Toxicity Profile, Phytochemical Composition, and Anti-scaling Properties of the Aqueous Extract of Ocimum basilicum L. Leaves as Novel Green and Cost-Effective Inhibitor: Experimental, MC/SAA and DFT Approach

Today, the prevention or reduction of scale formed in the water desalination plant, using non-toxic inhibitors, is an important challenge. In this respect, the present research work aims at contributing to the promotion of Ocimum basilicum L. (basil) plant as a source of green, low-cost, and efficient scale inhibitors. Before evaluating the anti-scaling performance of the O. basilicum leaves aqueous extract ( OBLAE ), a toxicity study was performed by subacute oral administration in rats, and the phytochemical composition was determined using phytochemical screening, quantitative tests, and high-performance liquid chromatography with diode-array detection (HPLC-DAD) analysis. A chemical approach is used to investigate the inhibition performance of basil extract against CaCO 3 scale through conductivity and LCGE technique at 25 °C. Then, the scale inhibition mechanism is studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). To support the experimental results, Density Functional Theory (DFT) calculations and the Monte Carlo (MC) simulation are performed. The subacute oral toxicity test of OBLAE in rats revealed no toxic effects at the doses investigated. A phytochemical study showed the presence of phenolics acids ( p -hydroxybenzoic, vanillic, caffeic, and rosmarinic acids) and flavonoids (naringenin, rutin, quercetin, and kaempferol) in OBLAE. The LCGE findings proved that OBLAE shows a better anti-scaling activity, with an effective concentration of 48 mg L −1 . This strong inhibition performance is mostly due to the chelation properties of the identified polyphenols in the extract. SEM micrographs and XRD diffractograms showed that the addition of a scale inhibitor results in an apparent change in the form and phases of scale. Furthermore, the adopted computational approach supports well the experimental outcomes. Hence, OBLAE could be valorized as a valuable source of green scale inhibitors at a low cost. Graphical Abstract