Oxidation reactions of hydroxy naphthoquinones: Mechanistic investigation by LC-Q-TOF-MS analysis

Selective accumulation of pharmaceutical residues from 6 different soils by plants: a comparative study on onion, radish, and spinach

The accumulation of six pharmaceuticals of different therapeutic uses has been thoroughly investigated and compared between onion, spinach, and radish plants grown in six soil types. While neutral molecules (e.g., carbamazepine (CAR) and some of its metabolites) were efficiently accumulated and easily translocated to the plant leaves (onion > radish > spinach), the same for ionic (both anionic and cationic) molecules seems to be minor to moderate. The maximum accumulation of CAR crosses 38,000 (onion), 42,000 (radish), and 7000 (spinach) ng g-1 (dry weight) respectively, in which the most majority of them happened within the plant leaves. Among the metabolites, the accumulation of carbamazepine 10,11-epoxide (EPC - a primary CAR metabolite) was approximately 19,000 (onion), 7000 (radish), and 6000 (spinach) ng g-1 (dry weight) respectively. This trend was considerably similar even when all these pharmaceuticals applied together. The accumulation of most other molecules (e.g., citalopram, clindamycin, clindamycin sulfoxide, fexofenadine, irbesartan, and sulfamethoxazole) was restricted to plant roots, except for certain cases (e.g., clindamycin and clindamycin sulfoxide in onion leaves). Our results clearly demonstrated the potential role of this accumulation process on the entrance of pharmaceuticals/metabolites into the food chain, which eventually becomes a threat to associated living biota.

Qualitative and Quantitative Analyses of the Chemical Components of Peels from Different Pomelo Cultivars (Citrus grandis [L.] Osbeck) Based on Gas Chromatography-Mass Spectrometry, Ultraperformance Liquid Chromatography-Q-Exactive Orbitrap-MS, and High-Performance Liquid Chromatography-Photodiode Array Detection

The volatile and nonvolatile phytochemicals in peels of 5 major pomelo cultivars (including Citrus grandis cv. Yuhuanyou, C. grandis cv. Liangpingyou, C. grandis cv. Guanximiyou, C. grandis cv. Duweiwendanyou, and C. grandis cv. Shatianyou) from 11 places in China were characterized. First, 194 volatile compounds in pomelo peels were identified by gas chromatography-mass spectrometry (GC-MS). Of these, 20 major volatile compounds were subjected to cluster analysis. The heatmap indicated that the volatile compounds in peels of C. grandis cv. Shatianyou and C. grandis cv. Liangpingyou were different from those in other varieties, while there was no difference among C. grandis cv. Guanximiyou, C. grandis cv. Yuhuanyou, and C. grandis cv. Duweiwendanyou from different origins. Second, 53 nonvolatile compounds were identified in pomelo peels by ultraperformance liquid chromatography-Q-exactive orbitrap tandem MS (UPLC-Q-exactive orbitrap-MS), of which 11 components were detected for the first time. Third, six major nonvolatile compounds were quantitatively analyzed with high-performance LC-photodiode array detection (HPLC-PDA). Combining the results of HPLC-PDA and the heatmap, 6 nonvolatile compounds in 12 batches of pomelo peel were well separated among varieties. Comprehensive analysis and identification of chemical components in pomelo peels are of great significance for their further development and utilization.

Analysis of the chemical components of pomelo peels (Citrus grandis [L.] Osbeck) from different cultivars by using supercritical CO2 fluid extraction and UHPLC-MS/MS

Five pomelo cultivars (i.e., Citrus grandis cv. Shatianyou, Citrus grandis cv. Guanximiyou, Citrus grandis cv. Yuhuanyou, Citrus grandis cv. Duweiwendanyou and Citrus grandis cv. Liangpingyou) from different origins in China were selected to analyse their components by using supercritical CO₂ fluid extraction coupled with ultra-high-performance liquid chromatography tandem mass spectrometry. A total of 45 compounds were identified in the supercritical CO₂ fluid extracts of the pomelo peels from the five cultivars. These compounds included 8 flavonoids, 18 coumarins, 4 organic acids, 3 aldehydes and 12 other compounds, which were identified using the obtained MS data and by comparison with commercial standards, Orbitrap Chinese Traditional Medicine Library and previous literature. Twenty-five of the identified compounds were detected for the first time in the pomelo peel extracts. Results suggested that the pomelo peels of C. grandis cv. Shatianyou contained the most natural chemical compositions. The pooled result may offer a scientific evidence for further development and utilisation of pomelo peels and a route for screening appropriate varieties for various demands. This article is protected by copyright. All rights reserved.

Oxidative Degradation of Pharmaceutical Waste, Theophylline, from Natural Environment

The elimination of organic contaminants from natural resources is extremely important to ensure their (re-)usability. In this report, the degradation of a model pharmaceutical compound, theophylline, is compared between natural and laboratory-controlled environments. While the concentration of H2O2 variably affected the degradation efficiency (approximately from 8 to 20 min for complete degradation) in the photo-irradiation experiments, the inorganic compounds (NaNO3, KH2PO4 and ZnSO4) present in the medium seemed to affect the degradation by scavenging hydroxyl radicals (•OH). The end-product studies using high-resolution mass spectrometry (HRMS) ruled out the involvement of secondary radicals in the degradation mechanism. The quantitative calculation with the help of authentic standards pointed out the predominant role of hydroxylation pathways, especially in the initial stages. Although a noticeable decline in the degradation efficiency was observed in river water samples (complete degradation after 25 min with an approximately 20% total organic carbon (TOC) removal), appreciable TOC removal (70%) was eventually achieved after prolonged irradiation (1 h) and in the presence of additional H2O2 (5 times), revealing the potential of our technique. The results furnished in this report could be considered as a preliminary step for the construction of •OH-based wastewater treatment methodologies for the remediation of toxic pollutants from the real environment.

Sonochemical degradation of benzenesulfonic acid in aqueous medium

Degradation of benzenesulfonic acid (BSA), the simplest aromatic sulfonic acid with extreme industrial importantance, by sonochemically generated hydroxyl radical (OH) have been thoroughly investigated. A reasonable reduction (∼50%) in the total organic carbon (TOC) was achieved only after prolonged irradiation (∼275 min, 350 kHz) of ultrasound, although a short irradiation of less than an hour is enough to degrade significant amount of BSA. The degradation efficiency of ultrasound has been reduced in lower and extremely higher frequencies, and upon increasing the pH. An irregular, but continuous, release of sulfate ions was also observed. Further, the release of protons upon the oxidation of BSA consistently reduces the experimental pH to nearly 2. High resolution mass spectrometric (HRMS) analyses reveals the formation of a number of aromatic intermediates, including three mono (I_a-c) and two di (II_a&b) hydroxylated BSA derivatives as the key products in the initial stages of the reaction. Pulse radiolysis studies revealed the generation of hydroxycyclohexadienyl-type radicals, characterized by absorption bands at 320 nm (k₂ = (7.16 ± 0.04) × 10⁹ M^-1 s^-1) and 380 nm, as the immediate intermediates of the reaction. The mechanism(s) leading to the degradation of BSA under sonolytic irradiation conditions along with the effect of various factors, such as the ultrasound frequency and reaction pH, have been explained in detail. The valuable mechanistic aspects obtained from our pulse radiolysis and HRMS studies are essential for the proper implementation of sonochemical techniques into real water purification process and, thus, receives extreme environmental relevance.

Identification of position isomers by energy-resolved mass spectrometry

This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals ((●)OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by (●)OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho > meta > para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M - H](-) towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M - H](-) molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods.