Phytochemical Diversity, Classification and Antibacterial Activity of Some Medicinal Plant Species from Tabuk (Saudi Arabia)

The main objectives of this study were to investigate the intra-specific and inter-specific phytochemical diversity and classification of nine important medicinal plant species from Tabuk region (KSA), namely (Pulicaria undulata L., Pulicaria incisa Lam., Artemisia herba-alba Asso., Artemisia monosperma Delile, Artemisia judaica L. and Achillea fragrantissima Forssk. from Asteraceae family, Ducrosia flabellifolia Boiss. from Apiaceae family, Thymus vulgaris L. and Lavandula coronopifolia Poir. from Lamiaceae family); to evaluate the antibacterial potentials of the plant extracts, and to inspect the possible associations between phytochemical diversity and contents of different phytochemical classes with the antibacterial activities of plant extracts. GC/MS technique was used to identify phytochemicals in the plant extracts. The standard disk diffusion technique was used to conduct the antibiotic susceptibility against four pathogenic bacterial species (two Gram positive: Staphylococcus aureus and Bacillus subtilis and two Gram negative species: Pseudomonas aeruginosa and Escherichia coli. A total of 160 different phytochemicals belonging to 30 compound classes were separated and identified. A. fragrantissima had the highest phytochemical diversity and P. incisa had the lowest one. Phytochemical beta diversity was 6.2362. Ethanol outperformed other extraction solvents in terms of antibacterial activity, while Pulicaria undulata and T. vulgaris ranked highest among plants in this regard. Gram positive bacterial species were more sensitive to plant extracts compared to Gram negative species. Phytochemical diversity and antibacterial activity of plant extracts against E. coli and P. aeruginosa were positively correlative, terpenoid and benzene & substituted derivative contents exhibited significant (p<0.05) positive correlations with the antibacterial activity against E. coli, terpenoid contents also showed positive correlation with activity against P. aeruginosa; benzene & derivative showed positive correlation with activity against the rest of bacterial species,