ANTIBACTERIAL ACTIVITY LEAF EXTRACTS OF STRYCHNOS NUX VOMICA L. - A MEMBER OF LOGANIACEAE

The present study investigates the antibacterial activity of various solvents leaf extracts of Strychnos nux vomica against four different bactria strains like Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella paratyphi b, Alternaria alternate, Aspergillus flavus, Penicillium notatum and Cladosporium carrionii. All the results were compared with respective positive control.


INTRODUCTION
Medicinal plants are rich in traditional knowledge drastically recede in the wake of burgeoning population pressure, acculturation, rapid modernization, multi various human developmental activities. A lot of current research work in ethnobotany is concerned with the loss of traditional knowledge and the preservation of biological diversity in remote parts of the world where cultures and their ecosystems are being destroyed by development (Sereiti et al., 1999). The ethnobotanical investigations may become invaluable to rescue knowledge in imminent danger of being lost and to find out new bioactive compounds in plant. The use of plant preparations as foodstuff, insecticides, CNS active, cardio active, antitumor and antimicrobial agents are some examples of immense chemical diversity in plants (Balick et al.,2000).
The phytochemical techniques various active principles of many medicinal plants have been isolated and introduced as valuable drugs in morden system of medicine (Dennis,1988). Strychnos nux vomica is an evergreen tree native to South East Asia and India belonging to the family Loganiaceae. It is medium sized tree found mostly in open habitats. Two poisonous alkaloids, Strychnine and brucine are found in Strychnos nux vomica tree. Traditionally used for treating acute diarrhoea, mixed with lemon juice and made into pills and taken orally during dysentery, arthritis, rheumatism and piles (Dubey et al.,2012).

Plant collection and identification
The plant Strychnos nux vomica was collected from the Nilgiris, Tamilnadu, India. The plant was identified and authenticated by a plant taxonomist.

Extraction of the plant material
About 250 g of freshly collected sample of Strychnos nux vomica (leaf) was separately washed 2-3 times with water followed by distilled water and shade dried. All the dried parts were pulverized by mechanical grinder (willey mill) to get the powder through 100 mess sieve and then stored in a refrigerator. It was extracted by cold extraction method with petroleum ether, ethanol, methanol and aqueous. Then all the extracts were concentrated in a rotary evaporator to yield a syrupy residue and used for all the phytochemical analysis.

Disc diffusion method
The antibacterial activity of leaves extracts of Strychnos nux vomica was evaluated by disc diffusion method. The culture media were prepared and autoclaved at 121 o C at 15 psi for 20 minutes and stored in refrigerator. The media were melted before the process of inoculation. The clean dry sterile Petri dishes were poured with nutrient agar medium for bacterial strains. Ten number of 10 ml broths were prepared separately for nutrient agar medium in test tubes and plugged with cotton and autoclaved. The test tubes were labeled according to the microbes to be inoculated. The bacterial strains were inoculated into the nutrient broth aseptic conditions and incubated at 37+0.5 o C for 18 hours. After incubation, the bacteria were smeared on the nutrient agar plate respectively using a sterile cotton swab. A sterile disc of 6 mm diameter was loaded with known quantity of 10 mg of dried crude extracts of aqueous, petroleum ether, ethanol and methanol extracts and dissolved in10 ml of DMSO. These discs were placed on the surface of the media. The positive control antibiotics viz., chloramphenical (10μg) were maintained. Then the Petri dishes were incubated at 37+0.5 o C for 12 to 14 hours. The diameters of inhibition zones were measured. (Bauer et al.,1966).

RESULTS
Aqueous, petroleum ether, ethanol and methanol leaves extracts of S. nux vomica was assessed for antibacterial (Table 1). The results showed that among the four extracts, methanol showed significant result of antibacterial activity. When compared with other extracts, aqueous extract showed minimum level of inhibition. Among the seven bacterial strains, maximum zones were observed in the following bacterial strains such as B. subtilis, P. aeruginosa and E. coli. S. paratyphi-b were found to be highly susceptible to methanol extract. The inhibition zone of methanol extract was similar to that of the control, chloramphenical. Table 1. Antibacterial activity of various solvent leaves extracts of Strychnos nux vomica.

S.
Microorganisms No.

DISCUSSION
The results showed that the aqueous, petroleum ether, ethanol and methanol leaves extracts of S. nux vomica has revealed a significant results of antibacterial activity when compared with other extracts except aqueous showed minimum level of inhibition. Among all the bacterial strains, maximum zones were observed in the following bacterial strains such as B.subtilis, P. aeruginosa and E. coli. S. paratyphi-b were found to be highly susceptible to methanol extract. Plant extracts are potential sources of novel anti-microbial compounds especially against bacterial pathogens. Phytomedicine can be used for the treatment of diseases as in case of Unani and Ayurvedic system of medicine or it could be the base for the development of medicine, a natural blue print for the development of a drug (Didry et al., 1988). The plant extracts were screened against human pathogenic bacteria to check antibacterial activities by agar well diffusion method, which showed valuable zone of inhibition. Specifics zone of inhibition against different types of pathogenic bacteria (Alam Morshed et al., 2011). Our study contradicted the earlier reports of Gnanavel et al (2012).

CONCLUSION
In the present study indicated a significant antibacterial activity effect of the leaf extracts of Strychnos nux vomica and exposes the existing potential of the other parts of the tree to be explored for other medicinal benefits of the human kind.