Oxidative stress is a well-known phenomenon arising from physiological and nonphysiological factors, defined by the balance between antioxidants and pro-oxidants. While the presence and uptake of antioxidants are crucial, the pro-oxidant effects have not received sufficient research attention. Several methods for assessing pro-oxidant activity, utilizing various mechanisms, have been published. In this paper, we introduce a methodology for the simultaneous determination of antioxidant and pro-oxidant activity on a single microplate in situ, assuming that the FRAP method can measure both antioxidant and pro-oxidant activity due to the generation of pro-oxidant Fe²⁺ ions in the Fenton reaction. Systematic research using this rapid screening method may help to distinguish between compounds with dominant antioxidant efficacy and those with dominant pro-oxidant effects. Our preliminary study has revealed a dominant pro-oxidant effect for compounds with a higher number of oxygen heteroatoms, especially sp2 hybridized compounds (such as those containing keto groups), such as flavonoids and plant extracts rich in these structural types. Conversely, catechins, carotenoids, and surprisingly, extracts from birch leaves and chestnut leaves have demonstrated dominant antioxidant activity over pro-oxidant. These initial findings have sparked significant interest in the systematic evaluation of a more extensive collection of compounds and plant extracts using the developed method.

POM analysis and related approaches are significant tools based on calculating various physico-chemical properties and predicting biological activity, ADME parameters, and toxicity of a molecule. These methods are used to evaluate a molecule’s potential to become a drug candidate. Avenanthramides (AVNs) are promising secondary metabolites specific to Avena spp. (oat). They comprise the amides of anthranilic acid linked to various polyphenolic acids with or without post-condensation molecule transformation. These natural compounds have been reported to exert numerous biological effects, including antioxidant, anti-inflammatory, hepatoprotective, antiatherogenic, and antiproliferative properties. To date, almost 50 various AVNs have been identified. We performed a modified POM analysis of 42 AVNs using MOLINSPIRATION, SWISSADME, and OSIRIS software. The evaluation of primary in silico parameters revealed significant differences among individual AVNs, highlighting the most promising candidates. These preliminary results may help coordinate and initiate other research projects focused on particular AVNs, especially those with predicted bioactivity, low toxicity, optimal ADME parameters, and promising perspectives.

Background: The balance between antioxidants and pro-oxidants plays a significant role in the context of oxidative stress, influenced by both physiological and non-physiological factors. Objectives: In this study, 18 prescribed antibiotics (including doxycycline hydrochloride, tigecycline, rifampicin, tebipenem, cefuroxime, cefixime, potassium clavulanate, colistin, ampicillin, amoxicillin, amikacin, nalidixic acid, azithromycin, pipemidic acid trihydrate, pivmecillinam, aztreonam, fosfomycin sodium, and ciprofloxacin) were subjected to simultaneous determination of antioxidant and pro-oxidant potential to assess if pro-oxidant activity is a dominant co-mechanism of antibacterial activity or if any antibiotic exhibits a balanced effect. Methods: This study presents a recently developed approach for the simultaneous assessment of antioxidant and pro-oxidant potential on a single microplate in situ, applied to prescribed antibiotics. Results: Ten antibiotics from eighteen showed lower antioxidant or pro-oxidant potential, while five exhibited only mild potential with DPPH50 values over 0.5 mM. The pro-oxidant antioxidant balance index (PABI) was also calculated to determine whether antioxidant or pro-oxidant activity was dominant for each antibiotic. Surprisingly, three antibiotics—doxycycline hydrochloride, tigecycline, and rifampicin—showed significant measures of both antioxidant and pro-oxidant activities. Especially notable was tebipenem, a broad-spectrum, orally administered carbapenem, showed a positive PABI index ratio, indicating a dominant antioxidant over pro-oxidant effect. Conclusions: These findings could be significant for both therapy, where the antibacterial effect is enhanced by radical scavenging activity, and biotechnology, where substantial pro-oxidant activity might limit microbial viability in cultures and consequently affect yield.

The threatening phenomenon of antibiotic failure in the future determines the intensive research of antibacterial active compounds, which are promising candidates as antibiotics. Quinolines, with only the representative in clinical practice being Nitroxoline^TM, are, in addition to being effective beta-lactams, macrolides, tetracyclines, and other antibiotic categories, forgotten antibiotics. The antibacterial efficiency of Nitroxoline^TM and 2-aminoquinolin-8-ol on eight selected highly resistant bacterial species that are the most problematic (Klebsiella ssp., Enterococcus ssp., Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus) could lead to higher solubility and thus bioavailability and increased antibacterial effects. In the first phase, the basic salts of Nitroxoline^TM, with sodium hydroxide, benzylamine, 4-(aminomethyl)pyridine, and other primary amines, were synthesized. In the second phase, the corresponding acidic salts of 2-aminoquinolin-8-ol were synthesized with the following acids: oxalic acid, pyrazine-2,3-dicarboxylic acid, chelidonic acid, quinaldic acid, 3,5-dinitrosalycilic acid, quinoline-2-carboxylic acid, quinoline-3-carboxylic acid, kynurenic acid, and xanthurenic acid. Nitroxoline^TM and 2-aminoquinolin-8-ol both demonstrated moderate antibacterial effects, with the average value for the eight mentioned bacterial strains being 16 mg/L (84 μM) and 50 mg/L (301 μM), respectively. The synthetized salts of both quinolinols demonstrated significantly higher solubility and slightly increased antibacterial activity. The identity and purity of the prepared products were determined by NMR and IR spectroscopy. The MW values of both quinolinols are relatively low and offer better use of the largest molecule limit, defined by Lipinski’s rule of five at 500 g/M. The options of amines and acids offer the achievement of quaternary salts with improved antibacterial activity.

Oxidative stress reflects an imbalance between pro-oxidants and antioxidants arising from physiological or environmental factors. Here, we applied our previously developed in situ microplate method for the simultaneous determination of antioxidant and pro-oxidant activities to compounds produced by plant cell cultures in vitro. The primary aim was to evaluate the added value of these compounds, which are widely used as additives in food, cosmetic, and pharmaceutical products. The secondary aim was to assess whether a predominance of pro-oxidant activity could limit their biotechnological production. Thirty-three compounds known to be produced by in vitro cultures (polyphenolic acids, flavonoids, quinones, alkaloids, etc.) were tested, and the pro-oxidant–antioxidant balance index (PABI) was calculated. Sixteen compounds showed measurable activities with DPPH₅₀/FRAP₅₀ values below 2 mM. Within this set, rosmarinic acid exhibited pronounced pro-oxidant behavior, whereas gallic acid, chlorogenic acid, and the anthocyanin cyanidin showed higher antioxidant potency and favorable PABI values. Such compounds may deliver added benefits when incorporated into food or cosmetic products and are unlikely to limit production in cell culture.