Deciphering the Toxicity of Polycyclic Aromatic Hydrocarbons on Eseinia Fetida as Model Soil Fauna

Abstract

Polycyclic aromatic hydrocarbons (PAHs) represent a pervasive class of environmental pollutants with adverse effects on ecosystems and human health. This study was designed to unravel the intricate tapestry of toxicity specifically on Eisenia fetida, a keystone species in terrestrial environments using in silico molecular approach. Four PAHs including Benzo [a] pyrene (CID_2336), Anthracene (CID_31423), Pyrene (CID_31423) and Fluoranthene (CID_9154) were selected based on their relative soil abundance and their complexity. Their toxicity due to physicochemical and bioactive properties was assessed using SwissADME. Their inhibitory effect on endo-1,4- glucanase (PDB ID: 3WC3) was also demonstrated using molecular docking analysis. Results on the physicochemical properties of the ligands indicated that anthracene (CID_8418) and benzo [a] pyrene (CID_2336) had the smallest (178.22 g/mol) and largest (252.32 g/mol) molecular weights respectively. The toxicity of PAHs is a function of their molecular weight and sizes. The outcomes also demonstrated the strong mutagenic and tumorigenic potential of each ligand. The remaining PAHs, with the exception of fluoranthene, are similarly extremely irritating when exposed. Furthermore, all of the compounds except for benzo [a] pyrene are not readily reproduced. The ligands are harmful even to human subjects, according to their pharmacokinetics. The results of a molecular docking analysis indicate that CID_2336, which fits into the active cavity of 3WC3 and is stabilized by seven electrostatic contacts, has the lowest free binding energy of -5.15 kcal/mol. The higher free binding energies of the remaining PAHs ranged from -4.63 kcal/mol to -4.31 kcal/mol. With the exception of CID_31423, which had only six electrostatic connections, all of the ligands were stabilized by seven electrostatic interactions. All of the ligands shared identical amino acid residues, with the exception of CID_8418 and CID_9154, which lacked Ser48 and Val122, respectively. According to these results, 3WC3 can be inhibited by all PAHs. Endo-1,4- glucanase is a key enzyme in the digestive and nutrition absorption processes of the earthworm, and its inhibition can have detrimental effects on the organism. The creation of PAHs carrier molecules is necessary to prevent the compounds’ negative effects on the worm population during remediation or composting activities.