Onion Vinegar Quality Evaluation and its Alleviate Oxidative Stress Mechanism in Caenorhabditis elegans Via SKN-1

Abstract

Recently, there has been renewed interest in biorefining of agricultural onion into functional products. In this study, onion vinegar (OV) are prepared by a two-stage semi-continuous fermentation method, and its content of total flavonoids (3.01 mg/mL) and polyphenols (976.76 μg/mL) is superior to other commercial vinegars. OV possesses a high radical scavenging activity and enhances the antioxidant enzyme activities in vivo, alleviating intracellular oxidative stress in Caenorhabditis elegans. Treated by OV, the 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH·), diammonium 2,2′-azino-bis (3-ethylbenzo thiazoline-6-sulfonic acid) (ABTS+·) and 2-phenyl-4,4,5,5- tetramethylimidazoline-1-oxyl 3-Oxide (PTIO·) free radicals clearance rates are 88.76, 98.76 and 90.54%, respectively in vitro. Whereas the glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) enzyme activities in C. elegans reach 271.57, 129.26, and 314.68%, respectively. Using RNAi and RT-PCR, it has been further confirmed that OV modulates transcription factor SKN-1, the nuclear factor erythroid 2-related factor 2 (Nrf2) homologous, in C. elegans, enhancing the resistance of C. elegans against sodium arsenite stress. Lifespan analysis reveals that 1 mL OV extends the maximum lifespan of the nematode to 26 days. Evidence is presented which shows that OV increases the lifespan of C. elegans by activating the SKN-1 signaling pathway. Overall, the OV is a well functional condiment, enhancing the value-added of onion.

Preparation of Dendrobium officinale Flower Anthocyanin and Extended Lifespan in Caenorhabditis elegans

“…The antioxidative active factors upon exogenous stimulation of C. elegans was reported to reduce oxidative damage in vivo [ 5 ]. This motivated us to speculate whether D. officinale ACNs can also alleviate oxidative stress in C. elegans .…”

“…Notably, the SOD activity reached 1.3087 ± 0.4451 U/mg prot ( p < 0.05). SOD and CAT, two major antioxidant enzymes in C. elegans , have the main function of scavenging superoxide free radicals and H 2 O 2 [ 5 ]. The results indicated that the ACNs from D. officinale mainly increased the SOD activity, while the effect on CAT and GSH-Px activity was not obvious.…”

“…In a previous study, ACNs were shown to reduce the amount of ROS, and to render the worms more tolerant against heat and oxidative stress [ 12 , 45 ]. We observed that ACNs from D. officinale could relieve stress, increasing the average survival time under heat stress by approximately 50%, and efficiently resisting the oxidative stress induced by H 2 O 2 within 6 h. It has been reported that prolonging lifespan and mediating aging is facilitated by SKN-1 [ 5 , 8 ] or by the insulin/IGF-like pathway that regulates the DAF-16 factor [ 9 , 30 ]. However, in this study, the mechanism of antioxidation and anti-aging effects has not been thoroughly studied, which will motivate us to carry out further research.…”

“…The DPPH· free radical clearance activity was determined according to our previous work [ 5 ]. The 0.3 mL sample and 2.7 mL DPPH solution (dissolved in methanol, 0.5 mM) were mixed, letting it stand and avoiding light reaction for 20 min.…”

“…Currently, Caenorhabditis elegans is a well-established model in genetics, which has been fully sequenced and is widely utilized in aging-related studies due to its short life cycle, rapid reproduction rate, and clear life extension mechanism [ 2 , 5 , 6 ]. It has been reported that some natural products have been shown to increase the lifespan of C. elegans , such as flavonoids [ 7 , 8 , 9 , 10 ], saponins [ 11 , 12 ], polysaccharides [ 13 , 14 ], cereal, and food-derived oil [ 15 ].…”