Basil A. Burke

Polar epicuticular lipids of Lycopersicon pennellii

Abstract Trichome exudates of Lycopersicon pennellii yielded nine 2,3,4-tri-O-acylglucose esters as α- and β-anomers from the polar fraction of the epicuticular lipid mixture. The esters were primarily derived from 2-methylpropanoic, 2-methylbutanoic, 3-methylbutanoic, 8-methylnonanoic and n-decanoic acids, together with trace quantities of 10-methylundecanoic and n-dodecanoic acids.

Isolation, characterization and activity of phytotoxic compounds from quackgrass [Agropyron repens (L.)Beauv.]

Previous experiments showed that legumes grown in the presence of living or herbicidally treated quackgrass residues or extracts exhibited reduced seedling root and shoot growth and decreased nodulation and nitrogen fixation. Aqueous extracts of quackgrass shoots were most inhibitory to plant growth. Upon sequential partitioning of an aqueous extract of quackgrass shoots, the ether extract possessed the most activity and caused 50% reductions in radicle elongation of eight crop and weed species at concentrations of less than 240 μg/ml (small-seeded species) and 1000 μg/ml (large-seeded species). Snapbeans (Phaseolus vulgaris L. “Bush Blue Lake”) grown aseptically in agar containing an ether extract at 100 and 200 μg/ml exhibited severe root browning, lack of root hair formation, and a two- to three-fold reduction in root and shoot dry weights. The ether extract of quackgrass shoots had no inhibitory effect on the growth of fourRhizobium species in Petri dishes or two species in broth culture. Inhibitors present in the ether extract may influence the legumeRhizobium symbiosis indirectly by reducing legume root growth and root hair formation. The ether extract of quackgrass shoots was separated using high-pressure liquid, thin-layer, and liquid column chromatography in an attempt to isolate and identify the inhibitors responsible for the inhibition of seedling growth. Two closely related flavonoid inhibitors were isolated from the ether extract. One was identified as 5,7,4′-trihydroxy-3′,5′-dimethoxyflavone (tricin). Both flavonoids caused 50% inhibition of radicle elongation in cress (Lepidium sativum L. “Burpee curly”) seeds at concentrations of less than 125 μg/ml. Both flavonoids were found in ether extracts of quackgrass shoots and rhizomes, but the largest amounts of both compounds occurred in quackgrass shoots collected from the field.

Sesquiterpene lactones and a sesquiterpene diol from Jamaican Ambrosia peruviana

Abstract A new sesquiterpene diol and four pseudoguaianolides have been isolated from the aerial part of a Jamaican collection of Ambrosia peruviana . The structures have been identified as alloaromadendrane-4β, 10α-diol, psilostachyins C and B, ambrosin and damsin, respectively, by chemical and spectroscopic means.

A new fatty acid methyl ester and other biologically active compounds from Aspergillus niger

Abstract Methyl 3-methyl-8-hydroxy-4-decenoate, a new C10 fatty acid methyl ester, was isolated and characterized from Aspergillus niger var. Tieghem. The chemical synthesis of this compound has also been achieved. Other compounds characterized from A. niger were phenylethanol, phenylacetic acid, phenoxyacetic acid, p-methoxyphenylacetic acid, mannitol and citric acid. All compounds except mannitol, inhibited the germination of cress and lettuce seeds. Antifungal bioassay of the above compounds on Cladosporium herbarum showed activity except for the C10 fatty acid methyl ester, mannitol and citric acid.

Phytotoxins from Alternaria helianthi: radicinin, and the structures of deoxyradicinol and radianthin

Abstract A novel compound, radianthin, with phytotoxic activity was isolated from liquid cultures of Alternaria helianthi and identified as a pyrone related to radicinin. A second metabolite was identified as radicinin itself while deoxyradicinol is described for the first time as a natural product.

Ferulate esters of higher fatty alcohols and allelopathy inKalanchöe daigremontiana

Ferulate esters of normal C22–C30 alcohols were found in the root extract ofKalanchöe daigremontiana and the freen-C30 alcohol, triacontanol, was found on the leaves. Ferulic acid was isolated from the vermiculite in which plants were grown. Whole plant and tissue culture experiments were done to investigate the role of ferulic acid as an allelochemical and of triacontanol as a plant growth regulator inK. daigremontiana and other bioassay systems. No positive growth responses to triacontanol were observed, but inhibitation of growth response of plantlets by ferulic acid was seen.

Pyrenocine C, A phytotoxin-related metabolite produced by onion pink root fungus, Pyrenochaeta terrestris

Abstract The structure of pyrenocine C, a new metabolite isolated from onion pink root fungus, Pyrenochaeta terrestris (Hansen) has been elucidated as (±)-(2′E)-5-(1′-hydroxybut-2′-enyl)-4-methoxy-6-methyl-2-pyrone by spectroscopic methods and chemical correlation with pyrenocine A.

Phenyl propenoids from roots of Piper auritum

Abstract 1-propenal-3,4-(methylenedioxy)-5-methoxybenzene, 1-allyl-2,3-(methylenedioxy)-5-methoxybenzene, safrole and dillapiole have been isolated from the roots of Jamaican Piper auritum .

Studies on the mechanism of polyketide-derived biosynthesis of deoxyradicinin and related metabolites of Alternaria helianthi

The polyketide biosynthetic origin of deoxyradicinin, deoxyradicinol and 3-epideoxyradicinol has been demonstrated by incorporation studies with 13C-labelled precursors and 13C n.m.r. spectroscopy. The 13C n.m.r., 2H n.m.r., and mass spectra of deoxyradicinin isolated from fungal cultures grown in the presence of [2H3]sodium acetate indicated an uncommon condensation of two polyketide chains rather than a single hexaketide unit undergoing cyclization and ring-cleavage.