| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作研究所 === 94 === This study was to analyze the extracts from different parts of Australian tea tree (Melaleuca alternifolia Cheel) and their bioactivities. Extracts of leaf were collected for analyzing their chemical constituents. Their antimicrobial activities, cytotoxicity, mutagenesity, antimutagenic, anti-inflammatory and antioxidant activities were also examined. For the non valotile compounds, extractions were carried out by supercritical fluid extraction and liquid-liquid partition using distilled water, etanol, methanol, acetone, ethyl acetate and n-hexane. The water soluable fraction showed the highest yields of 36.32% (w/v) of the total extracts. Steam distalliation was applied to extract the volatile compounds (essential oil) from tea tree leaves. Results of the antimicrobial tests revealed that the tea tree oil had much stronger and more extensive antibacterial activities on 11 microbial species than other non volatile fractions. The tea tree oil at the concentration of 4% showed strong inhibitory effects of 98.7% and 100% against Penicillium italicum and Aspergillus nige, respectively. The effects of pH, metal ions and chemical additives on antibacterial activities of tea tree oil were also tested. Results of the study showed that the antibacterial activities were not affected under different pH values. Adding metal ions and chemical additives in the tea tree oil, however, resulted in a change of its antibacterial activities. The antibacterial activities of tea tree oil were not different regardless whether or not it was subjected to heat treatment at 121°C. The minimum concentration of tea tree oil for inhibiting the growth of bacteria ranged between 0.15% and 3.9% (w/v). In the Ames test with Salmonella typhimurium TA98 and TA100, the results showed that the safety concentration ranged between 0.5 and 5.0 mg/plate as there was no toxicity or mutation detected. In the anti-inflammatory test, the results revealed that both tea tree oil and its distilled water extracts at 50-300μg/ml clearly demonstrated anti-inflammatory activities. The free radical scavenging test, α,α-diphenyl-βpicrylhydrazyl (DPPH), also showed that fresh leaves had more than 91% scavenging effect. On the other hand, the trolox equivalent antioxidant capacity (TEAC) assay indicated that dried leaves had the highest antioxidant capacity, and then followed by fresh leaves. In the analysis of antioxidant compounds, dried leaves contained the lowest concentration of total phenolics (102.1mg/100g). After gel filtration by Sephadex G10, G15, and G25, the anti-bacterial activities of subfractions of water extracts and tea tree oil were lower than their respective original concentrates. Using GC/MS to analyize the molecular weights and identify the chemical structures of tea tree oil, the results showed that the essential oil consisted of 20 different compounds. The overall results suggested that water soluable extract and essential oil from tea tree leaves had excellent antioxidant and anti-microbial activities. Thus, they could be used as new sources of natural antioxidants and food preservatives. In addition, their purified compounds could also be worthy of further study on their pharmaceutical activities.
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