Agric. Biol Chem., 48 (12), 3147-3149, 1984 3147

Note none of the NMR spectral data to explain how this structure has been reported. The AHand 13C NMRspectra were therefore recorded and analyzed (Table I). The Desacetylisotenulin, a Molluscicide lactone ring closure to C-8a concurs with the coupling from the Desert patterns for 7-H, 8-H and 9-H. The aromatic solvent- ramosissima induced shifts in the XH NMR (^<5=^C5D5N-^CDC13) are also compatible with the relative configuration de- picted in 2. The significant low field shift of H-ll Isao Kubo and Takeshi Matsumoto (+0.39ppm) indicates that this proton and the hydroxyl group at C-6 are syn, whereas the moderate low field shifts Division of Entomology and Parasitology, of H-7 (+0.1 ppm) and H-l (+0.09ppm) compared with College of Natural Resources, that of Me-15 (+0.14ppm) indicate that both H-7 and H- University of , Berkeley, California 94720, U.S.A. Table I. JH and 13C NMRSpectral Data of Received May 25, 1984 Desacetylisotenulin

Proton In CDC13 Carbon In C5D5N H-l 2.56(1H,ddd,2.0,2.7,10.7) £"* .jjH Desacetylisotenulin was isolated as a molluscicide from the desert plant , whose chemical H-2 7.67(1H,dd,2.0,6.0) Z" ' components* have not before been examined. We de- H-3 6.14(lH,dd,2.7,6.0) ~ *£' scribe here its spectral examination and biological activity. H-6 4.15 (1H, dd, 2.9, 6,8) ' Schistosomiasis, a parasitic disease carried by snail H-7 2.15(lH,m) " ' vectors, is one of the largest of human health problems. H-8 4.73(1H,ddd, 3.5, 10.8, ll.1) Z,. . H-9 2.50(1H, ddd, 3.5, 4.7, 13.4) Z, During the past decade, numerous schistosomiasis control H-9 1.28(lH,m) " ' projects in the Third World have shown that control of H-10 2.15(lH,m) ' snail vectors by molluscicides can be a rapid and efficient Me-14 1.22(3H,d,6.7) r"1" ^ means for reducing or eliminating the transmission of this Me-15 1.20(3H,s) £' ^ disease.1* Molluscicides of plant origin are currently re- H-ll 3.09(1H,dq, 12.7,6.9) ^" 7 ' ceiving considerable attention in the hope of their rel- Me-13 1.25(3H,d,6.9) lg' a atively harmless and biodegradative properties.2* In our OH 2.70 (1H, d, 2.9) ' continuing search for naturally occurring mollus- cicides,3 ~5) we have examined the desert plant Psathyrotes ramosissima (Compositae),6) whose chemistry has not been previously studied. Assignments may be interchanged. The crude methanol extract of fresh of P. ramo- 14 sissima showed molluscicidal activity against the South 2M^ 9 American snail Biomphalaria glabratus, hence further separation was carried out while monitoring with this bioassay.7) After fractionation into hexane, ethyl acetate and water-soluble portions, the active ethyl acetate extract waschromatographed on silica gel and the major active 13/ principle was purified to give a colorless crystalline com- 1 pound. This was found to be identical with authentic desacetylisotenulin, a pseudoguaianolide type of sesquiter- pene lactone previously isolated from bigelovii,8) in the following respects: mp 225°C (EtOH), [a]f>° - 15° (c=0.31, CHCI3), UV (EtOH) 225nm (e: 8700), IR q-0.2 +0.14 +0.09 (CHCI3) 3550, 1770, 1705 and 1582cm"1, EIMS m/z 264 +0.03 >/ p\l H-0.2 1 q [M]+ and cochromatography on TLC (silica gel and RP- 18). The CDspectrum showeda negative Cotton effect for H^^\ |^^J1 /H+0.39 the n-n* transition of the a, /?-unsaturated ketone, with As-IA (333nm), which is characteristic of pseudo- -0.15 ii "01H +0-23H Vu guaianolides having the trans-ring fusion at C-l/C-5.9) +0.09 +0-1 3 t° Although the structure of desacetylisotenulin has been 2 proposed as l,10) in connection with 3-bromoisotenulin whose structure had been established by X-ray analysis,11* C a6 (c5d5n-cdci3)] 3148 I. Kubo and T. Matsumoto

Table II. Effect of Deacetylisotenulin on Growth of Lettuce and Rice Seedlings Length (mm)

Lettuce Rice

Root Hypocotyl Shoot Root 0 1 3 10 30 100

12.09±0.62 9.85±0.50

0.70±1.0618.00±0.5020.20±1.1317.40±0.8816.13±0.83 35.90±3.0034.33±3.66

31.60±2.5026.40±3.4910.09±0.84 6.03±0.504.42±0.37 33.80±2.27 300 31.50±2.6138.50±2.6729.60±4.3024.44±4.33

17.90±2.3215.90+1.40

1 are anti the-hydroxyl group. Thus, the XHNMRdata with methanol. The extracts were concentrated to afford are in full agreement with the relative stereochemistries an oily residue. The residue was diluted with H2O, ex- of6-OH and ll-Me as shown in 1. tracted with hexane and then with ethyl acetate. The The LC50-value, the lethal dose for 50% fatality, of ethyl acetate extract (2.2g) was chromatographed on desacetylisotenulin against the snail B. glabratus was silica gel with CHCl3-MeOH (50: 1) to give desacetyl- 20ppm. Although two pseudoguainanolides having an isotenulin (290 mg). exo-methylenelactone moiety, damsin and ambrosin,2) have been known as potent molluscicides (8.15~ Acknowledgments.The authentic sample of desacetyl- 13.5ppm), the present result clearly indicates that the isotenulin was kindly provided by Professor W. Herz. exo-methylenelactone moiety is not essential for mol- Wethank Dr. I. Holden for NMRmeasurements and luscicidal activity. Dr. K. Tsujimoto for MSmeasurements. Finally we thank In desert plants, it might be expected that considerable Dr. M. Taniguchi for plant growth bioassay. competition for the limited water available in the soil would result in the development of manycompetitive effects, including allelopatyl.12) Hence, we investigated the REFERENCES possibility that desacetylisotenulin might have an in- hibitory effect on the growth of lettuce and rice seedlings. 1) F. S. McCullough, Ph. Gayral and J. D. Christie, The bioassay was carried out according to the methods Bull. W. H. O., 58, 681 (1980). previously reported,13) with the results in Table II. 2) H. Kloos and F. S. McCullough, Bull. W. H. O., 59, Desacetylisotenulin significantly inhibited the root growth 834 (1981). of lettuce at a concentration of 30 /ig/ml, but did not show 3) I. Kubo and A. Matsumoto, J. Agric. Food Chem., an inhibitory effect on rice root growth at the same 32, 687 (1984). concentration. 4) I. Kubo, T. Matsumoto, J. A. Klocke and T. Kamikawa, Experientia, 40, 340 (1984). EXPERIMENTAL 5) I. Kubo, T. Matsumoto, A. B. Kakooko and N. K. Mubiru, Chem. Lett., 979 (1983). Melting points were determined on a Sybron 6) R. Ornduff, P. H. Raven, D. W. Kyhos and A. R. Thermolyne Mp-12615 and are uncorrected. UVspectra Kruckeberg, Am. J. Bot., 50, 131 (1963). were recorded on a Hitachi UV-100-80 spectrophotometer 7) K. Nakanishi and I. Kubo, Israel J. Chem., 16, 28 with a 10mmcell. IR spectra were taken on a Perkin- (1978). Elmer 737 B. MSwas obtained with a Hitachi RMU6- 8) B. A. Parker and T. A. Geissman, J. Org. Chem., 27, MGspectrometer. CDmeasurement was performed using 4127 (1962). Although Psathyrotes is usually placed a Jasco J-40 spectropolarimeter. *H and 13C NMRspectra in Senecioneae, Ornduff et al.6) put it in were recorded on a Bruker FT-250 instrument, using TMS based on the chromosome number. The present as an internal standard. TLCwas carried out using a finding of desacetylisotenulin in both genus Macherey-Nagel Poligram Sil G/UV254 TLCplate, a Psathyrotes and Helenium supports this from the Merck HPTLC pre-coated plate and an RP-18 F 254 chemotaxonomic standpoint. 9) T. G. Waddell and T. A. Geissman, Phytochemistry, TLCplate. 8, 2371 (1969). Isolation. The fresh plants (360g) were collected in 10) N. H. Fischer, E. J. Olivier and H. D. Fischer, Prog. Death2Valley, California in February 1983 and extracted Chem. Org. Nat. Prod., 38, 47 (1979). Molluscicide from the Desert Plant 3149 ll) H. Haque, D. Rogers and C. N. Caughlan, /. Chem. 13) S. Kamisaka, Plant and Cell PhysioL, K 747 (1973); Soc, Perkin Trans. 2, 223 (1974). M. Taniguchi, T. Kamikawa, Y. Fujiwara and Y. 12) J. B. Harborne, "Introduction to Ecological Satomura, Phytochemistry, 15, 29 (1976). Biochemistry," Academic Press, 1982, pp. 212~214.