Extraction and Quantification of Sinapinic Acid from Irish Rapeseed Meal and Assessment of Angiotensin-I Converting Enzyme (ACE-I) Inhibitory Activity

Phenolic compounds, including phenolic acids, are known to play a protective role against the development of cardiovascular disease. The aim of this work was to generate a phenolic acid extract from Irish rapeseed meal, to determine the quantity of sinapinic acid (SA) in this fraction and to assess the ability of this fraction to inhibit the enzyme angiotensin-I converting enzyme (ACE-I; EC 3.4.15.1). A crude phenolic extract (fraction 1), free phenolic acid containing extract (fraction 2), and an extract containing phenolic acids liberated from esters (fraction 3) were generated from Irish rapeseed meal using a methanol:acetone:water solvent mixture (7:7:6). The total phenolic content (TPC) of each extract was determined and proximate analysis performed to determine the fat, moisture, and protein content of these extracts. Nuclear magnetic resonance (H-1 NMR) spectroscopy was used to quantify the level of SA in extract 3, which inhibited ACE-I by 91% +/- 0.08 when assayed at a concentration of 1 mg/mL, compared to the control, captopril, which inhibited ACE by 97% +/- 0.01 when assayed at a concentration of 1 mg/mL.