Generation of phenolic-rich extracts from brewers' spent grain and characterisation of their in vitro and in vivo activities

Brewers' spent grain (BSG) is a co-product of the brewing industry, which is rich in phenolic acids. This study compared the in vitro bioactive properties of aqueous, aqueous pH-shift and enzyme-aided phenolic extracts from pale (unroasted) wet BSG. Overall, the pH-shift extracts showed higher oxygen radical absorbance capacity (ORAC), trolox equivalent antioxidant capacity (TEAC) and ferric-reducing antioxidant power (FRAP) values compared with the enzyme-aided extracts. A selected enzyme-aided extract showed highest in vitro ACE inhibitory activity (ACE IC₅₀: 0.133 ± 0.032 mg mL⁻¹) and mediated significant (p < 0.05) reductions in blood pressure markers in vivo following ingestion by spontaneously hypertensive rats (systolic blood pressure; −35.35 ± 9.04 and diastolic blood pressure; −28.55 ± 4.22 mmHg). The results demonstrated that the observed in vitro activity of phenolic-rich extracts may be translated into an in vivo hypotensive effect. Enzyme-assisted extraction has potential as an alternative solvent-free approach for generating phenolic-rich extracts from BSG that may find use in the management of hypertension.