Physiological Studies on some Medicinal Plants of the Family Lamiaceae Grown Wildly in Saint Catherine Peninsula

: Comparative physiological studies were carried out on five wild medicinal plant species of Lamiaceae , namely (Qartam) Stachys aegyptiaca Pers., (Attan) Lavandula pubescens L., (Rosemary) Rosmarinus officinalis L ., (Sharma) Ballota kaiseri Tackh . and (Marmaria) Salvia multicaulis Vahl. The results showed that, Salvia multicaulis had the highest essential oil content (7.46%) which might be attributed to the increased thickness of midrib, lamina, length and width of both phloem and xylem tissues as well as to the number of xylem arms/bundle in the 3 rd leaf. The highest value of free amino acids and phenolic compounds (8.76 and 12.16 mg/100 g FW, respectively) were found in Stachys aegyptiaca . The maximum stomatal number (650 stoma/mm 2 ) was found in Ballota kaiseri. However, Lavandula pubescens had the maximum length and width of stomatal aperture (22.85 and 2.85 µm, respectively). Analysis of essential oils by GC-MS showed 87 different essential oil constituents in all investigated species. Essential oils showed high efficiency as an antimicrobial agent against some pathogens. Salvia multicaulis had a high potential against Salmonella typhimurium and Staphylococcus aureus with maximum clear zones of microbes (22 and 30mm, respectively). Lavandula pubescens had a positive effect against Escherichia coli with a maximum clear zone of 13 mm, due to the high total antioxidants (72.4%) in leaves. Rosmarinus officinalis showed high impact against Pseudomonas aeruginosa and Candida albicans with maximum clear zone of 25 and 22 mm, respectively. The high efficiency of essential oils against pathogens was correlated with specific bioactive constituents.