Antiviral activity of Rhus aromatica (fragrant sumac) extract against two types of herpes simplex viruses in cell culture.

We report on the antiviral potency of an aqueous extract of root/stem bark of Rhus aromatica (fragrant sumac extract) against herpes simplex virus type 1 and type 2 in cell culture (RC-37 cells) using a plaque reduction assay. The extract exhibited a high level of anti-HSV activity with IC50-values of 0.0005% for HSV-1 and 0.0043% for HSV-2 as well as high selectivity indices (SI) of 5400 for HSV-1 and 628 for HSV-2. In order to determine the mode of antiviral action, the fragrant sumac extract was added at different times to the cells or viruses during the viral infection cycle. At maximum non-cytotoxic concentration (0.25%), plaque formation was significantly reduced by more than 99% when herpes simplex viruses were pretreated with the plant extract for 1 h prior to cell infection. When the host cells were pretreated with the fragrant sumac extract for 1 h prior to virus infection, the infectivity of viruses was reduced by 50% for HSV-1 but only moderately for HSV-2. No antiviral effect was seen when the plant extract was added to already infected host cells. Based on these findings the plant extract seems to interact not only with the viral envelope but also with the surface of the host cells impairing the ability of herpes simplex viruses to adsorb to and penetrate into the host cells. In conclusion, the aqueous fragrant sumac extract revealed a strong antiviral activity against HSV-1 and HSV-2 in vitro.

The 40- and 90-kDa membrane proteins (ORF6 gene product) of Mycoplasma pneumoniae are responsible for the tip structure formation and P1 (adhesin) association with the Triton shell.

After Triton X-100 treatment of Mycoplasma pneumoniae cells, a portion of the adhesin P1 (transmembrane protein) proved to remain tightly associated with the Triton insoluble material (Triton shell) as shown previously by several authors. However, the spontaneous loss of two cytadherence-associated membrane proteins of 90 and 40 kDa (gene product of the open reading frame 6 of the P1 operon) in a hemadsorption-negative mutant, designated M5, resulted in a 100% release of the P1 protein into the Triton phase and in the lack of the characteristic tip-like attachment organelle of M. pneumoniae indicating an essential role of the open reading frame 6 gene product in tip structure formation.

Effect of Australian tea tree oil on the viability of the wall-less bacterium Mycoplasma pneumoniae.

In vitro assays using a variety of essential oils revealed a particularly high antibacterial effect of Australian tea tree oil (TTO) on a great number of gram-negative and gram-positive bacteria of unrelated phylogenetic origin. In the present study, the susceptibility of cell wall-less bacteria such as the human pathogenic bacterium Mycoplasma pneumoniae to Australian tea tree oil was examined. The minimum inhibitory concentration (MIC) was determined to be 0.006% (v/v) TTO for the wild type and to 0.003% (v/v) TTO for mutants of M. pneumoniae which lost the ability to adhere to host cells (cytadherence-negative). The MIC and the MBC (minimum bactericidal concentration) for M. pneumoniae are 100 times lower than those for all other eubacteria tested. Electron microscopy with negatively stained cells as well as with ultrathin sections revealed a tendency to ovoid or round cells after oil treatment whereas the untreated cells of the wild type exhibit a flask-shaped morphology with a tip-like structure at one pole of the cell. The integrity of the mycoplasmal membrane seems not to be affected by TTO since no leakage of the Mycoplasma cell was observed after oil treatment. In the HET-CAM test TTO did not show any visible signs of irritation in concentrations less than 25%. Although the active component in TTO that has anti-mycoplasmal activity is not known, it seems very promising to use TTO tentatively for mouth washing and inhalation in case of Mycoplasma-pneumoniae-infection.

Comparative study on the in vitro antibacterial activity of Australian tea tree oil, cajuput oil, niaouli oil, manuka oil, kanuka oil, and eucalyptus oil.

To compare the antibacterial activity of the Australian tea tree oil (TTO) with various other medicinally and commercially important essential myrtaceous oils (cajuput oil, niaouli oil, kanuka oil, manuka oil, and eucalyptus oil) the essential oils were first analysed by GC-MS and then tested against various bacteria using a broth microdilution method. The highest activity was obtained by TTO, with MIC values of 0.25% for Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Salmonella choleraesuis, Shigella flexneri, Bacillus subtilis, Listeria monocytogenes, Staphylococcus aureus, S. saprophyticus, and S. xylosus. It is noteworthy that manuka oil exhibited a higher activity than TTO against gram-positive bacteria, with MIC values of 0.12%. Both TTO and manuka oil also demonstrated a very good antimicrobial efficacy against various antibiotic-resistant Staphylococcus species. Pseudomonas aeruginosa was resistant to all essential oils tested, even at the highest concentration of 4%.

Degradation products of monoterpenes are the sensitizing agents in tea tree oil.

BACKGROUND: Patients using tea tree oil (TTO) topically may become sensitized to this natural remedy. More than 30 cases have been documented in the literature since 1991. OBJECTIVE: Freshly distilled, as well as oxidized TTO, some fractions, and single constituents were used for experimental sensitization in guinea pigs. TTO was stored on a window sill to study the influence of light, oxygen, and warmth. The oxidized oil and different fractions were devoted to experimental sensitization in guinea pigs to determine their sensitizing potency. Fifteen constituents were patch tested in TTO-sensitive patients to find how many may play a role as contact allergens. METHODS: Guinea pigs were sensitized by a modified FCA-method (Freund's complete adjuvant) with freshly distilled TTO, oxidized TTO, the monoterpene and sesquiterpene fraction, and 1, 8-cineole. TTO-sensitive patients were tested with 15 typical constituents and degradation products. Gas chromatographic analysis was used to detect degradation products of the deteriorated TTO. RESULTS: Fresh TTO was revealed to be a very weak sensitizing material whereas oxidized TTO was 3 times stronger. The monoterpene fraction showed to be a stronger sensitizer than the sesquiterpene fraction. All 11 patients reacted mostly with a ++-plus or even a -plus reaction to alpha-terpinene, terpinolene and ascaridol. alpha-Phellandrene became positive in four patients, myrcene in only two. Gas chromatographic analyses showed that the formation of peroxides increased within 4 days from less than 50 to more than 500 ppm. Peroxides, epoxides and endoperoxides were formed. Deterioration products of alpha-terpinene were found to be mainly p-cymene, ascaridol, isoascaridol, a ketoperoxide, and colorless crystals that likely were 1,2,4-trihydroxy menthane. The p-cymene content increased dramatically from 2% to 11.5%. alpha- and gamma-terpinene, as well as terpinolene, were reduced to one half of their former concentration. Ascaridol and isoascaridol have never before been found in TTO. CONCLUSION: Tea tree oil kept in open and closed bottles or other containers undergoes photooxidation within a few days to several months, leading to the creation of degradation products that are moderate to strong sensitizers. Peroxides, epoxides and endoperoxides, like ascaridol and 1,2,4-trihydroxy menthane, are formed. These must be considered responsible for the development of allergic contact dermatitis seen in individuals treating themselves with the oil. A test series with 15 characteristic constituents is recommended for patch testing.

In vitro effect of essential oils and isolated mono- and sesquiterpenes on Leishmania major and Trypanosoma brucei.

The effect of different essential oils as well as of isolated mono- and sesquiterpenes on the viability of bloodstream forms of Trypanosoma brucei, promastigotes of Leishmania major and human HL-60 cells was evaluated using the Almar Blue assay. Of the 12 essential oils and 8 terpenes investigated, only three essential oils, Melissa officinalis (balmmint) oil, Thymus vulgaris (thyme) oil, and Melaleuca alternifolia (tea tree) oil were about 50-fold and 80-fold more toxic to bloodstream forms of T. brucei than to HL-60 cells, respectively. Terpinen-4-ol, the main compound of the Australian tea tree oil, was even 1000-fold more toxic to trypanosomes than to the human cells. On the other hand, none of the essential oils and terpenes tested were more toxic to promastigotes of L. major than to HL-60 cells.

Pharmaceutical and medicinal aspects of Australian tea tree oil.

The essential tea tree oil has been widely used in modern medicine and cosmetics in recent years. Although there are clinical data to show the benefical effects (e.g. antiseptic, antimicrobial, antioxidative) of this oil, dose-response studies are lacking. This paper reviews the clinical use of this essential oil, especially as a topical application.