No direct hepatotoxic potential following a multiple-low dose paraquat exposure in rat as related to its bioaccumulation.

Paraquat (PQ) is a well-known toxic bipyridyl herbicide commonly used in agricultural countries. Pulmonary toxicity is the main cause of death but damage to other organs has also been reported. PQ is also classified as a "direct hepatotoxicant" following an acute high dose exposure. The evidence of multi-low dose toxicity of PQ was scarce. Therefore, the aim of this study was to examine the effect of multiple low doses of PQ on the liver function and xenobiotic-metabolizing enzyme activities including CYP1A1, 2E1, and 3A4, and to correlate the effects with its tissue accumulation. PQ, at the dose range 4.0-6.0 mg/kg day, was subcutaneously administered to male Wistar rats for seven consecutive days. The prominent feature of toxic response was lung toxicity. Interestingly, PQ-treatment caused a dose- and time-dependent reduction of plasma transaminase activity. Hypobilirubinemia and hypoalbuminemia were also observed without significant alteration in the liver morphology. Of all the xenobiotic-metabolizing enzymes being studied, only the activity of CYP1A1-related 7-ethoxyresorufin-O-deethylase was reduced following the highest dose of PQ administration. Plasma and tissue concentrations and accumulation of PQ analyzed by HPLC were dose-dependent showing much higher concentration (approximately 13 times) in the lung than that in the liver whereas it was undetectable in the plasma at the same time point. It can be concluded that multi-low dose PQ might affect certain synthetic function of the liver or activity of some hepatic xenobiotic-metabolizing enzymes. Minimal PQ accumulation in the liver is one of the explanations for the lack of cytotoxic hepatic injury in this study. Plasma PQ concentration may not be a good marker of exposure and toxicity after a prolonged exposure to PQ.

Repellent activity of essential oils against cockroaches (Dictyoptera: Blattidae, Blattellidae, and Blaberidae) in Thailand.

Seven commercial essential oils extracted from the plant species Boesenbergia rotunda (L.) Mansf., Citrus hystrix DC., Curcuma longa L., Litsea cubeba (Lour.) Pers., Piper nigrum L., Psidium guajava L. and Zingiber officinale Roscoe, and naphthalene as a control, were evaluated for repellent activity against the three cockroach species Periplaneta americana (L.), Blattella germanica (L.) and Neostylopyga rhombifolia (Stoll) under laboratory conditions. The essential oil derived from Citrus hystrix showed the best repellency over other candidate essential oils and naphthalene. The essential oil of Citrus hystrix exhibited complete repellency (100%) against P. americana and B. germanica, and also showed the highest repellency (among the essential oils tested) of about 87.5% against N. rhombifolia under laboratory conditions. In the field, Citrus hystrix essential oil formulated as a 20% active ingredient in ethanol and some additives provided satisfactory repellency of up to 86% reduction in cockroaches, mostly P. americana and N. rhombifolia with a residual effect lasting a week after treatment. Citrus hystrix essential oil has good potential for being used as a cockroach repellent. Further improvements in efficacy and residual activity may be realized with appropriate formulations.

Field evaluation of deet, Repel Care, and three plant based essential oil repellents against mosquitoes, black flies (Diptera: Simuliidae) and land leeches (Arhynchobdellida: Haemadipsidae) in Thailand.

Diethyl methyl benzamide, or deet, a commercial plant-based repellent (Repel Care), and essential ils from 3 species of plants (finger root rhizomes, guava leaves, and turmeric rhizomes), steam distillated and formulated as insect repellents, were evaluated in the field on human volunteers against hematophagous mosquitoes, black flies, and land leeches in Thailand. Field trials were conducted against wild mosquitoes in Bang Bua Thong District, Nonthaburi Province, and in the Thap Lan National Park Headquarters, Nadee District, Pranchinburi Province; anthroophilic black flies (Diptera: Simuliidae) at the Forestry Fire Control Station in Doi Inthanon National Park, Chomthong district, Chiang Mai Province; and land leeches (Arhynchobdellida: Haemadipsidae) in the Khao Yai National Park, Pak Chong District, Nakhon Ratchasima Province. The 3 experimental plant-based essential oil formulations as well as Repel Care and deet provided complete protection from mosquito landing and biting for up to 9 h (duration of the experiment). Similar results were obtained with the 5 products against black flies, providing 100% protection for 9 h but 96-82% protection after 10 and 11 h posttreatment. The 5 repellent products also provided 100% protection against land leeches for at least 8 h. Thi is the 1st report of repellency of plant-based repellents against black flies and land leeches in Thailand. The identification and availability of inexpensive sources of plant-based oils, i.e., finger root rhizomes, guava leaves, and turmeric rhizomes providing long-lasting repellency against blood-sucking organisms are promising leads into commercial production of relatively safe and effective repellents.

Repellency of essential oils extracted from plants in Thailand against four mosquito vectors (Diptera: Culicidae) and oviposition deterrent effects against Aedes aegypti (Diptera: Culicidae).

In this study we evaluated and reported repellent effects of essential oils from Thai plants against 4 mosquito vectors: Aedes aegypti, Ae. albopictus, Anopheles. dirus and Culex quinquefasciatus under laboratory conditions using human volunteers. The essential oils were extracted from 18 plant species, belonging to 11 families, and the oils were then prepared as 10% solution in absolute ethanol with additives. Two chemical repellents, deet and IR3535, were also prepared in the same formulation as the essential oil repellents and tested for repellency as controls. The essential oils were also evaluated for oviposition deterrent effects against Ae. aegypti under laboratory conditions. The results show night-biting mosquitoes (An. dirus and Cx. quinquefasciatus) and Ae. albopictus were more sensitive to all the essential oils (repellency 4.5 - 8 hours) than was Ae. aegypti (repellency 0.3 - 2.8 hours), whereas deet and IR3535 provided excellent repellency against all four mosquito species (repellency 6.7- 8 hours). All essential oils exhibited oviposition deterrent activity against Ae. aegypti with various degrees of repellency ranging from 16.6 to 94.7%, whereas deet and IR3535 had no repellency. The present study demonstrates the potential for using essential oils as mosquito repellents and oviposition deterrents. These findings may lead to new and more effective strategies for protection from and control of mosquitoes.

Chronic toxicity study of Portulaca grandiflora Hook.

We investigated the toxic effects of Portulaca grandiflora aqueous extract given to male and female Wistar rats for 6 months. The rats were divided into five groups of each sex that were control groups, three experimental groups and recovery groups. The control groups received 5 ml of distilled water/kg per day. The experimental groups were orally given the water extract of Portulaca grandiflora at doses of 10, 100 and 1000 mg/kg per day. The recovery groups received 1000 mg/kg per day for 6 months and were continued husbandry without giving the extract for further 14 days. Changes in the body weights, actual and relative organ weights were not significantly demonstrated in all groups throughout the study. No significant alteration in hematological, biochemical and histopathological parameters was observed in all female groups given the extract. It was found that any significant changes in hematological and biochemical parameters in the male rats at the doses of 100 and 1000 mg/kg per day were not dose-related. In addition, no histopathological lesions were observed in the male animals. Our results suggested that the water extract of Portulaca grandiflora at the doses given in the study did not induce any detrimental effects in the rats.

Molecular evaluation of extracellular activity of medicinal herb Clinacanthus nutans against herpes simplex virus type-2.

Clinacanthus nutans (Burm. f.) Lindau (C. nutans), a medicinal herb belonging to the family Acanthaceae, has traditionally been used in herpes simplex virus (HSV) treatment in Thailand. Clinical trials have indicated that topical preparations produced from its extracts were effective in HSV-2 treatment. However, there is no clear evidence of the mechanism of action or a molecular target of C. nutans. In this study, the extracellular activity of C. nutans extracts against HSV-2 infected on HEp-2 cells was investigated in terms of its molecular aspects. HSV-2 was treated with the extracts and adsorped into the HEp-2 cells. After infection, HSV-2 DNA quantities in the infected cells were assessed and compared by the quantitative dot blot hybridisation technique. The results showed that treating the viruses with either less or more highly purified extracts before infection resulted in great reductions of viral infectivity. Further investigation was performed by Western blot analysis to determine the activities of the extracts on the viral proteins. At least eight viral proteins of the infected cell proteins (ICP) and some structural proteins, including 146, 125, 78, 69, 55, 44, 40 and 20 KDa proteins, were depleted and reduced gradually with higher and lower concentrated herb extracts, respectively. These suggest that the C. nutans extracts highly inactivated or inhibited HSV-2 before infection.