Comparative Antibacterial and Antifungal Efficacy of Selected Tanzania Medicinal Plants

Aims: To evaluate the antimicrobial activity of Crassocephalum vitellinum (Benth), Euphorbia hirta (L), Cupressus lusitanica (Mill), Euphorbia inaquilatera (Sond), Ajuga remota (Benth) and Lantana camara (linn) extracts against six Gram negative bacterial strains and two fungal strains.

Study Design: In vitro antibacterial and antifungal assay was done using micro dilution method.

Place and Duration of Study: This study was conducted at Nelson Mandela African Institution of Science and Technology, Arusha-Tanzania, between December 2014 and June 2015.

Methodology: Plant materials were grinded and soaked in solvents which later removed by using vacuum rotary evaporator to obtain crude extracts. Escherichia coli ATCC 11775, Klebsiella pneumoniae ATCC 13883, Pseudomonas aeruginosa ATCC 27853, Salmonella typhi ATCC 6539, Klebsiella oxytoca, Salmonella kisarawe and two strains of fungi; Cryptococcus neoformans and Candida albicans were tested on the prepared crude extracts. The micro dilution method using 96 wells plates was used to determine minimum inhibition concentration (MIC). After 24 hours of incubation, 20 μL of 0 .02% para–iodo nitrotetrazolium (INT) chloride dye prepared in distilled water was added to each well then incubated for 1 hour and 30 minutes at 37°C.

Results: Thirty seven extracts from 6 plant species investigated exhibited antimicrobial activity against tested fungi (C. neoformans and C. albicans) and Gram negative bacteria (E. coli, K. pneumoniae, P. aeruginosa, S. typhi, K. oxytoca and S. kisarawe). C. vitellinum leaf methanolic extract, E. inaequilatera methanolic extract, A. remota leaf and stem methanolic extracts exhibited the highest antibacterial activity against K. oxytoca, P. aeruginosa, S. typhi and K. pneumoniae e with a MIC value of 0.78 mg/mL. L. camara leaf chloroform, ethyl acetate extracts and A. remota leaf chloroform demonstrated high activity against S. typhi, K. pneumoniae e and C. neoformans with MIC value of 0.78 mg/mL. The highest antibacterial activity against E. coli was exhibited by E. hirta methanolic, E. inaquilatera chloroform and ethyl acetate extracts with MIC value of 1.56 mg/mL.

Conclusion: Results showed that Crassocephalum vitellinuum (leaves and stem), Lantana camara (leaves, whole flowers and petals), Cupressus lusitanica (leaves, seed cover and seeds), Euphorbia hirta and Euphorbia inaquilatera possess antimicrobial activities against Gram negative bacterial strains and fungal strains.