Antimicrobial activity of Mucuna pruriens on selected bacteria

The investigation is aimed to carry out the antimicrobial activities of the methanol extract of Mucuna pruriens leaves. The antimicrobial activity of the extract was determined by the agar well diffusion method against various gram positive, gram negative and spore forming microorganisms and fungi. The methanol extract of M. pruriens showed broad-spectrum antimicrobial activity against all the tested microorganisms except Candida albicans. The results obtained in the study shows that M. pruriens extract can be a potential source of natural antimicrobial agent.


INTRODUCTION
Plant based antimicrobials represent a vast untapped source for medicines and further exploration of plant antimicrobials needs to occur.Antimicrobials of plant origin have enormous therapeutic potential.They are effective in the treatment of infectious diseases while simultaneously mitigating many of the side effects that are often associated with synthetic antimicrobials (Iwu et al., 1999).

Much work has not been done on the leaf, hence the main reason of this investigation.
M. pruriens itch-producing property is attributed to the trichomes (hair) present on the pods.It has been established that this unique property is accounted by the presence of 5-hydroxy tryptamine (5-HT) in the hair (Armstrong et al., 1953).Some reports show that antihistaminics afford protection against the itch (Broadbent, 1953).In this work, we tested the antimicrobial activity (against gram positive, gram negative and spore forming bacteria and also fungi) of the methanol extract of the leaf of M. pruriens

MATERIALS AND METHOD
The leaf of M. pruriens was collected from bushes around the Obafemi Awolowo University Ile-Ife Osun State, Nigeria.The leaf was identified in the herbarium of the Faculty of Pharmacy of the Obafemi Awolowo University Ile-Ife Osun State, Nigeria.The leaf was extracted using methanol.Antimicrobial activity was determined by agar-well diffusion method (Kavanagh, 1963) and minimum inhibitory concentrations were determined (Russell and Furr, 1977). .Their activity at 240 mg/ml is comparable to that of the control used (streptomycin at a concentration of mg/ml).Candida albicans was not sensitive to the extract.On the basis of the result obtained in this present investigation, we conclude that the methanol extract of M. pruriens leaves had significant in vitro antimicrobial activity.The obtained results may provide a support to some uses of the plant in traditional medicine.Further studies are recommended to isolate the active components responsible for the antimicrobial activity.

Microorganisms
Bacillus subtilis NCTC 8263, Pseudomonas aeruginosa ATCC 10145) were obtained from the stock culture of Department of Pharmaceutics, Obafemi Awolowo University Ile-Ife Osun State, Nigeria.

Table 1 .
Antimicrobial activity of Mucuna pruriens leaf extract

Zones of inhibition (mm) 3 Mucuna pruriens (mg/ml)
Table 1 above indicates that the extract inhibited the growth of all the tested microorganisms with the exception of Candida albicans to various degrees.The extract showed strong antibacterial activity against S. aureus NCTC 6571, E. coli NCTC 10418, B. subtilis NCTC 8263, Proteus mirabilis NCIB 67, P. aeruginosa ATCC 10145 (which is most times resistant to most antimicrobial agents)