Thidarat Boonruad

Bio: Thidarat Boonruad is an academic researcher. The author has contributed to research in topics: Culex quinquefasciatus & Aedes aegypti. The author has an hindex of 6, co-authored 9 publications receiving 392 citations.

Repellency of essential oils extracted from plants in thailand against four mosquito vectors (diptera: culicidae) and oviposition deterrent effects against aedes aegypti (diptera: culicidae)

Abstract: 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.

Mosquito larvicidal activity of aqueous extracts of long pepper (Piper retrofractum vahl) from Thailand.

Abstract: Aqueous extracts of nine medicinal plants were bioassayed against larvae of Culex quinquefasciatus Say and Aedes aegypt (L.). Among these plants, the long pepper, Piper retrofractum Vahl (Piperaceae), showed the highest level of activity against mosquito larvae. To gain more information on larvicidal activity of P. retrofractum, fresh fruits of this plant were extracted in water and the extracts made into powder and bioassayed against 3rd and 4th instar larvae of Cx. quinquefasciatus and Ae. aegypti in the laboratory. Extracts of unripe (001/3) and ripe (002/3 and 001/4) fruits showed different levels of activity against Cx. quinquefasciatus larvae. Extracts 001/3 and 002/3 were equi-toxic to a Bacillus sphaericus resistant and susceptible strains, both from Thailand. The ripe fruit extract 002/3 was somewhat more active against Ae. aegypti than Cx. quinquefasciatus. Another ripe fruit extract (001/4) was much more toxic to both mosquito species. Diluted solutions of the solid extract (002/3) in distilled water lost their larvicidal activity upon aging. Loss of activity at 25 degrees C was greater than that stored at 4 degrees C, and greater in water than in acetone solution.

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

Abstract: 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.

Abstract: 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.

Screening of Medicinal Plants for Antimicrobial Activity

Abstract: Production of antimicrobial drugs from Thai medicinal plants is one way of reducing importation of drugs. A preliminary antimicrobial screening of medicinal plants was done by assaying 48 extracts of 20 medicinal plants from 10 families by agar dilution method. The agar dilution method was carried out on bacteria a total of 21 species 24 strains and 1 strain of fungus. Seventeen plants (35 samples) showed antimicrobial activity. However, none of the extracts was able to inhibit all tested strains. Seven medicinal plants showed antimicrobial activity on many strains and should do further investigation. These are Ka-meng (Eclipta prostrata L.), Kra-chiap-daeng (Hibiscus sabdariffa L.), Do-dok-khao (Elephantopus mollis H.B.K.),Pip (Millingtonia hortensis L.f.), Phak-khom-hin (Boerhavia diffusa L.), Yom-hin (Chukrasia tabularis A. Juss.) and Ngueak-pla-mo (Acanthus ebracteatus Vahl). Key words : Antimicrobial activity, Medicinal plants

Plant extracts as potential mosquito larvicides

Abstract: Mosquitoes act as a vector for most of the life threatening diseases like malaria, yellow fever, dengue fever, chikungunya ferver, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management (IMM), emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain and adverse effects on environmental quality and non target organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on phytochemical sources and mosquitocidal activity, their mechanism of action on target population, variation of their larvicidal activity according to mosquito species, instar specificity, polarity of solvents used during extraction, nature of active ingredient and promising advances made in biological control of mosquitoes by plant derived secondary metabolites have been reviewed.

Biological properties of essential oils: an updated review

Abstract: In the last few years more and more studies on the biological properties of essential oils have been published and it seemed worthwhile to compile the studies of 2009, 2008 and the second part of 2007. Such an overview covering the scientific literature mainly from 2000 onwards, up to the first half of the year 2007, has been published recently. The focus of this overview lies on the anti-nociceptive, anticancer, anti-inflammatory, penetration-enhancing, insect repellent, antiviral and antioxidative properties of essential oils. Many essential oils have been used for centuries in folk medicine and in recent years the biological properties of various essential oils have been proved by a number of studies. Their use in the treatment of pain, inflammation, viral diseases and cancer and their potential to enhance the penetration of other drugs, their insect repellent activity and their antioxidative effects were confirmed. Nonetheless, more studies are necessary to analyse the biological properties of other essential oils or to prove their mechanism of action. Copyright © 2010 John Wiley & Sons, Ltd.

Piper Species: A Comprehensive Review on Their Phytochemistry, Biological Activities and Applications.

Abstract: Piper species are aromatic plants used as spices in the kitchen, but their secondary metabolites have also shown biological effects on human health. These plants are rich in essential oils, which can be found in their fruits, seeds, leaves, branches, roots and stems. Some Piper species have simple chemical profiles, while others, such as Piper nigrum, Piper betle, and Piper auritum, contain very diverse suites of secondary metabolites. In traditional medicine, Piper species have been used worldwide to treat several diseases such as urological problems, skin, liver and stomach ailments, for wound healing, and as antipyretic and anti-inflammatory agents. In addition, Piper species could be used as natural antioxidants and antimicrobial agents in food preservation. The phytochemicals and essential oils of Piper species have shown strong antioxidant activity, in comparison with synthetic antioxidants, and demonstrated antibacterial and antifungal activities against human pathogens. Moreover, Piper species possess therapeutic and preventive potential against several chronic disorders. Among the functional properties of Piper plants/extracts/active components the antiproliferative, anti-inflammatory, and neuropharmacological activities of the extracts and extract-derived bioactive constituents are thought to be key effects for the protection against chronic conditions, based on preclinical in vitro and in vivo studies, besides clinical studies. Habitats and cultivation of Piper species are also covered in this review. In this current work, available literature of chemical constituents of the essential oils Piper plants, their use in traditional medicine, their applications as a food preservative, their antiparasitic activities and other important biological activities are reviewed.