ABSTRACT
The study was carried out to investigate the antibacterial activity of an endophytic fungal isolate, Lasiodiplodiapseudotheobromae IBRL OS-64 residing in leaves of a medicinal herb, Ocimum sanctum Linn. Qualitative screeningof the antimicrobial activity was done using an agar plug assay, and the results showed that the fungal isolate wasable to inhibit all the 13 test bacteria. Three Gram-positive bacteria (methicillin-resistant Staphylococcus aureus[MRSA] ATCC 33591, Staphylococcus aureus, and Streptococcus mutans) were the most susceptible species withthe inhibition zones of ≥21 mm. The other three (Bacillus cereus ATCC 10876, Bacillus subtilis IBRL A3, andStreptococcus agalactiae) showed the inhibition zones of 11–≤20 mm of diameter. As for Gram-negative bacteria,Yersinia enterocolitica was the most susceptible to the fungal isolate with the size of inhibition zone of ≥21 mm,followed by Klebsiella pneumoniae ATCC 13883, Salmonella typhimurium, and Shigella boydii ATCC 9207 withthe inhibition zones of 11–≤20 mm, whereas Escherichia coli IBRL 0157, Proteus mirabilis, and Pseudomonasaeruginosa ATCC 27883 were the least susceptible with the inhibition zones of ≤10 mm. Quantitative screeningusing disc diffusion assay showed that the fungal ethyl acetate extract prepared from the fermentative broth(extracellular) exhibited better antibacterial activity compared to the methanolic extract prepared from the fungalbiomass (intracellular). The results showed that the ethyl acetate extract exhibited antibacterial activity against all the13 test bacteria with the inhibition zone sizes of 20.0 ± 0.3–31.3 ± 1.2 mm in diameter for Gram-positive bacteria and10.31 ± 0.6–20.1 ± 0.6 mm in diameter for Gram-negative bacteria. On the other hand, the methanolic extract onlyinhibited three Gram-positive bacteria (MRSA ATCC 33591, S. aureus, and S. mutans) with the inhibition zones of9.0 ± 0.6–11.0 ± 0.3 mm in diameter, whereas only one Gram-negative (S. typhimurium) with the inhibition zone sizeof 13.3 ± 1.5 mm diameter. The minimal inhibitory concentration (MIC) and minimum bactericidal concentration(MBC) values of the ethyl acetate extract on Gram-positive bacteria were in the range of 62.50–125.00 and 62.50–500.00 µg/mL, respectively, whereas for the Gram-negative bacteria, the MIC and MBC values were 125.00–250.00and 250.0–1000.00 µg/mL, respectively. On the other hand, the MIC and MBC values for methanolic extract againstGram-positive bacteria were 250.00–500.00 µg/mL and against Gram-negative bacteria were 1000.00 µg/mL,respectively. Both of the extracts exhibited bactericidal effects on test bacteria with the MBC/MIC ratio ≤4. Further,detail of the effects of the ethyl acetate extract on the bacterial cells was observed from the scanning electronmicroscopy photomicrographs which revealed the severity of the morphological deterioration experienced by theextract-treated cells were beyond repair, and the most possible mode of actions were by interrupting the cell wallbiosynthesis and cell membrane permeability
ABSTRACT
Background: With the increased trend of urbanization of our society, the incidence of various stress related diseases are increasing day by day. People under chronic stress often tends to seek relief through drugs, which may have side effects. But some natural supplements called adaptogen, can be more beneficial in reducing symptoms of stress. Objective: The present animal model experimental study was designed to observe the effects of restraint stress on body weight, serum ALT, AST, Glucose, Cholesterol and their modifications by Ocimum sanctum Linn (tulsi) pretreatment which is an Ayurvedic adaptogen and has a long history of therapeutic use. Study design: For this purpose, 30 albino rats aged 90 to 120 days were included in this study. Twenty rats of experimental group were further subdivided into two groups. One group consisted of 10 rats exposed to one hour restraint stress daily for 7 days and 10 rats of the second group were pretreated with tulsi for 7 days before exposure to stress in the same way. 10 non stressed , non pretreated rats were taken into control group.This study was undertaken in the laboratory of the Department of Physiology,BSMMU during the period from July 2003 to June 2004. Methods: The body weight of all control rats were recorded daily in the morning. Body weight of the experimental rats were recorded just before exposure to stress. After completing the experiment , the animals were sacrificed and blood was collected . Serum glucose, cholesterol and ALT,ASTwere determined by standard laboratory technique. Data were compared among the groups and the results were statistically analyzed using unpaired student t’ test. Results : The body weight in untreated stressed group was significantly lower (p<0.001) than those of the control group and tulsi pretreated group. Serum levels of glucose, cholesterol, aminotrasferases (ALT and AST) were significantly higher (p<0.001) in stressed group than those of control . Again in Tulsi treated group all these biochemical parameters were significantly lower (p<0.001) than those of stressed group. This restraint stress-induced changes in body weight and biochemical parameters may be due to hypophagia, altered secretion of various metabolic hormones and neurotransmitters, changes in membrane permeability & hypovolaemia resulting from stress induced secretion of corticosterone and epinephrine through hypothalamo-pituitary adrenal axis activation. Conclusion: Prevention of stress induced changes in biochemical parameter by tulsi pre treatment indicates its anti stressor effect.