RESUMEN
BACKGROUND: Smokeless tobacco (SLT) is traditionally used in Middle East countries. The several toxic constituents with potential carcinogenicity make it a serious human health risk. Literature regarding their effects on cardiac and cancer disease is lacking in Saudi Arabia. OBJECTIVE: This study was conducted to investigate the adverse effect of 11 different samples of widely used SLT varieties from the Tabuk region - Saudi Arabia, on Nitric Oxide (NO) level and their potential risk on cardiovascular health, etiology and/or progression of cancers. METHODS: Samples were collected from Tabuk, KSA and analyzed by the GC-MS technique. Nitric oxide inhibition was performed using J774.2 macrophages by the Griess method. The retrieved crystallized structure of human inducible nitric oxide synthase (iNOS) from Brookhaven Protein Data Bank Repository PDB I.D: 3E7G with 2.20Å resolution was further prepared by structure using the MOE.2019 tool. The compounds abstracted from 11 different Shammah varieties were sketched by the MOE-Builder tool. Minimization for both receptor and compounds was performed via AMBER99 and MMFF99X force field implemented in MOE. RESULTS: Nine samples (4 - 11) showed a potent suppressive effect on NO production with IC50 values ranging between (16.9-20.4 µg/mL), respectively. The samples (1 & 2) exhibited a moderate level of inhibition with IC50 ranging between 33.2 and 57.4 µg/mL, respectively. Interestingly, sample 4 consisting of compounds (13-15, 19-26, 28) that mostly belongs to the group fatty acid ester and phthalic acid ester showed the most potent suppressive effect. Molecular docking results revealed that the current local SLT constituents presented noticeable potency in different extract samples. CONCLUSION: Variable suppressive effects on NO were detected in the current SLT samples, where sample 4 was the most potent among all. The extract of the latter exhibited molecular interaction with the first shell amino acid residues of Inducible nitric oxide synthase (iNOS), which may anchor the plasticity and selectivity of the compounds present in it. The samples (4 -11) showed a potent inhibitory effect on the NO, where compound 26 (Phthalic acid ester) is common, and its adequate concentration may account for augmented biological activity. These results may effectively highlight their adverse effects on cardiovascular health and etiology and/or progression of cancer and may help in strengthening the social and governmental efforts in minimizing the use of these substances.