Studies Of Pharmacological Action Of The Essential Oil Of Melaleuca Alternifolia (tea Tree Oil)

Background:The essential oil of Melaleuca alternifolia, commonly known as tea tree oil(TTO), has a long history of use as a topical antiseptic. Numerous studies have addressed the antimicrobial property and the antiinflammatory activity of TTO. In recent times,it has gained a reputation as a safe, natural and effective antiseptic. This has led to a resurgence in popularity and currently it is incorporated as the principal antimicrobial or as a natural preservative in many pharmaceutical and cosmetic products intended for external use. In 1999, some Australian tea trees were replanted in our country. The concentrations of essential components of TTO distilled from homegrown trees are different to those of Australian TTO, which possibly leads to the variation of the antimicrobial and antiinflammatory properties of homegrown TTO. So, it is necessary to study the antimicrobial and antiinflammatory actions of homegrown TTO in order to understand the pharmacological activities of the oil and to provide the significant information for applications of it. PartⅠInvestigation of Antimicrobial activity of TTO Objective: To confirm the antimicrobial action of homegrown TTO against Candida albicans, drug-resistant Staphylococcus aureus, Bacillus subtilis and its spore, Pseudomonas aeruginosa, Escherichia coli and Shigella dysenteriae, and to evaluate the variation of the antimicrobial activity of homegrown TTO. Method: All test microorganisms were incubated overnight in broth media containing different concentrations of TTO, and results of cultures were observed. Then the mixtures from the broth were inoculated into broth and solid media and were cultured overnight, and finally, results of cultures were observed again. The paper disc agar diffusion method was used to determinse inhibition zones of several concentrations of homegrown TTO on all bacteria and Candida albicans. Result: TTO at≥1%(v/v)obviously exerted the antibacterial effect on P.aeruginosa;C.albicans and other bacteria showed significant sensitivity against TTO at≥0.5%(v/v);To 0.25%(v/v)TTO against S.dysenteriae and 0.125%(v/v)TTO against B.subtilis and its spore, its antibacterial action were still clearly observed;The different concentrations of homegrown TTO only had inhibition zones against Bacillus subtilis. Conclusion: In vitro, Homegrown TTO showed the pronounced microbicidal action and the persistent inhibitory action against test microorganisms. The antimicrobial activity of it had no significant change. PartⅡInactivation of Poliovirus Type-1 by TTO Solution Objective: The aim of this work was to observe the antiviral efficacy and disinfectant capacity of homegrown TTO solution against non-enveloped Poliovirus type-1(PV1), and further gain a deeper insight into the antiviral activity of it,and realize the feasibility of homegrown TTO as disinfecting agent. Method: Viral infectivity was tested on HepG2 cell using standard microtitration assays. After PV1 contacting a time ranging from 10 to 60 mins with several concentrations of TTO, the cytopathic effect(CPE) caused by PV1 was used as the index to calculate the median tissue culture infective dose(TCID50). Finally, the PV-inactivating capacity of TTO could be objectively assayed on the basis of TCID50. Result: PV1 was completely inactivated after 40 mins exposure to 1.0% TTO;0.5% TTO reduced a 4.33 log titre and a 5.5 log titre after exposure for 40 and 60 mins, respectively. Conclusion: It was concluded that inactivation of homegrown TTO was evidently effective against PV1 in vitro, and it was suggested that the oil exhibited the significant antiviral activity. It has the great potential as disinfectant. PartⅢObservation of Antiinflammatory activity of TTO Objective: This work was focused on the observation of TTO solution inhibiting TNF-αrelease from RAW264.7 cells induced by LPS in the dose-and time-dependent manners, and the understanding of contrast of the antiinflammatory efficacy of two kinds of TTO. Method: MTT assay was used to measure effects of TTO on viability of RAW264.7. In vitro, RAW264.7 cells were pretreated with two kinds of TTO solution, and then cells were stimulated by LPS. TNF-αin the supernant was tested by ELISA. Result: In vitro, two kinds of TTO at 0.001-0.00025% showed no cytotoxicity to RAW264.7 cells.0.001-0.000125% Australian TTO significantly suppressed LPS-induced production of TNF-α. Homegrown TTO at 0.001-0.00025% significantly suppressed LPS-induced production of TNF-α. 0.00025% Australian TTO pretreating for 3h and homegrown TTO pretreating for 1h showed significant protections against the stimulations of LPS. Conclusion: In vitro, two kinds of TTO have the obvious antiinflammatory efficacy, and there was no significant difference between Australian TTO and homegrown TTO.