Biological activity of boron-containing compounds (BCCs) has been well-known. Growing interest and numerous applications for BCCs have been reported. Boron and boron-containing acids show low acute toxicity in mammals but data on halogenated boroxine (HB) - dipotassium-trioxohydroxytetrafluorotriborate, K 2 (B 3 O 3 F 4 OH) acute toxicity have not been reported before. This compound, characterized as a potential therapeutic for skin changes, exhibits no observable genotoxicity in doses lower that 0.1 mg/ml in vitro and 55 mg/kg in vivo. It has also been confirmed as an antitumour agent both in vitro and in vivo as well as an inhibitor of enzymes involved in antioxidant mechanisms. The aim of this study was to assess the acute toxicity of HB and to determine the maximum tolerated dose as well as a dose free of any signs of toxicity in different test organisms. Acute toxicity of HB was tested in Sprague-Dawley and Wistar rats and BALB/c mice after single parenteral application of different doses. We determined doses free of any sign of toxicity and LD 50 after single dose administration. LD 50 of HB ranges from 63 to 75 mg/kg in different test models, meaning that HB shows moderate toxicity.

Apoptosis induction is a promising approach in targeting tumor cells. As halogenated boroxine (HB) shows antitumor activity, but its mechanism of action in hematological tumors remains unclear, in this study, we aimed to analyze apoptosis triggering in normal and UT‐7 leukemia cells by HB. Methods for assessing cell viability and cytotoxicity, apoptosis detection, relative expression of 84 apoptosis‐associated genes and BCL‐2, and functional analysis were applied. Pronounced HB activities in inhibition of cell viability, cytotoxicity, and apoptosis induction with measurable differences between tumor and normal cells were found. HB modulated the expression of 21 genes, predominantly downregulated the antiapoptotic genes in leukemia. The functional association revealed HB's impact on inhibition of NF‐κB signaling pathway. BCL‐2 expression decreasing was found only in UT‐7 leukemia. This study identified HB as an apoptosis inducer affecting leukemia but not normal cells considering mechanisms of selective activity that may be a great advantage of HB applications.

Abstract Halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate, K2[B3O3F4OH] (boroxine) was previously shown to be very effective in inhibition of several carcinoma cell lines, including the skin cancer. Here, we investigated its antimicrobial potential by targeting the multidrug-resistant opportunistic pathogens associated with skin and wound infections. The antimicrobial testing against eleven bacterial and four fungal species revealed good activity of boroxine against pathogenic filamentous fungi Penicillium funiculosum and Aspergillus niger (MIC50 64 and 128 µg/ml), and a moderate bioactivity against the yeast Candida albicans (MIC50 512 µg/ml). Among the tested multidrug-resistant bacteria, the best antibacterial effect, stable over a 24-h period, was observed against the methicillin-resistant Staphylococcus aureus strain (MRSA) at MIC of 1024 µg/ml. The atomic force microscopy (AFM) used to investigate the morphology of S. aureus cells revealed indentations on its cell envelope after the boroxine exposure. These results show that in addition to the antitumor effect, boroxine exerts wide spectrum antimicrobial activity, thus may help preventing the development of skin and wound-related opportunistic infections.

Abstract Plant bioflavonoids are widely present in the human diet and have various protective properties. In this study, we have demonstrated the capacity of delphinidin and luteolin to increase human telomerase reverse transcriptase (hTERT) expression level and act as protective agents against halogenated boroxine-induced genotoxic damage. Halogenated boroxine K2(B3O3F4OH) (HB), is a novel compound with potential for the treatment of both benign and malignant skin changes. In vivo and in vitro studies have confirmed the inhibitory effects of HB on carcinoma cell proliferation and cell cycle progression as well as enzyme inhibition. However, minor genotoxic effects of HB are registered in higher applied concentrations, but those can be suppressed by in vitro addition of delphinidin and luteolin in appropriate concentrations. Fresh peripheral blood samples were cultivated for 72 h followed by independent and concomitant treatments of HB with luteolin or delphinidin. We analyzed the differences in relative hTERT expression between series of treatments compared with controls, which were based on normalized ratios with housekeeping genes. The obtained results have shown that selected bioflavonoids induce upregulation of hTERT that may contribute to the repair of genotoxic damage in vitro.

It is known that oxidoreductase is responsible for the regulation of oxidative stress in organisms, and pathological changes occur within the cell in the form of accumulation or lack of superoxide and peroxide radicals if the oxidoreductase activity is disturbed. Currently, the development of drugs that target the affected cells while leaving healthy cells unaffected is of great interest. The action of potential drugs is based on the inhibition / activation of oxidoreductase. In this work, we studied the electrochemical parameters of superoxide dismutase as well as the action of the potential drug of boroxine - dipotassium trioxohydroxytetrafluorotriborate (K2[B3O3F4OH]) as a target therapeutic for enzyme activity. Electrochemical tests were carried out in a classical three-electrode system using cyclic voltammetry and chronoamperometry techniques, and the obtained results were presented in the form of the kinetic parameters with the maximum value of the current obtained when the solution was saturated with the substrate (Imax) and the Michaelis-Menten constant (Km). K2[B3O3F4OH] was proven to be a reversible inhibitor, and the obtained Imax without inhibitor value of 0.014 mM and Km = 12.09 mM. The results from the Lineweaver - Burk diagram show that the inhibition is a partial noncompetitive inhibition type.

Our previous in vitro and in vivo studies on standard tumor cell lines: mammary adenocarcinoma 4T1, melanoma B16F10, and squamous cell carcinoma SCCVII have demonstrated that dipotassium-trioxohydroxytetrafluorotriborate, K 2 [B 3 O 3 F 4 OH], affects the growth of cancer cells. Based on indicative results of its anticancer activity, that are comparable to the standard cytostatic 5-fluorouracil, we decided to analyze the antioxidant capacity of K 2 [B 3 O 3 F 4 OH]. In our research, we include two other simpler representatives of the boroxine family compounds: trimethoxyboroxine and t rimethylboroxine , which are commercially available. The study objective is to explore the possibility of similar behavior within the same class of boron compounds, that is, to examine the activity of K 2 [B 3 O 3 F 4 OH] compared to simpler representatives of the same family of compounds. On the one hand, K 2 [B 3 O 3 F 4 OH], theoretically has the ability to exchange electrons in the extinction of reactive radicals, since two boron atoms are sp3-hybridized and use electrons from the inner shell. On the other hand, trimethoxyboroxine, and trimethylboroxine, in theory, should not exchange electrons. However, recent studies indicate the potential for the boron atom to act like carbon and participate in the exchange of protons. The study used the standard laboratory method of 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assay. The selected boroxines were treated with a DPPH radical at a temperature of 35° C in various concentrations, and with a reaction time of one hour. Results of the DPPH test show an extremely weak antioxidant capacity exists for all investigated boroxines. When K 2 [B 3 O 3 F 4 OH] was tested at high concentrations, instead of decreased color in the DPPH radicals, there was an increase in absorbance readings, which could mean that this compound acts as a pro-oxidant at higher concentrations. Future research is recommended to examine the length of reaction times needed, and whether a change in the reaction conditions would boost the antioxidant capacity of K 2 [B 3 O 3 F 4 OH]. Finally, future research could test the hypothesis that K 2 [B 3 O 3 F 4 OH], in the absence of the expected antioxidant activity, acts as a pro-oxidant.

In this study, boroxine derivative (K2[B3O3F4OH]) was tested as an inhibitor of horseradish peroxidase (HRP) by spectrophotometric and electrochemical methods. The activity of horseradish peroxidase was first studied under steady-state kinetic conditions by a spectrophotometric method which required the use of guaiacol as a second substrate to measure guaiacol peroxidation. The results of this method have shown that, by changing the concentration of guaiacol as the literature suggests, a different type of inhibition is observed than when changing the concentration of hydrogen peroxide as the substrate. This suggests that guaiacol interferes with the reaction in some way. The electrochemical method involves direct electron transfer of HRP immobilized in Nafion nanocomposite films on a glassy carbon (GC) electrode, creating a sensor with an electro-catalytic response to the reduction of hydrogen peroxide. The electrochemical method simplifies kinetic assays by removing the requirement of reducing substrates.

Abstract The cytotoxic activity of phenylboroxine acid was evaluated in vitro on mouse mammary adenocarcinoma 4T1, mouse squamous cell carcinoma SCCVII, hamster lung fibroblast V79 and mouse dermal fibroblasts L929 cell lines. The cytotoxic effects were dose dependent for all tested tumour and non-tumour cell lines. Under in vivo conditions, three application routes of phenylboronic acid were studied: intra-peritoneal (i.p.), intra-tumour (i.t.) and per-oral. After tumour transplantation in syngeneic mice, phenylboronic acid was shown to slow the growth of both tumour cell lines (4T1 and SCCVII) compared with the control. The inhibitory effects were pronounced during the application of phenylboronic acid. For both tested tumour cell lines, the most prominent antitumour effect was obtained by intraperitoneal administration, followed significantly by oral administration.

Recently research shows that horseradish peroxidase, HRP, when combined with other compounds, is highly reactive toward different human tumour cells and that better understanding of catalytic mechanism and inhibition HPR could lead to a new targeted cancer therapy. Thus, the inhibition of HRP activity by dipotassium-trioxohydroxytetrafluorotriborate K2[B3O3F4OH] was investigated for possible explanation of previously observed antitumour activities of this promising drug. HRP activity was studied under steady-state kinetic conditions by a spectrophotometric method. In the absence of the inhibitor values of = 0.47 mM and = 0.34 mM min−1, respectively, were determined. The hydrogen peroxide H2O2 kinetic measurements show a competitive inhibition with the inhibition constant = 2.56 mM. The activation energy values were found to be very similar for both reactions; in the absence of inhibitor activation energy was 17.7 kJ mol−1 and in the presence of inhibitor activation energy was 16.3 kJ mol−1. The values of Arrhenius constants were found to be different; = 4.635 s−1 was measured in the absence of inhibitor while in the presence of inhibitor Arrhenius constant was 1.745 s−1 showing that K2[B3O3F4OH] initiates conformational change in the structure of the HRP and subsequently reduces its activity.

Non-small cell lung cancer has been shown to be resistant to many forms of chemotherapy and is amongst the deadliest cancers worldwide. The antiproliferative effects of halogenated boroxine K2(B3O3F4OH), have been confirmed in multiple cancer cell lines including melanoma and breast cancer. The potential for this chemical treatment on non-small cell lung cancer cells was studied and the lower threshold concentration with the clear biological effect of halogenated boroxine, was determined. Appling MTT assays and the relative gene expression analysis of two genes of interest, RRBP1 and PER1, novel knowledge on the biological potential of halogenated boroxine (HB) was gained, but did not lead to biological explanations of the mechanisms of halogenated boroxine activity. The results of MTT assay showed a significant HB effect on non-small cell lung cancer in concentration of 0.5 mg/mL, while relative expression levels of RRBP1 and PER1 did not significantly differ regardless the concentration applied.

Abstract Recently it was found that dipotassium-trioxohydroxytetrafluorotriborate, K2(B3O3F4OH), is a potent and highly specific inhibitor of precancerous cell processes. We conducted gene expression profiling of human melanoma cells before and after treatment with two concentrations (0.1 and 1 mM) of this boron inorganic derivative in order to assess its effects on deregulation of genes associated with tumor pathways. Parallel trypan blue exclusion assay was performed to assess the cytotoxicity effects of this chemical. Treatment with K2(B3O3F4OH) induced a significant decrease of cell viability in melanoma cellline at both tested concentrations. Furthermore, these treatments caused deregulation of more than 30 genes known as common anti-tumor drug targets. IGF-1 and hTERT were found to be significantly downregulated and this result may imply potential use of K2(B3O3F4OH) as an inhibitor or human telomerase and insulin-like growth factor 1, both of which are associated with various tumor pathways.