A Modified and Improved Assay Based on Microbial Test System (MTS) to Evaluate Antioxidant Activity

Abstract

An assay based on microbial test system (Escherichia coli) was developed to evaluate the antioxidant capacity of phytochemicals, extracts of plants, fruits, and vegetables. E. coli was cultured in Luria-Bertani (LB) medium. Quercetin was used as a standard in microbial test system (MTS) assay because it had high antioxidant activity and was easily and economically obtained. The cultivation times of E. coli entrance into mid-log phase, before and after H 2 O 2 addition for MTS assay were investigated, respectively. The concentrations of H 2 O 2 and tested compounds for MTS assay were also studied. The value (μ 30 ), t=30 min, the specific growth rate of E. coli in medium containing samples and 6.0 mM H 2 O 2 /the specific growth rate in medium containing only H 2 O 2 was calculated to evaluate the antioxidant activity. Pure compounds (quercetin, quercitrin, hyperoside, rutin, and kaempferol-3-O-α-L-rhamnoside), fruits (apple, banana, kiwi fruit), and vegetable (tomato) were used to verify this assay, and the results were compared to three in vitro antioxidant assays (2,2´-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) assay). The results indicated the MTS assay based on E. coli without transferring the antioxidant genes under peroxide stress would be useful to define the action of extracts or pure compounds as antioxidants. The proposed method is useful to evaluate antioxidant activity and more biologically relevant because it accounts for some aspects of uptake and location of antioxidants within bacterial cells.

Metabolite Profiles, Bioactivity, and HPLC Fingerprint of Different Varieties of Eucommia ulmoides Oliv.: Towards the Utilization of Medicinal and Commercial Chinese Endemic Tree

“…Escherichia coli were used to determine the antioxidant activity of extracts based on the method described by Smirnova and Zhou [ 35 , 36 ]. The bacteria were incubated in Luria—Bertani (LB) medium at 37 °C with shaking at 120 r/min overnight until they reached the midlog phase.…”

Evaluation of the chemical composition, antioxidant and anti-inflammatory activities of distillate and residue fractions of sweet basil essential oil

“…The model of DPPH and ABTS radical scavenging is a widely used method to evaluate the free radical scavenging ability of natural substances. The antioxidant activity of a compound can be presented as its ability to scavenge the radicals by measuring the decline in the absorbance (Zhou et al 2016). As seen in Table 3, the results indicated that the scavenging activity was in the order Rf [ Me [ Df [ Co [ Es. The ABTS radicals were generated by potassium persulfate and have a blue-green chromophore with a maximum absorption at 734 nm, which decreases in intensity in the presence of antioxidants.…”

Synergistic effects and related bioactive mechanism of Potentilla fruticosa L. leaves combined with Ginkgo biloba extracts studied with microbial test system (MTS)

“…To circumvent the limitations of the assays based on chemical mechanism to determine antioxidant synergistic effects, the MTS assay was adopted to measure the bioavailability behind synergism with some modification [27]. Bacteria were cultivated aerobically overnight in LB medium in shaking bed (37 °C, 120 rpm).…”

“…However, the observation in antioxidant synergistic effects of P. fruticosa combined with EGb is still not enough to guide in-depth pharmaceutical applications of P. fruticosa . This experiment carried on the modified and improved assay based on microbial test system (MTS) in our lab [27], focused on the physiological bioavailability to further confirm the synergistic effects of P. fruticosa combined with EGb and try to find specific combinations with least concentrations that exhibit synergistic effects. Those compounds may help to produce natural and safe antioxidants products in lower doses instead of synthetic antioxidants.…”