Curcuma Longa Eo

J. Agric. Food Chem. 1982, 30,290-292

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Isolation, Purification, and Characterization of Insect Repellents from Curcuma longa L. Helen C. F. Su,* Robert Horvat, and Ghulam Jilani'

Two compounds were isolated from Curcuma longa L. and identified from their spectral characteristics as 2-methyl-6-(4-methylphenyl)-2-hepten-4-one (ar-turmerone) and 2-methyl-6-(4-methyl-l,4-cyclohexadien-l-yl)-2-hepten-4-one (turmerone). ar-Turmerone and turmerone gave an average 62.9% (class IV)and 43.1% (class 111) repellency, respectively, to TriboZium castaneum (Hbst.)after 8 weeb of study. Turmerone was unstable thermally and also at ambient temperature in the presence of air, yielding its dimer or the more stable ar-turmerone.

Tumeric, Curcuma longa L., is a tropical herb of the Zingiberaceae family indigenous to southern Asia. The aromatic yellow powder from its mature rhizomes was used in Asian countries for many centuries as a yellow vegetable dye for silks and cottons. It is still used in foods as a condiment, particularly as an essential ingredient of curry powder, in medicine as a stomachic, carminative, anthelmintic, laxative, and cure for liver ailment, and also as an ant repellent in India (Sreenivasamurthy and Krishnamurthy, 1959; Watt and Breyer-Brandwijk, 1962). The strong coloring pigment in turmeric contains curcumin, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, and two other curcuminoids (Srinivasan, 1953; Lubis, 1968; Shankaracharya and Natarajan, 1974; Krishnamurthy et al., 1976). The red-yellow essential oil of turmeric, either from steam distillation or from an oil-selecting solvent extraction, contains d-a-phellandrene, d-sabinene, zingiberene, borneol, l,&cineole, turmerone, ar-turmerone, sesquiterpene alcohols, a-and y-atlantone, and bisabolene (Gildemeister and Hoffmann, 1956; Mima, 1959; Shankaracharya and Natarajan, 1974; Salzer, 1975 Govindarajan, 1980). Shankar et al. (1980) conducted feeding toxicity studies of turmeric and its alcohol extract in rats, guinea pigs, and monkeys. The results indicated that turmeric is nontoxic even at the very high level tested. There was absolutely no mortality or any morphological and histological abnormalities in the experimental animals at 2.5 g of turmeric/kg of body weight which corresponds to a maximum consumption of 5 g/day for an adult human with an average body weight of 70 kg. It is the practice in some southern Asian countries; i.e., India and Pakistan, to store rice or wheat by mixing it with 2% of turmeric powder (Chatterjee, 1980). In this paper, we report the isolation, purification,and identification of the repellent components of turmeric to Tribolium castaneum (Hbst.). MATERIALS AND METHODS

Extraction of Turmeric. Powdered turmeric (imported from India) was purchased from Lex Enterprise,

Stored-Product Insects Research and Development Laboratory, Agricultural Research, Science and Education Administration, US.Department of Agriculture, Savannah, Georgia 31403 (H.C.F.S. and G.J.), and Richard B. Russell Agricultural Research Center, Agricultural Research, Science and Education Adminstration, US. Department of Agriculture, Athens, Georgia 30604 (R.H.). lFulbright-Hays Predoctoral Research Associate, 1978-1979. Present address: Honeybee Management, Pakistan Agricultural Research Council, Islamabad, Pakistan.

Atlanta, GA. One kilogram of the powder was extracted in a Soxhlet extractor with petroleum ether (bp 30-60 "C) for 24 h. The petroleum ether solution was concentrated under reduced pressure in a rotary evaporator to obtain the crude turmeric extract. Liquid Column Chromatographic (LCC) Fractionation of Crude Turmeric Extract. Step 1. Each 1.41.6-g portion of the crude extract was placed on a column (40 X 2.0 cm i.d.) of silica gel (70-230 mesh; EM Reagent; extra pure) and eluted with chloroform. A total of 120 2-mL fractions was collected. After the solvent was removed, every third fraction was spot tested by TLC (see below for procedure). The fractions possessing the same Rr values were combined, and each combined fraction was bioassayed for repellency to T. castaneum. The insect active fraction was further fractionated. Step 2. Each 150-160-mg sample of the active fraction from step 1was further separated by column chromatography in a 40 X 1.2 cm i.d. column of silica gel and eluted with benzene. A total of 90 2-mL fractions was collected. TLC analysis was made on every third fraction. The fractions with only Rf 0.25-0.28, the mixture of R 0.25-0.28 and 0.30-0.33, and only R 0.30-0.33 were com6ined separately. The two pure combined fractions were bioassayed. Thin-Layer Chromatographic Analysis of LCC Fractions. Brinkman EM reagent, precoated silica gel G FZu,20 X 20 cm analytical chromatoplates were used. A small sample of each selected fraction was applied on spots 2.5 cm above the lower edge and 1.5 cm from each other. Each plate was developed in benzene and then examined under UV at 254 nm. High-Performance Liquid Chromatographic Purification. A Waters Associates Model ALC/GPC 244 high-pressure liquid chromatograph with a Model 6000A pump, a U6K injector, an R401 differential refractometer, and a Model 440 UV detector with a 300 X 7.8 mm i.d. pBondapak C18column (octadecyltrichlorsilanecovalently bonded to lo-" pPorasil packing) was used. Methanol-water ( 8 2 by volume, degassed) was used as the eluting system. The column effluent was monitored at 254 nm (2.0 AUFS), and the response was recorded on a Houston Omniscribe Model B-5217-1 recorder. Each of the two LCC separated components was dissolved individually in methanol to obtain the concentration of approximately 20 Mg/pL and filtered through a Waters Associates sample clarification kit with 0.5-pm Millipore organic filter system. For each run, a 5-pL aliquot of the stock solution was injected onto the column with the flow rate of the eluting solvent at 1.5 mL/min. The desired peak of the compound as indicated from the recorder was recycled through the column once, and the effluent of the recycled peak was collected. The process was repeated

This article not subject to U S . Copyright. Published 1982 by the American Chemical Society