Abstract
The objectives of the study were to test the biological activities of peppermint and spearmint oils via (i) measuring in vitro anti-inflammatory effects with porcine alveolar macrophages (PAMs), (ii) determining the barrier integrity of IPEC-J2 by analyzing transepithelial electrical resistance (TEER), (iii) testing their antioxidant activities, and (iv) investigating the antimicrobial activity against enterotoxigenic Escherichia coli (ETEC) F18+. Briefly, (i) macrophages were seeded at 106 cells/mL and treated (24 h) with mint oils and lipopolysaccharide (LPS). The treatments were 2 (0 or 1 μg/mL of LPS) × 5 (0, 25, 50, 100, 200 µg/mL of mint oils). The supernatants were collected for TNF-α and IL-1β measurement by ELISA; (ii) IPEC-J2 cells were seeded at 5 × 105 cells/mL and treated with mint oils (0, 25, 50, 100, and 200 μg/mL). TEER (Ωcm2) was measured at 0, 24, 48, and 72 h; (iii) the antioxidant activity was assessed (0, 1, 50, 100, 200, 500, and 600 mg/mL) using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and reducing power assays; (iv) overnight-grown ETEC F18+ were quantified (CFU/mL) after supplementing with peppermint and spearmint oils (0, 1.44, 2.87, 5.75, 11.50, and 23.00 mg/mL). All data were analyzed using the MIXED procedure. Both mint oils significantly inhibited (p < 0.05) IL-1β and TNF-α secretion from LPS-stimulated PAMs. Mint oil treatments did not affect TEER in IPEC-J2. Spearmint and peppermint oils exhibited (p < 0.05) strong antioxidant activities in DPPH and reducing power assays. Both mint oils also dose-dependently inhibited (p < 0.05) the growth of ETEC F18+ in vitro. The results of the study indicated that both mint oils are great candidate feed additives due to their in vitro anti-inflammatory, antioxidant, and antimicrobial effects. Further research is needed to evaluate their efficacy in vivo.
Highlights
Introduction iationsPost-weaning is a critical phase in swine production, where piglets are exposed to a combination of stressors [1] that are associated with fluctuations in gut function and cause different multifactorial diseases [2]
No cytotoxic effects were observed at the highest dose of both mint oils, because all wells showed ≥ 76% cell viability compared with control cells without LPS challenge
The results of the present study reported that both peppermint and spearmint oils inhibited the production of pro-inflammatory cytokines from LPS-stimulated porcine alveolar macrophages, demonstrating the high therapeutic potential of these herbs
Summary
Introduction iationsPost-weaning is a critical phase in swine production, where piglets are exposed to a combination of stressors [1] that are associated with fluctuations in gut function and cause different multifactorial diseases [2]. Due to the increase in antibiotic resistance [3], antibiotics as growth-promoting agents have been banned in the EU since 2006 [4]. The first adopted alternative to in-feed antibiotics was the widespread application of high doses of zinc oxide, which, despite their antibacterial and anti-inflammatory activities, raised concerns related to environmental pollution [5,6]. The use of high-dose zinc in feed may have contributed to the emergence of methicillin-resistant Staphylococcus aureus (MRSA). As this metal is associated with the co-selection of resistance genes to antibiotics [7,8]. The EU recently banned the inclusion of pharmacological levels of zinc oxide in animal feed after 2022 [9]. The role of nutrition and novel functional feed additives and ingredients
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