Introduction

Essential oils are found in various parts of plant  body such as seeds, flowers, leaves fruits are concentrated in certain special cell and glands because of  their properties.They are widely used in perfumes, flavorings and medicine. Essential oils are common group of natural  product present in aromatic medicinal plants and are the most important source of life saving drugs for the majority of the world population. Medicinal plants represent a rich source of antimicrobial  agents.

Plants are used medicinally in different countries are source of many potent and powerful drugs. The most common hospital infection is caused by opportunistic pathogen Pseudomonas aeruginosa.  Pseudomonas aeruginosa is a notorious  nosocominal pathogen capable of  surviving for extended periods in almost any liquid environment even in some disinfectant solution.

Pseudomonas aeruginosa infect people who are already ill or injured. It’s not highly virulent but is a successful opportunistic pathogen because it has pilli for adherence and an extracellular slime layer that interfers with phagocytosis. Burned  patient are at particularly high risk because they have lost their skin production. Pseudomonas aeruginosa infection are extremely difficult to treat with antibiotics. The efficacy of various species of medicinal plants against a variety of pathogen has found out by a number of workers ^1-10.

Chemotherapy is the main approach in the treatment of bacterial infection. A major problem with various antibiotics include toxicity at high cost and low efficacy. These problems therefore necessitate a constant search for antimicrobials. In the present study essential oils from seven medicinal plants which have been traditionally used as antimicrobial agent were examined for antimicrobial activities against  Pseudomonas aeruginosa.

Material and Method    

 Plant Material

Fresh leaves of Eucalyptus globulus, Mentha arvensis, seeds of Sapindus mukorossi, Myristica fragrans, fruit of Emblica officinalis, fresh flowers of Jasminum sambac, Rosa indica were collected from the different location of Bhopal. Plants samples were washed, shade, dried at room temperature.The dried and ground plant parts were extracted with different solvents (hexane, dichloromethane, methanol, chloroform) by steam distillation.

Extraction of essential oil

Raw plant material consists of leaves, flowers, fruits, seeds is put into distillation apparatus using soxhlet apparatus. Weight of  plant material has been taken before loaded in the soxhlet  apparatus and the water is heated so that the steam passes through the plant material vaporizing the volatile compounds. The vapour flow through a coil where they condense back to liquid which is then collected in the receiving vessel.

Maintenance of microbial culture

In the present study Pseudomonas aeruginosa is taken as the test microrganism. The cultures were maintained on nutrient agar slants and stored at 4⁰C. Stock culture were subculture at regular intervals.

Disc diffusion method

Antibacterial activity of essential oils of seven plant were tested against Pseudomonas aeruginosa .This bacteria grow in nutrient agar medium. Nutrient agar medium  was poured into the plate to obtain uniform depth and  allowed to solidify. The standard inoculums suspension (10⁴CFU/Ml) were streaked over the surface of the media. 4mm diameter discs were prepared with Whatman No.1  filter paper and used for the study 10μl of essential oil was diluted with volume of 5% ethanol and impregated on the filter paper disc and placed on the surface of the plate with sterile forceps and gently pressed to ensure contact with the inoculated agar surface Penicillin (5 μg /disc) was used as positive reference standard to determine the sensitivity of the tested strain. 5% Ethanol was used as negative control. Finally the inoculated plate were incubated at 37⁰C for 24 hrs and the inhibition zone was observed.(Table-1)

Table 1: Zone of inhibitory activity (in millimeter) of different plant extracts against Pseudomonas aeruginosa.

Result and Discussion

The antibacterial activity of seven plant species extracts were assayed in vitro by agar disc diffusion method against Pseudomonas aeruginosa . Table-1 summarizes the Pseudomonas growth inhibition by different extracts of the screened plant species. A significant inhibition zone of Pseudomonas aeruginosa was found in all  solvent extracts of Eucalyptus globulus showing 15,10,4,8mm inhibition. Emblica officinalis and Myristica fragrans presented moderate inhibition in methanol, dichloromethane, hexane, chloroform successfully inhibition against Pseudomonas aeruginosa.The highest antibacterial activity of methanol leave extract of Eucalyptus globulus was 15mm. and least antibacterial activity recorded in methanol flower extract of Jasminum sambac is 1mm.                        

The result of present investigation clearly indicate that Eucalyptus globules is potentially a good source of antimicrobial agent. It can be used as development of new therapeutic agent.

The present study was conducted to investigate the in vitro antimicrobial activity. However, the plants differ significantly in their activity against nearly all the extracts of  Eucalyptus globulus presented significant inhibition against Pseudomonas aeruginosa. The Gram negative strain Pseudomonas aeruginosa is a common bacterium that can cause diseases in animals and humans. Infection associated with Pseudomonas aerugionsa are pneumonia, septicemia, meningitis, brain abcesses, urinary tract infection. The most common hospital infection is caused by opportunistic pathogen of Pseudomonas aeruginosa. Pseudomonas aeruginosa are extremely difficult to treat with antibiotics. In evidence from expt,  plant such as Eucalyptus globulus showed high activity against Pseudomonas aeruginosa.

Many microorganisms which cause damage to human health exhibit drugs resistantce due to inadequate use of  antibiotics. Thus there is a need for the discovery of  new substance from natural source including plants. Plants produce a diverse range of bioactive molecules making them rich source of different types of medicine.The present result show that the methanol leaf extract of Eucalyptus globulus showed more inhibitory effect than the other plant extracts.

 Conclusion

In conclusion the present investigation comes out with the fact that methanol leaf extract of Eucalyptus globulus is potentially a good source of antimicrobial agent. Thus in the study a certain value of plants used in ayurveds which could be of considerable interest to the development of new drugs has been tested for their efficacy against pathogenicity. These promissory extract opens the possibility of finding new clinically effective antibacterial compounds.

Reference  

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