Bioactive components of tempe and soy protein concentrate with blood pressure lowering potential

Hypertension is a major global health problem that increases the risk of cardiovascular disease, kidney failure, and stroke. Previous studies have shown that consumption of soy and its processed products can help lower blood pressure. Tempe fermentation is known to improve the nutritional and functional properties of soy-based products. However, research regarding the specific bioactive components responsible for its antihypertensive properties is limited. This study aimed to compare the metabolite profile, amino acid composition, antioxidant capacity, and angiotensin-converting enzyme (ACE) inhibitory activity of tempe protein concentrate (TPC) and soy protein concentrate (SPC). Metabolite profiling was performed using gas chromatography–mass spectrometry and ultra-high-performance liquid chromatography–mass spectrometry. Amino acid composition, DPPH radical scavenging, and ACE inhibitory activity were determined using standard analytical methods. TPC exhibited higher antioxidant capacity than SPC (38 and 33 mg AEAC/100 g), expressed as ascorbic acid equivalent antioxidant capacity. Multivariate analyses (PCA and OPLS) revealed distinct metabolite profiles between TPC and SPC, with fermentation contributing to the enrichment of bioactive compounds such as isoflavones, γ-aminobutyric acid (GABA), meglutol, and several amino acids that were positively correlated with ACE inhibition. TPC also demonstrated stronger ACE inhibitory activity, as indicated by a lower IC₅₀ value compared with SPC (104.25 vs. 238.91 ppm). UHPLC-MS analysis further showed that TPC contained a greater diversity of bioactive peptides, including ACE inhibitory, hypotensive, and vasodilator peptides. These findings indicate that fermentation significantly modifies soy composition and improves its bioactivity, supporting the potential of tempe-derived protein as functional food ingredients for hypertension management.