Plants and plant by-products are now gaining attractiveness in treatment of bacterial infections and food preservation. The objective of this study was to assess antibacterial activity of some Egyptian plant and plant by-products against the locally pathogenic isolates from patients having infectious diseases in our country. Screening of antibacterial activity of ethanol, methanol and hexane extracts of some plants: grape leaves (Vitis vinifera), mulberry leaves (Morus alba), mallow leaves (Corchorus olitorius) and lemon leaves (Citrus limon) toward Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella sp., were investigated. Antibacterial activity was performed by the agar disc diffusion method. The ethanol and methanol extract of tested plant leaves showed promising antibacterial activities against both Gram-positive and Gram-negative tested bacterial isolates due to its great ability to extract those polyphenolic and biological active compounds from natural sources which effectively act against broad spectrum bacteria. Ethanol followed by methanol were found to be the best solvents of choice to extract natural products to get maximum health and medicinal benefits. The results revealed that the extraction efficiency increase with polarity increasing of the solvents, hence the highest extraction done with ethanol and methanol and the lowest extraction with nonpolar solvent n-hexanedid not exhibit any activity against all the tested bacteria. Irradiation at 5 and 10 kGy did not significantly affect the antibacterial activity of all tested plant leaves. Results indicate the potential of these plants for further work on isolation and characterization of the active compounds responsible for antibacterial activity and its exploitation as therapeutic agents

Abstract Dried rosemary leaves (Rosmarinus officinalis Lamiaceae), and dried clove buds (Syzygium aromaticum) were irradiated with γ-irradiation by Cobalt-60 as an irradiation source at different doses (0, 5, 10, 15, 20, 25 and 30kGy) as an effective method for sterilization, pasteurization and food decontamination, considered as safe method , and stored for 12months at room temperature (22±3 0C). The evaluation of irradiation depended on the chemical studies and antioxidant activity of extracted essential oils. Results showed significant difference for the essential oils yield (content %) at different doses during storage time. Compounds were fractionated and identified by GC/MS for extracted essential oils from each of non – irradiated and irradiated dried rosemary leaves and dried clove buds samples, the main components of essential oil extracted from either non-irradiated or irradiated rosemary leaves were 1,8 cineole, camphor and γ-pinene 26.36, 12.63 and 16.98%, respectively, while, eugenol was the major component in clove essential oil (which extracted from non-irradiated and irradiated samples (81.69%). No differences were noticed in the % of essential oils constituents. Antioxidant activity as % of DPPH scavenging increased with the increasing of essential oils concentrations (250 up to 2500ppm). Furthermore, the effect of adding these extracted oils from non-irradiated and irradiated samples as well as their mixture (1:1) on the threshold odor scores of sunflower oil (Mean of acceptable odor levels) was observed. Rancimat test shown the high oxidative stability in sunflower oil supplemented with 0.3% clove essential oil which extracted from 15kGy irradiated sample was 11.99 hrs, its relative stability was 144.11% comparing with the oxidative stability of sunflower oil supplemented with 0.5% rosemary essential oil extracted from non-irradiated sample (9.76hrs) with 117.3% relative stability. Adding different concentrations of rosemary, clove buds essential oils which extracted from different irradiation doses samples and their mixture (1:1) caused slightly increasing in oxidative stability of sunflower oil.