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Title: Studies on Antimicrobial Activities of Plant Secondary Metabolites of Mikania cordata, Lawsonia inermis and Micromelum minutum

Author: Sharmin Afroza Sultana

Supervisor: Dr. Md. Nural Anwar

Co-Supervisor: Dr. Mrs. Jaripa Begum

Research Field: Medical Microbiology

Batch: 1st

Session: 1999- 2000


Abstract

In the present investigation two plant species such as Mikania cordata & Lawsonia inermis under two families such as Compositae & Lythraceae respectively were screened for their antibacterial activity against eleven human pathogenic bacteria [e.g. Bacillus subtilis BTCC 17, B. megaterium BTCC 18, B. cereus BTCC 19, Staphylococcus aureus ATCC 6538, Salmonella typhi AE 14612, S. paratyphi AE 14613, Shigella dysenteriae AE 14396, S. sonnei CRL (ICDDR.B), Escherichia coli ATCC 25922, Vibrio cholerae AE 14748, Pseudomonas aeruginosa CRL( ICDDR.B)] and two plant species such as Acorus calamus and Micromelum minutum under two families such as Araceae and Rutaceae respectively were screened for their antifungal activity against six phytopathogenic fungi [Alternaria alternata (Fr.) Kedissler, Botryodiplodia theobromae Pat., Colletotrichum corchori Ikata (Yoshida), Curvularia lunata Wakker Boedijn , Fusarium equiseti (Corda) Sacc, Macrophomina phaseolina (Maubl) Ashby]. During preliminary screening, among the four plants, the chloroform soluble fraction of Mikania cordata and Lawsonia inermis were found active against most of the fungal test organisms whereas the petroleum ether fraction of Acorus calamus and the carbon tetra chloride fraction of Micromelum minutum were found active against most of the fungal test organisms. The chloroform soluble fraction of Mikania cordata and Lawsonia inermis, the petroleum ether soluble fraction of the Acorus calamus and the carbon tetra chloride soluble fraction of Micromelum minutum were further fractionated by Vacuum Liquid Chromatography (VLC). The VLC fraction of Mikania cordata and Lawsonia inermis were screened for antibacterial activity and the VLC fraction of Acorus calamus and Micromelum minutum were screened for antifungal activity.
Potato dextrose Agar and Nutrient Agar were used to culture the test fungi and bacteria, respectively. The in vitro antifungal activities were done by the poisoned food technique (Grover & Moore, 1962) and the in vitro antibacterial activities were done by dise diffusion method (Bauer et al. 1966).
In case of Mikania cordata, the fractions showed remarkable activity at the concentration of 1000 µg/disc against the test bacteria compared to the concentration of 500µg/disk. The fraction E & D were found to be more effective than other fractions. The most susceptible organisms to the VLC fractions of Mikania cordata were Bacillus cereus, B. subtilis, Vibrio cholerae, Salmonella typhi, S. paratyphi, Shigella dysenteriae, S. sonnei and Pseudomonas aeruginosa.
In case of Lawsonia inermis, the activity of the fraction C & D were found to be significant. The most susceptible organisms to the fraction C were Bacillus cereus, B. subtilis, Vibrio cholerae, Salmonella typhi, Shigella dysenteriae, S. sonnei and Staphylococcus aureus and to the fraction D were Escherichia coli, Vibrio cholerae, Pseudomonas aeruginosa and Staphylococcus aureus. The VLC fraction C of Lawsonia inermis was subjected to GC/MS analysis and 14 compounds were recorded from the faction C.
The VLC fractions of Acorus calamus were screened for antifungal activity and it was found that the fractions B, C and D showed strong inhibition against the test fungi. The fraction B & C showed 100% growth inhibition against Macrophomina phaseolina, Botryodiplodia theobromae, Alternaria alternata and Curvularia lunata. The VLC fractions B & C were subjected to GC/MS analysis and it were found that the compound Arazon was present in highest quantities in both the fractions B (80.56%) and C (93.47%).
The VLC fractions of Micromelum minutum also showed a marked inhibition against the six fungi tested. Among the fractions, the inhibition produced by the fraction D was found remarkable. It produced 62 to 88% inhibition against the pathogens at the dose of 500µg/ml. The GC/MS analysis was not tried in case of M. minutum due to time limitation.