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Antifungal Activities And Chemical Characterization Of Neem Leaf Extracts On The Growth Of Some Selected Fungal Species In Vitro Culture Medium. *Mondall , N. K.; Mojumdar., A.; Chatterje, S. K.; **Banerjee, A.; Datta, J.K.; Gupta, S. *Institute of Science Education and ** Environmental Science Department, The University of Burdwan, Burdwan, West Bengal, India nabakumar_mondal@indiatimes.com Code Number: ja09008 ABSTRACT The efficacy of different extracts of neem leaf on seed borne fungi Aspergillus, Rhizopus and chemical characterization of the neem leaf extracts were studied in vitro on the culture medium. The growth of both the fungal species was inhibited significantly (p<0.01) and controlled with both alcoholic and water extract of all ages and of the concentrations used. The alcoholic extracts of neem leaf was most effective in comparison to aqueous extract for retarding the growth of Rhizopus and Aspergillus. The crude aqueous and alcoholic leaf extracts of neem was more effective in inhibitions of growth of the fungi Aspergillus in comparison to inhibitory effects on Rhizopus growth in the artificial culture medium. Leaf extracts of neem which are cheap and environmentally safe are promising for protecting crop species against the fungal infestation and leading towards improvement of the crop in terms of yield and productivity. @ JASEM A large number of chemicals have been developed for the control of plant diseases. But due to overgrowing awareness of the hazardous side effects of these chemicals, more and more emphasis is being given to the use of biocontrol agents. Now major challenge is felt in the field of plant pathology to introduce some ecofriendly and safe alternative control strategies for agriculture, which led researchers to turn their attention to plants and microorganisms as sources of biocontrol agents. As the sources of biocontrol agent, neem has already emerged at the top of the list of plants with the highest potential. The following species of neem trees of Meliaceae family have been the subject of botanical biocontrol research: Azadirachta indica A. Juss., A. excelsa Jack, A. siamens Valeton, Melia azadirachta L, M. toosendon Sicb. and Zucc. and M. volkensii Gurke. The Meliaceae specially A. indica (Indian neem tree), contains at least 35 biologically active principals of which Nimbin and azadirachtin (T.D. Pennigton el al., 1981) are the most active insecticidal ingradients and are present predominantly in the seeds, leaves and other parts of the neem tree (Mulla et at., 1999). In this study the effect of the leaf extracts of various ages of neem leaves along with different extractants. On in vitro culture medium of Aspergillus and Rhizopus were studied and subsequent chemical characterization of the need leaf extracts were mediated for its antifungal activity. MATERIAL AND METHODS Extraction of leaf extracts: Juvenile and mature leaves were collected separately from Azadirachta indica plants growing in University campus, Burdwan University. For antifungal and secondary metaibolite studies fresh leaves of 2-4 days old and 7- 9 days old were collected during emergence time (February-March.). Collected fresh leaves of A. indica (Neem) were washed thoroughly in tap water and sterile distilled water, air-dried at 27°C, weighted (l00g) and ground in a sterile mortar. The paste was added to 100ml of sterile distilled water in 250 ml beaker, stirred vigorously and allow to stand for 1 hour and then filtered through four folds of sterile cheese cloth to obtain water extract. Percentage inhibition of fungi growth by the leaf extracts was calculated using the formula: % FG = Dc-Dr/Dc x100 Where: %FG = % inhibition of fungi growth Dc = diameter of control In vitro tests: Species of Aspergillus and Rhizopus were collected from the Mycology and Plant Pathology Laboratory, Department of Botany, The University of Burdwan and are maintained in pure live on potato dextrose agar (PDA) slants at 4 0C. For evaluation of in vitro antifungal activity of the biocide (plant extract of Azadirachta indica) the phytoextracts were added to Potato Dextrose Agar (PDA) medium in different concentrations (0.1%; 0.5% and 1%) in separate sterilized petriplates. Each plate was inoculated with a mycelial disc (5mm diameter) taken from 7-day-old culture raised on PDA. The inoculated plates were incubated at 30± 1°C and the diameter of colony of the pathogen was measured in each case for successive 7 days (Dutta, 2001). The results are shown in table 1. Chemical characterization of Neem Isolates: For extraction, isolation and identification of active ingredients such as alkaloids, phenolics, terpenoides etc. solvent extraction procedure of Harborn, 1998 was adopted. Extracts obtained as above Harborn, 1998, were concentrated to 1ml and 20μl loaded on TLC plates (Silica gel G 0.2 ml) and developed by the following solvents: Acetic acid: Ethanol (1:3); Acetic acid: Water (1:10); Ethyl acetate: Ethanol (1:3); Hexane: Ethyl acetate (1:1); Methanoi: Toluene (8:2). The spot was observed on the TLC plates and Rf value was calculated by using the following formula : Rf = distance traveled by center of component / distance traveled by solvent front Rf value signifies the retention factor i.e., more the molecular weight the more will be the distance traveled by the isolates. All chemicals were Anal R grade. Standard compound Nimbin was obtained from Himalaya Drug Chemicals as "Neem" (Ref: BPN 329). RESULTS In vitro tests: Results of the present investigation shows that the growth of both the saprophytic fungus Rhizopua and Aspergillus was inhibited with the crude aqueous and alcoholic extract of different aged leaves of Azadirachla indica (Table-1). From the result it is evident that the inhibition of growth of both the fungus was more pronounced with ethanolic leaf extracts as compared to aqueous leaf extracts. Significant inhibition of growth of Rhizopus and Aspergillus observed in the artificial culture media containing older leaf extracts of Azadirachta indica. Of the concentration of aqueous and alcoholic leaf extracts of different aged leaves it was observed that higher concentrations leaf extracts were more effective on growth inhibition of both Rhizopus and Aspergillus and it was also noted that from early period of incubation inhibition of growth occurred (Fig.-l & 2, Plate: 1). Chemical characterization of Neem leaf isolates: Semi quantitative estimation and identification of active principles of the crude leaf extracts of Azadirachta indica were performed by TLC method (Table: 2, Plate: 2). In the present study TLC separation of ethanolic extract of the plant material present a large number of compounds as revealed by fluorescents spots when visualized under UV light (Table: 2). Two of the spots (0.09 and 0.91) were found to have similar Rf values as that of the standard Nimbin. Other spots could not be identified due to lack of standards. Among the various TLC solvent tries such as Acetic acid: Ethanol (1:3); Acetic acid: Water (1:10); Ethyl acetate: Ethanol (1:3); Hexane: Ethyl acetate (1:1); Methanol: Toluene (8:2). Hexane: Ethyl acetate (1:1) was the best as it was able to separate 9 spots from the crude extract and Methanol: Toluene (8:2) solvent exhibits the second best as it was able to separate 7 spots from the crude extract. DISCUSSION The efficacy of different extracts of neem against the growth of Aspergillus and Rhizopus was treated in vitro and chemical characterization of the neem leaf extracts were mediated by TLC method. The present results of this investigation exhibits the radial growth of Aspergillus and Rhizopus was inhibited in vitro By water and ethanolic leaf extracts of Azadirachta indica, suggesting the presence of antifungal substances in the plant tissue, which agreed with the results reported by other workers on different pathogens and plants (Tewari and Nayek, 1991; Al-Abed et a/., 1993, Qasem et al, 1996; Amadioha 1998 and Amadioha 2003). The alcoholic leaf extract was more effective than the water extracts of neem. It was also observed that the mature leaf (7-9 days old) extracts have more inhibitory effect than that of young (2-4 days old) one. The differences in the toxicity of different extracts could be attributed to the presence of the active principles that are extracted by different solvents, which may be influenced by several factors such as age of plant, method of extraction and type of extracting solvent (Nicolls, 1969 and Qasem et al, 1996). The greater effectiveness of ethanolic as compared with water extract of the neem leaf may be due to differences in constituent extraction (Shekhawrat and Prasads, 1991). It has been previously reported that the active ingredients of neem constitute mostly of triterpenoides, eg, Nimbin, Nimbidine, Azadirachtin etc. (Brahmachari, 2004). In the present study TLC separation of ethanolic extract of the plant material present a large number of compounds as revealed by fluorescents spots when visualized under UV light (Table: 2). Two of the spots (0.09 and 0.91) were found to have similar Rf values as that of the standard Nimbin. Other spots could not be identified due to lack of standards. Among the various TLC solvent tries such as Acetic acid: Ethanol (1:3); Acetic acid: Water (1:10); Ethyl acetate: Ethanol (1:3); Hexane: Ethyl acetate (1:1); Methanol: Toluene (8:2). Hexane: Ethyl acetate (1:1) was the best as it was able to separate 9 spots from the crude extract and Methanol: Toluene (8:2) solvent exhibits the second best as it was able to separate 7 spots from the crude extract. Therefore, from the foregoing discussion it may be concluded that Azadirachta indica, a common medicinal plant could be exploited as the source of a potent biocide that have immense fungi toxic effect to several fungal pathogens like Aspergilhts and Rhizopus. Acknowledgement: I am indebted to Prof. N.C. Chatterjee and Dr. Sikha Dutta, of Botany Department, Burdwan University for their continuous encouragement and by providing me laboratory facilities in the Mycology and Plant Pathology Laboratory B.U. for this project work. My debt to Sri Dipjyoti Chskraborty and Jayanta Chakroborty research scholars of Botany Department, B.U. for their sincere help on this project work. REFERENCES
Copyright 2009 - Journal of Applied Sciences & Environmental Management The following images related to this document are available:Photo images[ja09008t2.jpg] [ja09008f1.jpg] [ja09008f2.jpg] [ja09008t1.jpg] |
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