The main objectives of this study were to investigate the intraspecific 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, [a] Dr. A. A.

This study aims to investigate the anti‐parasite, anti‐oxidant activities, cytotoxicity and chemical contents of Rhynchosia memnonia var. memnonia and Sonchus oleraceus aerial parts. The study showed the efficacy of the ethanolic extracts of R. memnonia var. memnonia and S. oleraceus against Giardia lamblia. R. memnonia var. memnonia was a high effect of (76 %) at a concentration of 500 ppm after 72 h, while the highest result of the crude extract of S. oleraceus was (86 %) at the same concentration after 72 h. The antioxidant activity of S. oleraceus ethanolic crude extract showed high activity (72 %). At the same time, the ethanolic extract of R. memnoniavar. memnonia showed weak activity (36 %). This was done using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. The results of cytotoxicity testing revealed that the ethanolic extract of R. memnonia var. memnonia is highly toxic, while the toxicity was slight for the ethanolic extract of S. oleraceus used to brine shrimp. In addition, the cytotoxicity (MTT‐assay) of these plants′ ethanolic extracts against the normal Vero cell line verified the safety of the examined extracts with an IC50 less than 100 μg/ml. In order to detect the constituents of crude extracts, GC‐MS was used. The analysis revealed the presence of 22 compounds in the ethanolic extract of R. memnonia var. memnonia and eleven compounds in the S. oleraceus crude extract. From R. memnonia var. memnonia and S. oleraceus, the main compounds detected were n‐Hexadecadnoic acid and Lup‐20(29)‐en‐3b‐ol, respectively. Also, many other compounds were identified at low area percent from these extracts.

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Herbicidal effects of Prosopis juliflora (Sw.) (mesquite) leaf extract on seed germination and seedling development of the weed species Tribulus terrestris L. was investigated as a potential tool to control this widespread weed in the agricultural system of Tabuk region and many areas around the world. 5 T. terrerestris spiny seedcontaining fruits were germinated in 998, 995, 990 and 985 g soil mixed with 2 .00, 5.00, 10.0 and 15.00 g mesquite leaf powder respectively with three replicates in addition to control. The experimental units were set outdoors under tree shade. Irrigation in the morning continued for 15 days, then analysis of variance was carried out to test significance of difference in number of germinated seeds, the germination percentage and germination speed were calculated; coefficient of variation in seedling length and seedling fresh weight was maintained between different treatments. Results showed that number of germinated seeds differed significantly between treatments; both germination % and speed decreased with increased quantity of mesquite leaf powder in the soil; seedling length and seedling fresh weight also differed significantly among the treatments. It has been concluded that P. juliflora leaf powder is effective if introduced to the conventional weed control methods to the control of T. terrestris in particular.

How to cite this article: Elbalola AA. Evidence for increased competitive ability (EICA) in Prosopis juliflora (Sw.) Dc (mesquite) under P. juliflora-Portulaca oleracea L. (purslane) field competition.