Antioxidant and antibacterial properties of lemon, sweet, and cereal grasses

Abstract

Total phenolic content (TPC), antioxidant and antibacterial activity of ethanol, water, and water:ethanol (50/50 vol/vol) extracts from wheat, spelt, rye, barley, sweet, and lemon grasses were studied. Both grass type and solvent used significantly (p < .05; MANOVA) affected the extracts’ properties. The water:ethanol extract from lemon grass showed the highest TPC (107.24 ± 2.22 mg GAE/g d.m.), DPPH radical scavenging activity (87.8% inhibition), and FRAP value (1,445.2 ± 14.1 µmol Trolox/g d.m.). Rye and barley grass extracts also exhibited strong antioxidant potential. Spelt and lemon grass demonstrated the highest antimicrobial activity among the ethanol and water:ethanol extracts, whereas among the water extracts, only rye grass showed antibacterial activity against all of the tested indicator microorganisms. Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) were inhibited by extracts at a concentration of 0.3 mg/ml, whereas gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) needed higher extract concentrations (5–20 mg/ml). Grass extracts are thus a potential source of biologically functional compounds. Practical applications There is an ongoing, extensive search for natural ingredients that either prevent or retard undesirable changes, such as oxidation or microbiological contamination, which take place in food products. In this study, extracts from different types of grasses exhibited strong and moderate antioxidant and antibacterial activities, which thus makes it possible to use them as additives (antioxidants or preservatives) in the design of novel beverages and food products. The results obtained in this study could be an important asset to the food industry, as they provide new insight into plant extracts that have the potential to be used in food supplements, health drinks, or food products with enhanced health properties.