Phytochemical Study and Antibacterial Effects of Fraxinus angustifolia Vahl (Algeria): Experimental and Computational Investigations

Abstract

We investigated experimentally the composition of volatile isolates from the leaves and seeds of fraxinus angustifolia Vahl and their antimicrobial activity. The experimental work was supported by a theoretical study, using the Functional Density Theory. The calculations were performed at the B3LYP/6–31 g-d, p), in order to determine the structures of major volatile compounds and the different descriptors of reactivity and biological activity. The chemical composition of the volatile isolates obtained by hydrodistillation of the leaves and seeds are evaluated by the analytical method of gas chromatography-mass spectrometry (GC-MS). We found that the leaves are composed of abundant compounds, specifically, docosane methyl (30.2%), n-Pentacosane (28.5), α-cadinol (9.0%) and T-muurolol (5.9%). Moreover, the isolate from the seeds, is found to be mainly composed of α-cadinol (23.2%) and epi-methyljasmonate (34. 2%). Additionally, we perform antimicrobial activity tests on the volatile isolated using the zone of inhibition (agar disk-diffusion method) of four bacteria strains, mainly, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. The values of leaves range from 100 to 300 µg of volatile compounds, whereas for the seeds the values lie between 20 and 300 µg. Furthermore, antifungal susceptibility tests are conducted on two yeast strains: Saccharomyces cerevisiae and Candida albicans. The seeds have a better inhibition than the leaves, with 20 and 300 µg respectively. The chemical compositions of the volatile fractions of leaves and seeds are correlated with the antimicrobial results. The reactivity descriptors are calculated to determine stability and microbiological activity of the above compounds. The Isopimaradiene presents the higher microbiological activity and the most stable T-muurololis.