Evaluation of the effects of Zinc on the chemical composition and biological activity of basil essential oil by using Raman spectroscopy

The present study is performed to evaluate the effect of different concentrations of Zn as fertilizer on the chemical composition of basil (Ocimum basilicum) essential oil and its biological activity including antioxidant and antifungal activities. For this purpose, Raman spectroscopy along with GC-MS and antifungal assays are employed. Moreover, the effect of Zn is also determined on the vegetative growth and essential oil yield. The treatment with 0.09 mg/L of Zn showed maximum vegetative growth (0.24 ± 0.02 kg plant weight and 0.31 ± 0.03 m plant height) while the treatment with 0.15 mg/L of Zn revealed highest essential oil yield (0.48 ± 0.019%) as compared to 0.28 ± 0.005% for control. All essential oils exhibited significant total phenolic contents, total flavonol contents, antioxidant activity measured by hydrogen peroxide scavenging, inhibition of linoleic acid oxidation and DPPH free radical scavenging and Ferric reducing antioxidant power assay Antifungal activity of essential oils was performed by disc diffusion assay against Aspergillus niger and Penicillium notatum strains. The results of antifungal activity showed that essential oils isolated after treatment of 0.095 mg/L concentration of Zn fertilizer exhibited maximum antifungal activity. Chemical compositions of isolated essential oils were determined by Gas Chromatography-Mass spectrometry (GC-MS) and Raman spectroscopy. The results of the GC-MS and Raman spectroscopy have revealed that the linalool is found to be as a major chemical compound in Ocimum basilicum essential oil. Moreover, Raman spectroscopy has identified the effect of the Zn on the concentration of the biological components present in essential oil showing that highest concentration of linalool found in the essential oil obtained from the basil plants which were given 0.095 mg/L of Zn fertilizer treatment that might be responsible for the maximum biological activities of this essential oil.