ACE-inhibitory, biological, and nutritional properties of Iranian red-garlic (Allium sativum L) peptides: Conformational changes under different processing
Zahra Akbarbaglu, Mandana Tayefe, Azin Nasrollah Zadeh, Roshanak Zolqadri, Narges Mazloomi, Atena Ramezani, Khashayar Sarabandi
Abstract
The aim of this study was to produce peptides obtained from enzymatic hydrolysis of Iranian red-garlic ( Allium sativum L ) protein (RGP) using different proteases (pepsin, Alcalase, trypsin, pancreatin). In the current work, the nutritional quality, antioxidant, antibacterial, and structural properties as well as ACE-inhibitory of RGP and hydrolysates (RGPH) were analyzed. Also, conformational changes and biological stability of RGP and RGPHs were evaluated during heat and acid treatments. RGPH demonstrated stronger Cu 2+ (28.27%) and Fe 2+ (44.03%) chelating activity, ABTS (89.57%), TEAC value (2.28), hydroxyl radicals (63.4%), nitric-oxide (63.23%), reducing power (1.26), DPPH (78.57%), total antioxidant (1.68) and functional properties (water and oil holding capacity) rather than that of RGP (Cu 2+ : 7.9%, Fe 2+ : 22.1%, ABTS: 47.1%, TEAC: 1.2, OH: 31.8%, NO: 13.1%, RP: 0.43, DPPH: 42.0%, and TAA: 0.64). The alcalase-RGPHs indicated the highest ACE inhibitory (71.97%). The enzymatic process, heating, and acidic treatment resulted in significant changes in unfolding, secondary structures of amide es I, II, A, and B regions, and increased aggregation of RGP. Among RGP and RGPHs, pepsin-RGPHs showed the best antibacterial against E. coli (40.67mm) and B. cereus (45.67mm). In addition, the amino acid profile demonstrated the high quality of RGP and RGPH as reliable sources of digestible essential (25%), antioxidant (20%), and hydrophobic (37%) amino acids. Considering the results, alcalase-RGPHs had the best techno-functional and biological activities (except for antibacterial) which can be considered as a natural antioxidant, stabilizer and preservative for food (especially various sauces and meat formulations) or medicinal purposes. • Hydrolysis of red-garlic protein (RGP) was done with different proteases. • RGP hydrolysates (RGPHs) had high biological activities, ACE inhibition and nutritional value. • RGPHs indicated superior functional properties, and antioxidant and metal-chelating activity. • Various conditions (pH, temperature) changed the unfolding and secondary structures of RGP. • Pepsin hydrolysates showed the highest antibacterial activity against E. coli and B. cereus.