| Melaleuca bracteata known as the Myrtaceae family Melaleuca genus colored macrophanerophytes ,was cultivated in recent years. It had high ornamental value at natural grown condition with bright green-yellow leaves and special smell. At the same times ,it also had a high environmental tolerance .The object of this experiment was collected from Wuzhishan city Hainan Province, we have had a systematic research on antioxidant activity of the Melaleuca bracteata ethanol extracts as well as the antioxidant and antibacterial activity of Melaleuca bracteata leaf essential oil. This thesis consisted of following three part:1. The method of solvent extraction of Melaleuca bracteata leaves was optimized by using the single factor optimization, central composite rotat design and the response surface method before the antioxidant activity was determined.The total polyphenol content, total flavonoids content, DPPH radical scavenging capacity and ferric-reducing antioxidant power were selected as the optimization goal. The results indicated that ethanol concentration have a significant effect on antioxidant substance content of leaf extract in single factor optimization, followed by extraction time and extraction temperature;Response surface optimization showed that the extracts has the best antioxidant acitivity at extraction time 3.65 d, extraction temperature of 53.26? and 34.81% ethanol concentration, the highest total polyphenol content was 88.6±1.3 mg GAE/g DW, the flavonoids content was 19.4±0.2 mg RE/g DW, ferric-reducing antioxidant power was 2.37±0.01 mM Fe2+/g DW, DPPH radical scavenging capacity was 86.0±0.3%. The results showed that the content of antioxidant active substances of Melaleuca bracteata leaves was rich and could be used for the extraction of natural antioxidant active substances, and had good application development prospect.2. Steam distillation method was used to extract essential oil of Melaleuca bracteata leaves , four kinds of organic solvent petroleum ether, ethyl acetate, chloroform and n-butanol were used to extract, got four phase essential oils, the color of essential oil was light yellow to deep yellow,had a special smell, extraction yield were 0.882±0.026 %,2.645±0.069 %,1.354±0.060 % and 1.233±0.061% respectively. Ethyl acetate had highest efficiency .Essential oils of petroleum ether extraction had highest total polyphenol content and flavonoids content,which were 6.617±0.535 mg GAE/g SW and 7.086±0.452 mg RE/g SW; At the same time, the petroleum ether extraction essential oil had the highest antioxidant activity, IC50 of DPPH and ABTS radical scavenging experiments were 4.180±0.050 mg/mL, 5.400±0.140 mg/mL, high iron reducing power was 8.935±0.067 mg RE/g EO, antioxidant activity was positively correlated with essential oil concentration;Using gas chromatography -mass spectrometry (GC-MS) combination method to analysis the composition of essential oils, 40 compounds were identified,accounting for 99.2% of the total essential oils, mainly contain some phenols, ethers, esters,alcohols, hydrocarbon and amine substance, the highest content of methyl eugenol(65.49%); Followed by Methyl 3,4,5-trimethoxybenzoate (7.92%), Estragole (5.93%),linalool (3.46%), etc.The main antioxidant active substances of the essential oil of Melaleuca bracteata leaves were small polar polyphenols, and the main component content is more single, development research is more convenient.3. Antimicrobial activity of essential oil showed that essential oil had high inhibitory activity against five kinds of plant pathogens,such as Pyricutaria oryzae Cav., Bipolaris cactivora,Alternaria solani, Calletotrichum musae and Fusarium oxysoporum,concentration for 50% of maximal effect(EC50) were 33.78±2.35, 94.32±5.43, 138.25±9.72,85.37±5.01 and 205.76±14.70 ?g/mL respectively. And the results of the determination of enzyme activity showed that essential oil had high inhibitory activity for protein content,SOD enzyme and CAT enzyme of Pathogen. Among them, the inhibition effect of Pyricutaria oryzae Cav was the best, although it had poor activity compared with that of myclobutanil (3.49±.47?g/mL),it had a higher acitivity compared with plant source Matrine (65.42±02.83?g/mL).When concentration of the main ingredient methyl eugenol of essential oil was 200 pg / mL,it had the best inhibitory activity for Calletotrichum musae and inhibition rate was 68.04%,worse 5.06% than the essential oil. Compared with Streptomycin sulfate and gentamycin sulfate, essential oil had a good inhibitor acitive for Escherichia coli, Bacillus subtilis,Pseudomonas aeruginosa and Staphylococcus aureus,the minimum inhibitory concentration were 0.20, 0.40,0.45 and 0.10 mg/mL respectively.It showed that essential oil of Melaleuca bracteata had a good antimicrobial activity for plant pathogenic and foodborne bacteria,and it had potential to develope into botanical pesticides. |
PDF Full Text Request