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constituents in T. laurifolia aqueous extract. using a rotary evaporator to obtain dried extract at a
The water extract of T. laurifolia has been yield of 23.283 percent (w/w). Prior to dosing in ani-
demonstrated to reduce cholinergic effects and de- mals, the dried extract of T. laurifolia (TLE) was then
crease mortality in rats treated with folidol, an orga- dissolved in distilled water and adjusted to the de-
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nophosphate insecticide. Tea from the leaves of this sired concentrations for toxicity study.
plant has also been shown to effectively reduce in-
Laboratory animals
secticide residue levels in the blood circulation of ag-
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riculturists. Pramyoththin et al. reported that the Ninety male Wistar rats weighing 200-220 g and
aqueous extract of T. laurifolia leaves was found to an equal number of female rats weighing 170-190 g
possess hepatoprotective activity against ethanol-in- were purchased from the National Laboratory
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duced liver injury both in vitro and in vivo. The Animal Center, Mahidol University, Nakhon Pathom
above-mentioned reports suggest that rang chuet has Province and used in this study. The animals were
the potential to be used as an herbal detoxifying agent. housed in a hygienic conventional animal room of
However, little toxicological data, especially in labo- the laboratory animal center, Department of Medical
ratory animals, have been reported. A 28-day re- Sciences, where the environment of the room was
peated dose toxicity study of the T. laurifolia aqueous maintained at 25±1˚C with 60 percent humidity and
extract at an oral dose of 500mg/kg revealed that the 12 hours of a light-dark cycle. Prior to the chronic
extract did not cause any histological changes of the toxicity study, the animals were acclimatized in that
organs; however, it may affect some hematological environment for two weeks and they were reared on
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values and kidney weights. In this study, we inves- a commercially pelleted diet and clean water provided
tigated the chronic toxicity of T. laurifolia water ex- ad lib. This study was approved by the Institutional
tract in rats in order to obtain more toxicological in- Animal Care and Use Committee, Department of Medi-
formation to assure the safety of this plant. cal Sciences.

Materials and Methods Chronic toxicity study

Wistar rats were randomly divided into five
Preparation of Thunbergia laurifolia extract groups of 15 animals/sex each. Group 1 received 10

Leaves of Thunbergia laurifolia Lindl. (Acan- ml/kg per day of distilled water. Groups 2 to 6 were
thaceae) were collected from a cultivated area in orally administered a solution of TLE at doses of 20,
Pitsanulok Province, Thailand. A voucher specimen 200, 1000, 2000 and 2000 mg/kg/day respectively, for
(Bansiddhi 45-11) was deposited at the Botanical Labo- six months, which were equivalent to 1, 10, 50 and
ratory, Medicinal Plant Research Institute, Nonthaburi 100 times the therapeutic dose (5 grams of dried T.
Province. The botanical identification was determined laurifolia powder/day/person). After the six-month
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by following the description of Backer and Bakhuizen period of TLE treatment, only Group 6 (2000R) was
and compared with authentic specimens (Lakshna- reared for two more weeks without TLE administra-
kara 1368) at the Bangkok herbarium (BK), Depart- tion in order to observe the recovery or delayed ef-
ment of Agriculture, Ministry of Agriculture and Co- fects of the extract. During the period of the experi-
operatives, Bangkok, Thailand. ment, body weight and food consumption were re-
The leaves of Thunbergia laurifolia were first corded weekly and the rats were closely observed for
washed, then dried in a hot-air oven at 40˚C and general appearance, behavior and signs of abnormal-
pulverized into coarse powder. Three hundred grams ity. At the end of the 180-day treatment period, the
of T. laurifolia powder were extracted with 300 ml of animals were fasted for 16 hours before being sacri-
distilled water by reflux method twice, each for 2 ficed with diethyl ether inhalation. Laparotomy was
hours. The filtrate was evaporated at low pressure performed and blood samples were collected from the