J. zyxwvuts Agric. FoodChem. zyxwvut 1989, 37, 1435-1437 1435 zyxwvutsrqpo Insect Antifeedants from zyxwv Atalantia racemosa zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHG Devanand L. Luthria, Vijayaraghavan Ramakrishnan, Girja S. Verma, Bharathi R. Prabhu, and Asoke Banerji* Seven coumarin derivatives have been isolated from the n-hexane and methanol extracts of aerial parts of zyxwvutsrqpo Atalantia racemosa Wight and Am. (Rutaceae) and tested for antifeedant activity against Spodoptera litura F. larvae. Among these, xanthotoxin is the most active and luvangetin is moderately active, while xanthyletin and racemosin are active only at higher concentrations. Rutarin, rutaretin, and umbelliferone failed to cause feeding inhibition even at a concentration of zyxwv loo0 ppm. Antifeedant activities of 17 other structurally related coumarins have also been studied, to establish structure-activity relations. Problems connected with excessive use of synthetic in- secticides have stimulated the search for alternate methods for protection of crops from insect damage. In recent years greater emphasis has been laid on integrated pest man- agement programs using behavior-modifying chemicals (Renwick and Radke, 1985). Antifeedants cause cessation of feeding by modifying gustatory behavior of insects (Warthen, 1979). Reports of isolation of insect antifeedant compounds from natural sources (Nakanishi, 1981; Van Beek and De Groot, 1986) have prompted us to screen Indian plants for insect feeding inhibitory substances. This report deals with the antifeedant activity of coumarin derivatives isolated from the plant Atalantia racemosa Wight and Am. (N.O. Rutaceae). Feeding deterrency of several related coumarins has also been studied in order to establish structure-activity relations. MATERIALS AND METHODS Instruments and Conditions. Melting points were deter- mined on Fisher-Johns melting point apparatus and are uncor- rected. UV spectra were recorded in MeOH on a Shimadzu spectrophotometer (Model 240s). IR spectra were recorded on Perkin-Elmer spectrophotometer (Model 783). Mass spectral (EIMS, direct insertion) studies were carried out on a VG Mi- cromass 7070F spectrometer at 70 eV. 'H NMR spectra were recorded on Varian EM-360 (60-MHz) spectrometer. A laboratory ultrasonic cleaner (40 kHz) was used for ultrasonic irradiation. Isolation and Identification of Feeding Inhibitors from A. racemosa. Stems and leaves (1.4 kg) of the plant A. racemosa, collected from Mahabaleshwar (Maharashtra, India), were air- dried, powdered, and extracted successively (Soxhlet) with zyxwvut n- hexane and methanol. The solvents were removed under reduced pressure, and the crude extracts were fractionated by column chromatography over silica gel and eluted with mixturea of solvents with increasing polarities (n-hexane,CHCl,, EtOAc, MeOH). The procedure for isolation and purification of the chemical con- stituents is presented in Figure 1. The structures of the isolated compounds and their derivatives are shown in Figure 2. From the n-hexane extract four compounds were isolated and identified as xanthyletin (1) (Murray, 1978),racemosin (3) (Joshi et al., 1978),luvangetin (2) (Murray, 1978),and xanthotoxin (11) (Murray, 1978). Seven compounds, four (1-3, 11) of which were present in n-hexane extract, were also isolated from methanol extract. An additional three compounds were identified as zyxwvut um- belliferone (17) (Murray, 1978), rutaretin (5) (Schneider, 1967), and rutarin (4) (Murray, 1978). Identities of all isolated com- pounds were confirmed by chemical and physical (IR, UV, 'H NMR, MS, melting point) methods and are in agreement with those reported in the literature. Preparation of Derivatives. Xanthotoxol (12). Two methods were used for the preparation of compound 12: Method A. It was prepared in 50% yield by the method de- scribed by Schonberg and Aziz (1953) using aniline hydrochloride. Chemical Ecology Section, Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Bombay 400 085, In- dia. 0021-8561/89/1437-1435$01.50/0 Scheme I. Preparation of 2-Isopropylxanthotoxol Derivatives Me2S04 or Et2S04 K2C03/acetone zyxwvutsrqponmlkjihgfedcbaZYXWV - 5 ((CCCCCC OH OR 6,R=Me 7, R = Et OR y&JO 0 15, R = Me 16, R = Et Method B. To a cold solution of xanthotoxin (11) (88 mg) in methylene chloride (3 mL) at -30 "C was added BBr3 (0.2 mL). After being stirred at room temperature for 16 h, the reaction mixture was poured into ice. Xanthotoxol (12), which separated out, was filtered. Evaporation of the methylene chloride layer gave additional quantity of xanthotoxol(l2) that was mixed with the earlier lot and crystallized from acetone: yield 66 mg (80%); mp 252-253 "C (lit. mp 251-252 "C; Livingstone, 1977). Xanthotoxol Acetate (13). Acetylation of xanthotoxol (12) with Ac20/pyridine (16 h, 30 "C) followed by the usual workup furnished compound 1 3 mp 176-179 "C; 'H NMR (CDClJ 6 2.50 H-5), 7.56 (s, 1, H-4), 6.83 and 7.70 (furan ring protons). Xanthotoxol Ethyl Ether (14). A mixture of compound 12 (60 mg), K&03 (500 mg), and diethyl sulfate (0.2 mL) in acetone (10 mL) was irradiated with ultrasound at room temperature until the reaction was complete (monitored by TLC, 3 h). The reaction mixture was worked up in the usual way. Compound 14 was purified by preparative TLC followed by crystdlization (ace- toneln-hexane): yield 48 mg (71%); mp 104-106 "C (lit. mp 104-106 "C; Banerjee et al., 1982). Rutaretin 9-Methyl and BEthyl Ethers (6 and 7). These compounds were prepared by sonochemical 0-alkylation of ru- taretin (5) with dimethyl suMate/diethyl sulfate as described above (Scheme I). Rutaretin 9-methyl ether (6): yield 72%; mp 132 "C (lit. mp 132-133 "C; Schneider et al., 1967). Rutaretin 9-ethyl ether (7): yield 75%; crystallized from EtOAcln-hexane as colorless needles; mp 102-104 "C; IR, Y , (KI3r pellet) 3470,2980, 1710,1620,1585,1485,1430,1290,1150,1090, 1085,1015 cm-'; UV, A , (methanol) 252 nm (e 4557), 262 (e 4842), 334 (e 16 145); 'H NMR (CDC13) 6 1.24 and 1.37 (2 s, 6, C(CHJZ), 1.40 (t, 3, (9, 3, COCH3), 6.38 (d, 1, J = 10 Hz, H-6), 7.80 (d, 1, J = 10 Hz, OCHZCH3), 1.97 (9, 1, OH), 3.23 (d, 2, J = 9 Hz, C-3 CH2), 4.30 (9, 2, J = 7 Hz, OCHZCH,), 4.76 (t, 1, J = 7 Hz, C-2 CH), 6.18 (d, 1, J = 10 Hz, H-6), 6.94 ( ~ , l , H-4), 7.57 (d, 1, J = 10 Hz, H-5); MS (70 eV) m/e 290 (M+),275,273,257,232,230,219,204,203, 59. Anal. Calcd for C16H1805: C, 66.18; H, 6.25. Found C, 66.32; H, 6.31. 2-lsopropyZxanthotoxin (15). A mixture of compound 6 (60 mg) in benzene (5 mL) and p-toluenesulfonic acid (60 mg) was refluxed. The completion of the reaction was monitored by TLC (4 h). The reaction mixture was successively washed with aqueous NaHCO,, water, and brine. The dried (Na2S0,) organic layer on removal of solvent gave crude compound 15, which was purified by preparative TLC (CHC13, double run) followed by crystalli- 0 1989 American Chemical Society