Effect of cold plasma and elicitors on bioactive contents, antioxidant activity and cytotoxicity of Thai rat‐tailed radish microgreens

Abstract

BACKGROUND: Raphanus sativus var. caudatus or Thai rat-tailed radish (RTR) contains glucosinolates and isothiocyanates with chemopreventive effects; however, only mature plants have been investigated to date. Thus, the present study aimed to determine isothiocyanates, phenolic compounds and flavonoid compounds, antioxidant activity, cytotoxicity, and antiproliferative activity of RTR microgreens grown from seeds treated with cold plasma (21 kV for 5 min), organic elicitor (160 mmol L −1 NaCl, 10 mmol L −1 CaCl 2 or 176 mmol L −1 sucrose) or both in combination. Seeds were germinated on vermiculite and sprayed with deionized water or elicitor for 7 days before harvest. RESULTS: Cold plasma had insignificant effect on growth, whereas NaCl and CaCl 2 increased fresh weight. Plasma with CaCl 2 led to the highest total isothiocyanate (ITC) content [1.99 g kg −1 dry weight (DW)] in RTR microgreens containing raphasatin as the only ITC detected. Plasma treatment gave the highest total phenolic content (7.56 mg gallic acid equivalents g −1 DW), antioxidant activity from a 2,2-diphenyl-1-picrylhydrazyl assay (7.70 mg trolox equivalents g −1 DW) and ferric reducing antioxidant power assay (21.72 mg Fe 2+ g −1 DW). Microgreen extracts from plasma showed an IC 50 value of 29.28 and 13.83 ∼g mL −1 towards MCF-7 and HepG2, respectively, with inhibitory properties on matrix metalloproteinase (MMP)-2 and MMP-9 proteins. Plasma enhanced Bax and Caspase-3 gene expression but reduced Bcl-2 and MMP-9 expression, indicating activation of apoptosis. CONCLUSION: Cold plasma shows promise as an innovative tool to enhance bioactive compounds with chemopreventive benefits in microgreens.

Effect of Pre-soaking Mustard Green Seeds Prior to Cold Plasma Treatment on Bioactive Aspects of Microgreens

“…The test group of PTPS seeds (100 seeds/treatment with triplicate) were presoaked overnight prior to plasma treatment for 5 min at 21 kV at the Faculty of Engineering Srinakharinwirot University, Nakhon Nayok, Thailand. 7 The control group was MG seeds without soaking and without plasma treatment. Both PTPS and control seeds were cultivated as previously done till harvest (7 days).…”

“…Both PTPS and control seeds were cultivated as previously done till harvest (7 days). 7 After a gentle cut 1 cm above vermiculite, the physiology of MG microgreen was measured and they were stored at -80°C until the next experiment.…”

“…The ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging methods were assessed according to the previous work. 7 The FRAP reagent (180 μL) was mixed with MG extract solution (20 μL) and incubated for 30 min. The absorbance at 593 nm was observed and iron (II) sulfate was used as a standard.…”

“…TPC and TFC were determined using previous methods. 7 The TPC was evaluated using a Folin-Ciocalteu colorimetric method. The reagent Folin-Ciocalteu (100 μL) was mixed with the MG microgreen extract (20 μL) and left for 1 min.…”

“…The PCR reaction was done using 2× Master Mix (OnePCR, GeneDirex, Taiwan) with added primers to five genes (Bax, Bcl-2, Caspase-3, MMP-9 and Beta-actin as reference gene). 7 The PCR products were analyzed using agarose gel electrophoresis with gel documentation and intensity measurements done with ImageJ software.…”