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The objective of this research was to investigate the efficacy of deep eutectic solvents (DESs)to extract polyphenolic compounds from tomato pomace with the assistance of ultrasound. The phytochemical constituents of tomato pomace extracts (TPE) were verified with a combination of high-performance liquid chromatography coupled with diode array detection and tandem mass spectrometry (HPLC-DAD-MS) and FTIR analysis. The extracted phenolic compounds from tomato pomace were quantified by Folin-Ciocalteu method. The predominant components in tomato pomace extracts were phenolic acids and flavanols. Chlorogenic acid was detected as the main phenolic compound in tomato extracts. The redox behavior of tomato pomace extracts was evaluated by means of cyclic voltammetry. Antioxidant activities of the obtained extracts were determined using the DPPH and ABTS scavenging assays. The reduction capacity of the extracts was assessed using ferric reducing power (FRAP) and phosphomolybdenum (PM) assays. extracts with DESs are characterized by the highest level of antioxidant activity. Theoretical study based on quantum chemistry/molecular modeling were performed to confirm the antioxidants capacity of compounds of tomato pomace extracts. Quantum chemical descriptors such as the frontier orbital energies (EHOMO and ELUMO), the energy gap between EHOMOand ELUMO (ΔE), hardness, and electrophilicity index have been calculated and discussed. [ABSTRACT FROM AUTHOR]

The component profiles of apricot, grape, and black currant pomace extracts have been analyzed using HPLC coupled to diode-array detection and tandem mass spectrometry (HPLC-DAD-MS). The predominant components in grape, apricot, and black currant pomace extracts were phenolic acids and flavonols. The redox behavior of apricot, black currant, and grape pomace water extracts was evaluated by means of cyclic voltammetry. Also, individual substances mainly present in the extracts were analyzed. The results of electrochemical testing were compared to traditional chemical techniques of potassium ferricyanide reduction (FRAP) and phosphomolybdenum assay, and fair agreement was established. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assays were applied in order to estimate antioxidant activity. The reducing power of the grape extract was found to be higher than that of the apricot and black currant extracts in both potassium ferricyanide reduction (FRAP) and phosphomolybdenum methods. [ABSTRACT FROM AUTHOR]

Corrosion rate of mild steel in tap water during 4300 h was estimated by LPR and weight-loss methods coupled with OCP measurements. The LPR results were found to be overestimated compared to the weight-loss data within initial 2000 h of exposure. The electrochemical activity of the rust separated from the metal surface was studied by cycling voltammetry using a home-built powder graphite electrode. High redox currents corresponding to the initial 2000 h of exposure were detected. Rust composition was characterized with IR and XRD, and the highest amounts of electrochemically active β- and γ-FeOOH were again detected for the initial 2000 h. Current consumption in rust transformation processes during LPR measurement in the galvanostatic mode accounts for overestimation of the corrosion rate. The time dependence of rust electrochemical activity correlates with OCP variation with time. During initial 2000 h, OCP values are shifted by 50 mV to cathodic side. For the period of a higher rust electrochemical activity, the use of a reduced B is suggested to increase accuracy of LPR technique in tap water. [ABSTRACT FROM AUTHOR]