Proteins isolated from the humble potato may be biologically active and capable of reducing blood pressure, as well as having antioxidant activity, Finnish researchers report.
Isolated proteins, obtained as processing waste from the potato industry, could form hydrolysates which possessed angiotensin converting enzyme (ACE)-inhibitory activity, report the researchers in the journal Food Chemistry.
"The results of this study suggest that potato is a promising source for the production of bioactive compounds as ingredients for developing functional foods with a beneficial impact on cardiovascular health," wrote lead author Anne Pihlanto from MTT Agrifood Research Finland.
The Finnish researchers isolated the proteins from potato tubers (Solanum tuberosum) and subjected to a treatment with alcalase, neutrase and esperase enzymes.
Hydrolysis of the potato protein isolates (breaking down of the compound by reacting with water) produced proteins with an increased activity for ACE-inhibition and radical scavenging activity, reports Pihlanto.
ACE inhibitors work by inhibiting the conversion of angiotensin I to the potent vasoconstrictor, angiotensin II, thereby improving blood flow and blood pressure.
High blood pressure (hypertension),defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, is a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
ACE inhibitors made by drug companies have been found to be beneficial in treating hypertension, particularly in patients with type-1 or type-2 diabetes, and also appear to provide good cardiovascular and renal protection. Pharmaceutical ACE-inhibitors do however have side effects.
The researchers report that the ACE-inhibitory potencies of the hydrolysates were high, while the proteins also showed some, but lesser, activity before hydrolysis.
In addition, the samples also showed a limited antioxidant activity, as measured using the total radical-trapping potential (TRAP) method. Subjecting the protein isolates to a tow-hour hydrolysis did increase the antioxidant activity, added the researchers.
"The most active sample was the potato liquid alcalase hydrolysate, which produced an antioxidant capacity of 0.48 grams dry matter, equivalent to one millimole of trolox by the TRAP method," they stated.
Commenting on the ACE-inhibitory activity, Pihlanto and co-workers indicated that this was most likely related to the peptides and /or free amino acids produced during the enzymatic treatment. They could not, however, rule out the possibility of other unknown compounds.
The researchers reported that future should focus on identifying the active compounds, as well as verifying the antihypertensive activity of the potato protein hydrolysates in vivo.
"Food by-products have the additional advantage of representing a value-added outlet for inexpensive starting material," wrote the researchers.
"An economic analysis for the whole process from the collection of by-products to the production of the powered peptide mixture would provide valuable information for the food industry," they concluded.
The study was financed by the National Technology Agency of Finland (TEKES) through the Innovation in Food Programme.
2008: It's all about spuds
The FAO has declared that 2008 is the International Year of the Potato (IYP), in an attempt to raise awareness for the importance of the tuber.
With the growing global population, the FAO sees the potato as an important part of the effort to ensure food security for the current and future generations.
According to the IYP website, "The potato should be a major component in strategies aimed at providing nutritious food for the poor and hungry. It is ideally suited to places where land is limited and labour is abundant, conditions that characterize much of the developing world. The potato produces more nutritious food more quickly, on less land, and in harsher climates than any other major crop - up to 85 per cent of the plant is edible human food, compared to around 50 per cent in cereals."
Source: Food Chemistry (Elsevier)
Volume 109, Issue 1, Pages 104-112
"ACE-inhibitory and antioxidant properties of potato (Solanum tuberosum)"
Authors: Anne Pihlanto, S. Akkanen, H.J. Korhonen