Interaction Between some Phenolic Compounds in Ammi majus Herb (Khillah) Extracts and Antibiotics Against some Selected Bacterial Isolates In vitro

In this study, the in vitro activities of eight phenolic compounds (xanthotoxin, imperatorin, quercetin, hydroquinone, catechol, resorcinol, salicylic acid and vanillic acid) in the petroleum ether and ethanolic extracts of Ammi majus (Khillah) herb and five antibiotics (penicillin, ampicillin, cefotaxime, cephalothin and trimethoprim) against two Gram positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) and three Gram negative bacteria (Escherichia coli, Proteus mirabilis and Proteus vulgaris) alone and in combination are evaluated. Among the seven Ammi majus extracts, the extract (No.7) which contain salicylic acid, resorcinol and quercetin in high concentration showed stronger inhibitory activity against all the bacterial isolates studied with inhibition zones in the range of (16-23) mm. Staphylococcus aureus and Staphylococcus epidermidis were reported to show sensitivity to trimethoprim, ampicillin, penicillin and cephalothin respectively with inhibition zones in the range of (10.5-23) mm and resistance to cefotaxime. While Escherichia coli, Proteus mirabilis and Proteus vulgaris are more resistant to all the antibiotics used. The best synergistic interactions showed trimethoprim and ampicillin with all Ammi majus extracts against Staphylococcus aureus and with all extracts (except with extract No.7) against Staphylococcus epidermidis, and (ampicillin, trimethoprim, cephalothin), (cephalothin, ampicillin), (cephalothin only) with some Ammi majus extracts against Proteus vulgaris, Escherichia coli and Proteus mirabilis respectively. Hydroquinone enhance the activity of ampicillin against Escherichia coli, while vanillic acid inhibit the activity of cephalothin against Escherichia coli and Proteus mirabilis. Staphylococcus aureus followed by Staphylococcus epidermidis and Proteus vulgaris were the most sensitive microbes to most of the combinations.