Joseph J. Hoffmann

Silphinene sesquiterpenes as model insect antifeedants.

Silphinene sesquiterpenes are established chrysomelid antifeedants. In this work, nine silphinene analogs, 11β-acetoxy-5α-angeloyloxysilphinen-3-one (1), 11β-acetoxy-5α-tigloyloxysilphinen-3-one (2), 11β-acetoxy-5α-iso- butyryloxysilphinen-3-one (3), 11β-hydroxy-5α-angeloyloxysilphinen-3-one (4), 11β,5α-dihydroxysilphinen-3-one (5), 11β,5α-diacetoxysilphinen-3-one (6), 5α,11β-diisobutyryloxysilphinen-3-one (7), silphinen-3,5,11-trione (8), and O-methyl-5-epicantabrenolic acid methyl ester (10), and a presilphiperfolane sesquiterpene (9) were tested against several divergent insect species, including the lepidopteran Spodoptera littoralis, the chrysomelid Leptinotarsa decemlineata, and five aphid species, and their antifeedant effects were compared with those of picrotoxinin, a GABA-antagonist, and thymol, an allosteric modulator for insect GABA receptors. All insects tested responded to at least one silphinene analog and/or GABA antagonist. Compound 3 and thymol were effective antifeedants against all species tested except S. littoralis, with varying potencies according to their feeding ecologies. The toxicity of these compounds was species-dependent and did not correlate with their antifeedant effect.

Survey of biocrude-producing plants from the southwest

One hundred ninety-five species of plants native to the southwestern United States and northwestern Mexico were surveyed for potential feedstocks for biocrude production in arid lands. Biocrude is the hydrocarbon and hydrocarbonlike chemical fraction of plants which may be extracted by organic solvents and upgraded to liquid fuels and chemical feedstocks. Plants were evaluated using a set of models which provide estimates of oil and energy production costs. Plants producing either latex or resinous exudates had the highest percentage of high energy extracts. Total extracts were highest in smaller, potentially less productive plants. The optimum combination of percentage biocrude and potential yield occurred in plants of intermediate size having higher than average extractables. High biomass yields do not appear necessary for the economic production of biocrude in irrigated, arid regions. Several desert plants might produce biocrude for between

POTENTIAL ANTIMICROBIAL ACTIVITY OF PLANTS FROM THE SOUTHWESTERN UNITED STATES

10–15 per million BTU without by-product credits.

Grindelane diterpenoids from Grindelia campórum and Chrysothamnus paniculatus

Organic solvent extracts of 300 southwestern U.S.A. plant species in 69 families were evaluated against four microorganisms in an agar-streak bioassay. The dichloromethane extract of Guardiola platyphylla and ethanol extracts of Plumbago scandens, Acacia angustissima and Salvia sonomensis demonstrated the best spectrum of activity by completely inhibiting the growth of Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae and Candida albicans. Of the 300 species, 12 completely inhibited the growth of the gram-negative K. pneumoniae and 36 inhibited the yeast C. albicans. B. subtilis proved to be very susceptible with 188 species either completely inhibiting or slowing the growth of this gram-positive organism. S. aureus proved to be more selective with only 107 species affecting its growth. Ninety-one species demonstrated no inhibitory effects on any test organisms.

Biocrude production in arid lands

Abstract The structures of nine grindelic acid related diterpenes isolated as methyl esters from Grindelia camporum and Chrysothamnus paniculatus , were elucidated based on their spectral properties.

Antifungal eudesmanoids from Parthenium argentatum x P. tomentosa

Recent research in the development of bioenergy crops for arid and semiarid regions has stressed the objective of increasing biomass productivity in order to improve energetic and economic returns. However, an examination of the constraints on arid-adapted plant species indicates that a preferable approach to biocrude feedstock development is one that emphasizes quality, rather than quantity, of biomass. This conclusion is illustrated by economic and energetic comparisons of 4 potential biocrude feedstocks. The species with the greatest economic potential are those with high biocrude contents and moderate or low annual yields.

Grindelia camporum: Potential cash crop for the arid southwest

Abstract Investigation of guayule resin for antifungal activity has led to the isolation and characterization of six eudesmane-type sesquiterpenoids, five of which are new: 2-methoxy-eudesma-1,4,6-trien-3-one (argentone); 2-methoxy-15-nor-eudesma-1,4,6-trien-3-one (15-nor-argentone); 2-methoxy-15-hydroxy-eudesma-1,4,6-trien-3-one (15-hydroxy-argentone); 2-methoxy-eudesma-1,4,6-trien-3,8-dione (8-oxo-argentone); 2-methoxy-15-nor-eudesma-1,4,6-trien-3,8-dione (8-oxo-15-nor-argentone); and the previously identified 11-hydroxy-eudesma-4-en-3-one (carissone). Their structures were elucidated by one- and two-dimensional NMR spectroscopy and mass spectrometry. After 6 weeks all inhibited the growth of Aspergillus fumigatus (ATCC-13073) at 1.0 mg ml− 1 and complete inhibition of A. niger (UA-172-1) for 2-methoxy-eudesma-1,4,6-trien-3-one and 2-methoxy-15-nor-eudesma-1,4,6-trien-3-one. At 0.25 mg ml− 1 2-methoxy-eudesma-1,4,6-trien-3-one demonstrated 100% control against A. fumigatus and 80% control against A. niger.

16-hydroxycarnosic acid, a diterpene from Salvia apiana

Grindelia camporum is a conspicuously resinous, herbaceous perennial found in the Central Valley area of California. The resin is produced in multicellular glands, which occur on the surfaces of stems, leaves, and involucres. The resin is composed of grindelic acid and several of its derivatives. These labdane diterpenes are similar to the resin acids that constitute rosin, a principal product of the naval stores industry, and it seems likely that resin extracted from Grindelia would have uses similar to those of rosin. If improved varieties of Grindelia camporum can be developed that yield a higher proportion of resin, this species would be suitable for domestication as a new crop for arid lands.

Cardenolides and a lignan from Asclepias subulata

Abstract A dichloromethane extract of the leaves of Salvia apiana gave a new abietane, 16-hydroxycarnosic acid, and the known diterpene carsonic acid or salvin.

Diterpenoids of Conyza coulteri

Abstract Four new glycosides (three cardenolides and a lignan), nine previously reported cardenolide glycosides and a known triterpenoid were isolated from the ethyl acetate extract of the aerial parts of Asclepias subulata . The elucidation of the structures and stereochemistry of the new glycosides has been accomplished using mainly 1 H and 13 C NMR and mass (EI and FAB) spectral data of their acetyl derivatives and comparison of these data with those of known glycosides from the same plant as well as from other plants. The new compounds were identified as 16α-hydroxycalactin, 3β-(β- D -glucopyranosyloxy)-19-car coroglaucigenin 3β- D -glucoside and 4-(β- D -glucopyranosyloxy)-larciresinol.