The secondary metabolites profiling of Nymphaea nouchali stem (NNSE) extract was carried out using a high-resolution mass spectroscopic technique. The antioxidant effects of NNSE, as well as the underlying mechanisms, were also investigated in tert-butyl hydroperoxide (t-BHP)-stimulated oxidative stress in RAW264.7 cells. Tandem mass spectroscopy with (−) negative mode tentatively revealed the presence of 54 secondary metabolites in NNSE. Among them, phenolic acids and flavonoids were predominant. Phenolic acids (brevifolincarboxylic acid, p-coumaroyltartaric acid, niazinin B, lalioside, 3-feruloylquinic acid, and gallic acid-O-rutinoside), flavonoids (elephantorrhizol, apigenin-6-C-galactoside 8-C-arabinoside, and vicenin-2), sialic acid (2-deoxy-2,3-dehydro-N-acetylneuraminic acid), and terpenoid (α-γ-onoceradienedione) were identified in NNSE for the first time. Unbridled reactive oxygen species/nitrogen species (ROS/RNS) and redox imbalances participate in the induction and development of many oxidative stress-linked diseases. The NNSE exhibited significant free radical scavenging capabilities and was also able to reduce t-BHP-induced cellular generation in RAW264.7 cells. The NNSE prevented oxidative stress by inducing the endogenous antioxidant system and the levels of heme oxygenase-1 (HO-1) by upregulating Nrf2 through the modulation of mitogen-activated protein kinases (MAPK), such as phosphorylated p38 and c-Jun N terminal kinase. Collectively, these results indicate that the NNSE exhibits potent effects in preventing oxidative stress-stimulated diseases and disorders through the modulation of the MAPK/Nrf2/HO-1 signaling pathway. Our findings provide new insights into the cytoprotective effects and mechanisms of Nymphaea nouchali stem extract against oxidative stress, which may be a useful remedy for oxidative stress-induced disorders.

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This study characterized a lactic acid bacterium Leuconostoc mesenteroides HJ69 at biochemical and molecular level, isolate from traditional Korean fermented food Kimchi. Cell free supernatant (CFS) of L. mesenteroides HJ69 exhibited significant (P < 0.05) antibacterial effect as diameters of inhibition zones (14.34 ± 0.31 – 18.21 ± 0.23 mm) against the tested foodborne pathogenic bacteria with minimum inhibitory concentration and minimum bactericidal concentration values found in the range of 250–2,000 and 500–2,000 μg/mL, respectively. Further, CFS of L. mesenteroides HJ69 revealed its mode of action on membrane integrity as confirmed by the increased release of potassium ions (800 and 750 mM/L), loss of 260‐nm absorbing materials (3.85 and 3.77 OD), and increase in relative electrical conductivity (8.6 and 8.2%) against two selected bacteria L. monocytogenes KCTC‐3569 (Gram‐positive) and Escherichia coli O157:H7 (Gram‐negative), respectively. The above findings hypothesize that L. mesenteroides HJ69 compromised its mode of action on membrane integrity, suggesting its enormous potential in the food industry. Practical Applications Asian countries have enormous use of fermented food products enriched with large populations of health‐beneficial lactic acid bacteria (LAB). This study describes the isolation of a LAB strain Leuconostoc mesenteroides HJ69 from traditional Korean fermented food Kimchi along with its biochemical and molecular characterization. The cell free supernatant of L. mesenteroides HJ69 displayed remarkable antibacterial effect against various foodborne pathogenic bacteria with a hypothesized mode of action in several assays. These findings suggest that L. mesenteroides HJ69 could be an effective candidate for its practical application in food industry to control the proliferation of foodborne pathogenic bacteria as a natural antimicrobial agent.

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