Study On Antimicrobial Activities Of Extracts From 17 Species Of Qing Hai-tibet Plants And Particial Antimicrobial Mechanism On Methanol Extracts From Carex Tristachya

For effective utilization of qinghai-tibet plateau unique plant resources, development of natural food preservative. the antimicrobial activities from 17 species of plants Qing hai-Tibet plants were screened against four fungus Penicillium expansum, Alternaria alternate, Trichothecium roseum, Fusarium semitectum and four bacteria Staphylococcus aureus, Pseudomonas fluorescence, Bacillus subtilis, Escherichia coli in vitro. A primary antimicrobial mechamism was studied on methanol extract of Carex tristachya in biochemical and ultrastucture level.The reaults showed as below:1. Extracts from 17 plants had antimicrobial activity in different degree. Ethylacetate extracts of Carex tristachya showed the best antimicrobial, which inhibition E. coli rate for 71% and MIC value of 0.05g/ml; the control effects of the extracts on fruit rots were determined in harvested muskmelon.Fruits were wounded and artificially inculated with spores(1×106 cfu/ml) of F. semitectum. The results indicated that Fusarium rot of melon fruits could be controlled completely at 0.5g/ml.2. Scanning electron microscope and transmission electron microscope revealed ultrastructural modifications caused by ethylacetate extract of Carex tristachya. Cytodem and cellular organ of F.semitectum and P. fluorescence markedly alteration.3. Enzyme exudation and biochemiscal process were investigated on the addition of ethylacetate extract ofCarex tristachya, the extract enhanced the activity of laccases (Lac) and inhibit superoxide dismutase (SOD).4. Activities of PAL, PPO and POD were tested by inoculation with ethylacetate extract of Carex tristachya (1g/ml) + F. semitectum in melon fruits. The extract failed to stimulate the activity of these defense enzymes.In vitro s experiment shows that the same extracts has different antimicrobial activities for different strains, and against bacteria better than fungi, The results also suggested that ethylacetate extracts of Carex tristachya are able to effect the activity of enzymes of F. semitectum and destroying the mycelia and spores the normal growth.