The impact of differential lignin S/G ratios on mutagenicity and chicken embryonic toxicity

In vitro and in silico evaluation of the design of nano-phyto-drug candidate for oral use against Staphylococcus aureus

Onopordum acanthium is a medicinal plant with many important properties, such as antibacterial, anticancer, and anti-hypotensive properties. Although various studies reported the biological activities of O. acanthium, there is no study on its nano-phyto-drug formulation. The aim of this study is to develop a candidate nano-drug based on phytotherapeutic constituents and evaluate its efficiency in vitro and in silico. In this context, poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) of O. acanthium extract (OAE) were synthesized and characterized. It was determined that the average particle size of OAE-PLGA-NPs was 214.9 ± 6.77 nm, and the zeta potential was -8.03 ± 0.85 mV, and PdI value was 0.064 ± 0.013. The encapsulation efficiency of OAE-PLGA-NPs was calculated as 91%, and the loading capacity as 75.83%. The in vitro drug release study showed that OAE was released from the PLGA NPs with 99.39% over the 6 days. Furthermore, the mutagenic and cytotoxic activity of free OAE and OAE-PLGA-NPs were evaluated by the Ames test and MTT test, respectively. Although 0.75 and 0.37 mg/mL free OAE concentrations caused both frameshift mutation and base pair substitution (p < 0.05), the administered OAE-PLGA NP concentrations were not mutagenic. It was determined with the MTT analysis that the doses of 0.75 and 1.5 mg/mL of free OAE had a cytotoxic effect on the L929 fibroblast cell line (p < 0.05), and OAE-PLGA-NPs had no cytotoxic effect. Moreover, the interaction between the OAE and S. aureus was also investigated using the molecular docking analysis method. The molecular docking and molecular dynamics (MD) results were implemented to elucidate the S. aureus MurE inhibition potential of OAE. It was shown that quercetin in the OAE content interacted significantly with the substantial residues in the catalytic pocket of the S. aureus MurE enzyme, and quercetin performed four hydrogen bond interactions corresponding to a low binding energy of -6.77 kcal/mol with catalytic pocket binding residues, which are crucial for the inhibition mechanism of S. aureus MurE. Finally, the bacterial inhibition values of free OAE and OAE-PLGA NPs were determined against S. aureus using a microdilution method. The antibacterial results showed that the inhibition value of the OAE-PLGA NPs was 69%. In conclusion, from the in vitro and in silico results of the nano-sized OAE-PLGA NP formulation produced in this study, it was evaluated that the formulation may be recommended as a safe and effective nano-phyto-drug candidate against S. aureus.

Syringol, a wildfire residual methoxyphenol causes cytotoxicity and teratogenicity in zebrafish model

Natural toxicants, particularly methoxy phenols (MPs) generated by wildfire lignin, can accumulate in the environment, and cause serious health hazards in living organisms. Although the toxicity of MPs such as guaiacol and catechol has recently been described, there is minimal evidence of ecotoxicological effects of syringol. As a result, this study focuses on determining the toxicity by evaluating the cytotoxic and teratogenic effects of syringol in vitro and in vivo in human embryonic kidney (HEK-293) cells and zebrafish embryos, respectively. The ecotoxicity of syringol was predicted to be 63.8 mg/L using the ECOSAR (ECOlogical Structure Activity Relationship) prediction tool, and molecular docking analysis was used to determine the interaction and binding affinities of syringol with human apoptotic proteins in silico. In HEK-293 cells, exposure of syringol (0.5-2 mg/L) has induced cytotoxicity in a concentration-dependent manner. In zebrafish larvae, exposure of syringol (0.5-2 mg/L) has induced dose-dependent embryo toxic effects (or growth abnormalities such as yolk sac edema, pericardial edema, skeletal abnormality, and hyperemia), and changes in growth morphometrics (head height, eye, yolk sac, and pericardial area, heart rate) in particular, the heart rate of larvae was found to be significantly decreased (p<0.001). After a 4-day experimental trial, the accumulated concentration of syringol in zebrafish larvae was confirmed both qualitatively (HPLC-MS - High Performance Liquid Chromatography-Mass spectrometry) and quantitatively (LC-QTOF-HRMS - Liquid Chromatography-Quadrupolar Time of Flight-High Resolution Mass spectrometry). The craniofacial abnormalities induced by syringol exposure (0.5-2 mg/L) were detected as anomalies in cartilaginous development and locomotor deficits using alcian blue staining and locomotor analyses, respectively. Significant increase in oxidative stress parameters (including reactive oxygen species generation, lipid peroxidation, superoxide dismutase, catalase, lactate dehydrogenase and nitric oxide production) (p<0.001) and substantial decrease in glutathione levels were observed (p<0.05) in syringol exposed zebrafish larvae through enzymatic analysis. Additionally, through acridine orange staining and gene expression analyses, syringol (2 mg/L) was found to activate apoptosis in zebrafish larvae. Considering the cytotoxic, embryotoxic (teratogenicity), and oxidative stress-related apoptotic effects of syringol in the zebrafish model, syringol has the potential to emerge as a potent environmental toxicant posing serious health hazards in many living systems; however, further research on its toxicological effects on the actual ecosystem and in higher animal models is required to confirm its consequences.

Reduced genotoxicity of lignin-derivable replacements to bisphenol A studied using in silico, in vitro, and in vivo methods

Bisguaiacols, lignin-derivable bisphenols, are considered promising and possibly safer alternatives to bisphenol A (BPA), but comprehensive toxicity investigations are needed to ensure safety. Most toxicity studies of BPA and its analogues have focused on potential estrogenic activity, and only limited toxicological data are available on other toxicity aspects, such as genotoxicity at low exposure levels. In this study, the genotoxicity of six lignin-derivable bisguaiacols with varying regioisomer contents and degrees of methoxy substitution was investigated using a multi-tiered method, consisting of in silico simulations, in vitro Ames tests, and in vivo comet tests. The toxicity estimation software tool, an application that predicts toxicity of chemicals using quantitative structure-activity relationships, calculated that the majority of the lignin-derivable bisguaiacols were non-mutagenic. These results were supported by Ames tests using five tester strains (TA98, TA100, TA102, TA1535, and TA1537) at concentrations ranging from 0.5 pmol/plate to 5 nmol/plate. The potential genotoxicity of bisguaiacols was further evaluated using in vivo comet testing in fetal chicken livers, and in addition to the standard alkaline comet assay, the formamidopyrimidine DNA glycosylase enzyme-modified comet assay was employed to investigate oxidative DNA damage in the liver samples. The oxidative stress analyses indicated that the majority of lignin-derivable analogues showed no signs of mutagenicity (mutagenic index < 1.5) or genotoxicity, in comparison to BPA and bisphenol F, likely due to the methoxy groups on the lignin-derivable aromatics. These findings reinforce the potential of lignin-derivable bisphenols as safer alternatives to BPA.

Effects of Drying Methods and Temperatures on the Quality of Chestnut Flours

The demand for chestnut flour is growing because of its use in gluten-free products. Previous studies have correlated the quality of chestnut flours to the drying temperature and technology applied. This work is a novel study on the role of the traditional drying method with a wood fire in a “metato” building for flour compared with a food dryer at 40 °C or 70 °C. The contents of antioxidants, total polyphenols and sugars were determined as well as the presence of toxic volatiles or aflatoxins. The flour, resulting from the traditional method, presented lower polyphenol content and antioxidant power compared to the others. The content of the sugars was similar to the flours obtained after drying with hot air, both at 40 °C and 70 °C. The toxic volatile molecules, furfural, guaiacol, and o-cresol, were found. There was no correlation between the aflatoxin content and the presence of damage in chestnut fruits. The traditional method should not be abandoned since it confers a pleasant smoky taste to the product, but it is necessary to regulate the level and steadiness of temperature. Future research needs to be directed to the quantification of harmful volatile compounds and their correlation with the quantity of smoke emitted by the wood fire.