Biological Activity of Some Irradiated Plant Extracts on Some Pathogenic Bacteria

The present investigation was conducted to evaluate the antibacterial activity of 10 plant and plant by-products: grape (Vitis vinifera), mulberry (Morus alba), mallow (Corchorus olitorius), lemon (Citrus limon), purslane (Portulaca olerace), rosemary (Rosmarinus officinalis L), ficus (Ficus retusa L), black myrobalan (Terminalia chebula), cinnamon (Cinnamomum veru) and ginger (Zingiber officinale) against 45 locally pathogenic bacterial isolated from patients having infectious diseases in some Egyptian hospitals using the agar disc diffusion method. These isolates were identified as Staphylococcus aureus (St1-16), Escherichia coli ( Ec1-10), Pseudomonas aeruginosa (Ps1-15) and Salmonella spp. (Sa1-4). Among 10 ethanolic plant extracts, 4 extracts from leaves of grape, mulberry, mallow and lemon were found to exhibit high potential antimicrobial properties against 45 bacterial isolates. These plants were extracted by different solvents (ethanol, methanol and n-hexane) then irradiated with gamma-radiation doses (5 and 10 kGy) and compared with non-irradiated plants, and result showed that ethanol or methanol extracts were more active than irradiated extracts. Hexane extracts from irradiated or non-irradiated plants had no effect on the pathogenic tested bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of grape, mulberry, lemon and mallow were determined at concentrations of 2.56 mg/ml to 0.01mg/ml. Four tested ethanolic plant extracts were the most active with MIC ranged from 0.08 to 0.16 mg/ml against Ps. aeruginosa (Ps9), 0.32 mg/ml against S. aureus (St3), E. coli (Ec3) and Salmonella sp. (Sa1).whereas, the MBC value ranged from 0.32 to 1.28 mg/ml of tested extracts. The mode of action of ethanol extracts from leaves of tested plants was studied and results indicated that, ethanol grape extract had a bactericidal effect with ratio 2 against S. aureus (St3), E. coli (Ec3) and Ps. aeruginosa (Ps9) while grape extract had a bacteriostatic effect against Salmonella sp. (Sa1). Tested extracts of mulberry, mallow and lemon had a bactericidal effect for S. aureus (St3) and E. coli (Ec3) isolates with ratio of 2 and bacteriostatic effect against Ps. aeruginosa (Ps9) and Salmonella sp. (Sa1) with ratio . 4. Results also indicated that, the ability of 4 tested pathogenic bacteria for strongly biofilm formation with densities ranged from 0.67-0.80. Anti-biofilm activity of 4 tested plant extracts were evaluated by tested isolates at suitable SIC values. Results indicated that, all ethanol extracts inhibited biofilm formation with percentage ranged from 41.0 to 66.0 % at SIC ranged from 0.04 to 0.16 mg/ml. The highest percentage of anti biofilm activity against S. aureus St3 was observed with lemon extract at 0.16 mg/ml followed by mulberry and grape extracts (55 and 50%), respectively. The lowest anti biofilm activity was 47% with mallow extract. As grape, mulberry and lemon leaves ethanolic extracts have excellent cytotoxic activity against colon cancer cell lines (HCT-16) and potential anti-tumor activity. On the other hand, mallow leaves extract showed no anti-tumor activity (negative effect). Five phenolic compounds appeared in ehanolic leaf extracts of grape and mulberry using HPLC during 9.53 min of retention time. The phenolic compounds of both extracts being gallic acid (1.28, 1.82 μg/ml), coumaric acid (2.38, 4.64 μg/ml), ferulic acid (1.19, 6.56 μg/ml), chlorogenic (3.56, 2.67 μg/ml) and caffeic acid (2.6, 3.96 μg/ml)