5 and 1 hours after a single oral administration of water extract of Apios at 200 mg/kg, which was rich in proline, blood pressure was lowered by 10% in male SHR. Therefore, it was expected that proline-rich peptide, which was derived from protein of A americana during digestion, contributed to the antihypertensive action. It is suggested that A americana is a healthy food material for prevention of hypertension and hyperlipidemia.