G.H.Neil Towers

Biological activities of lignans

Abstract Lignans are widely distributed in angiosperms and gymnosperms. The range of their structures and biological activities is broad. Various lignans are known to have anti-tumour, antimitotic and antiviral activity and to specifically inhibit certain enzymes. Toxicity to fungi, insects and vertebrates is observed for some lignans and a variety of physiological activities have been documented. This review summarizes what is presently known about the biological activities of lignans.

Biological activity of limonoids from the rutales

Abstract Limonoids are the most distinctive secondary metabolites of the plant order Rutales. Recent work has established a wide range of biological activities for these compounds, including insect antifeedant and growth regulating properties, a variety of medicinal effects in animals and humans, and antifungal, bacteriocidal, and antiviral activity. This review summarizes the literature on the biological activities of limonoids of known structure, and attempts to relate those activities to current concepts of the evolution of the limonoids.

Antitumor sterols from the mycelia of Cordyceps sinensis

Activity guided fractionations led to the isolation of two antitumor compounds 5 alpha,8 alpha-epidioxy-24(R)-methylcholesta-6,22-dien-3 beta-D-glucopyranoside and 5,6-epoxy-24(R)-methylcholesta-7,22-dien-3 beta-ol from the methanol extract of Cordyceps sinensis. Two previously known compounds, ergosteryl-3-O-beta-D-glucopyranoside and 22-dihydroergosteryl-3-O-beta-D-glucopyranoside were also isolated. The structures of hitherto unknown sterols were established by 1D and 2D NMR spectroscopic techniques with the former synthesized in order to confirm the identity of the sugar moiety by chemical correlation. The glycosylated form of ergosterol peroxide was found to be a greater inhibitor to the proliferation of K562, Jurkat, WM-1341, HL-60 and RPMI-8226 tumor cell lines by 10 to 40% at 10 micrograms/ml than its previously identified aglycone, 5 alpha,8 alpha-epidioxy-24(R)-methylcholesta-6,22-dien-3 beta-ol.

Ultraviolet-mediated antibiotic activity of thiophene compounds of Tagetes

Abstract Two intensely mauve UV fluorescent compounds isolated from Tagetes root were found to be phototoxic to Candida albicans . By chromatography on alumina followed by gel filtration on Sephadex LH-20, the compounds were identified as 5-(3-buten-1-ynyl)-2,2′-bithienyl and α-terthienyl.

Insecticidal 1H-cyclopentatetrahydro[b]benzofurans from Aglaia odorata

Abstract Bioassay-directed separation of a methanolic extract of the leaves of Aglaia odorata led to the isolation of a known cyclopentatetrahydrobenzofuran, rocaglamide, along with its congeners, desmethylrocaglamide, methyl rocaglate and rocaglaol. The structures of the three new compounds were determined on the basis of spectroscopic evidence and by comparisons of their 1H NMR data with those of rocaglamide. Rocaglamide and methyl rocaglate exhibited potent insecticidal activity both through growth inhibition and contact toxicity to the variegated cutworm, Peridroma saucia.

Nitrogen recycling in phenylpropanoid metabolism

Abstract Approximately 30–45% of plant organic matter is derived from l -phenylalanine, and to a lesser extent from l -tyrosine, through the cinnamate pathway. In the initial step, mediated by phenylalanine ammonia lyase, cinnamic acid and an equimolar amount of ammonium ion is generated. To determine the metabolic fate of the ammonia formed, [ 15 N]- l -phenylalanine was administered to potato discs in the light under aseptic conditions. It was found, using 15 N NMR spectroscopic analyses, that this nitrogen is first incorporated into the amide nitrogen of glutamine and then into glutamate. When incubations were repeated in the presence of methionine- S -sulphoximine, a known inhibitor of glutamine synthetase, only resonances corresponding to 15 NH 4 + and [ 15 N]- l -Phe accumulated. It is proposed that during active phenylpropanoid metabolism, the ammonia released by phenylalanine ammonia lyase/tyrosine ammonia lyase is efficiently recycled back to Phe/Tyr with glutamate serving as aminoreceptor and donor. This is the first evidence for a novel nitrogen cycle in plants.

Leaf-swallowing by chimpanzees: A behavioral adaptation for the control of strongyle nematode infections

Swallowing whole leaves by chimpanzees and other African apes has been hypothesized to have an antiparasitic or medicinal function, but detailed studies demonstrating this were lacking. We correlate for the first time quantifiable measures of the health of chimpanzees with observations of leaf-swallowing in Mahale Mountains National Park, Tanzania. We obtained a total of 27 cases involving the use ofAspilia mossambicensis (63%),Lippia plicata (7%),Hibiscus sp. (15%),Trema orientalis (4%), andAneilema aequinoctiale (11%), 15 cases by direct observation of 12 individuals of the Mahale M group. At the time of use, we noted behavioral symptoms of illness in the 8 closely observed cases, and detected single or multiple parasitic infections (Strongyloides fulleborni, Trichuris trichiura, Oesophagostomum stephanostomum) in 10 of the 12 individuals. There is a significant relationship between the presence of whole leaves (range, 1–51) and worms of adultO. stephanostomum (range, 2–21) in the dung. HPLC analysis of leaf samples collected after use showed that thiarubrine A, a compound proposed to act as a potent nematocide in swallowingAspilia spp., was not present in leaves ofA. mossambicensis or the three other species analyzed. Alternative nematocidal or egg-laying inhibition activity was not evident. Worms ofO. stephanostomum were recovered live and motile from chimpanzee dung, trapped within the folded leaves and attached to leaf surfaces by trichomes, though some were moving freely within the fecal matter, suggesting that the physical properties of leaves may contribute to the expulsion of parasites. We review previous hypotheses concerning leaf-swallowing and propose an alternative hypothesis based on physical action.

Allelopathic properties of α-terthienyl and phenylheptatriyne, naturally occurring compounds from species of asteraceae

Alpha-terthienyl (α-T), a naturally occurring polyacetylene derivative from roots ofTagetes erecta L., and phenylheptatriyne (PHT), from leaves ofBidens pilosa L., were tested as possible allelopathic agents against four seedling species (Asclepias syriaca L.,Chenopodium album L.,Phleum pratense L.,Trifolium pratense L.).Asclepias was the most sensitive of the species. Allelopathic activity was enhanced in the presence of sunlight or sources of near-UV, with LC50s forA. syriaca of 0.15 ppm and 0.66 ppm with α-T and PHT, respectively; 0.27 and 0.85 forC. album; 0.79 and 1.43 forP. pratense, and 1.93 and 1.82 forT. pratense. Near-UV exposure was saturating but never more than found in summer sunlight at Ottawa, Canada. Growth inhibition was observed with seedlings treated with α-T and PHT but without near-UV irradiation. Germination of seedlings was also sensitive to α-T and PHT with or without near-UV treatment. α-T was extracted from soil surrounding the roots ofTagetes. Concentrations calculated for the soil (0.4 ppm) indicate that seedling growth could be significantly hindered. The activity and specificity of α-T was sufficiently high to warrant future field trials to assess its potential as a natural weed-control agent.

Conversion of p-coumaric acid to p-hydroxybenzoic acid by cell free extracts of potato tubers and Polyporus hispidus

Abstract The conversion of p -coumaric acid to p -hydroxybenzoic acid was demonstrated in vitro in both potato tuber and P. hispidus . The mechanism of the enzyme system is non-oxidative. This is the first report of a cell free system which is capable of converting a C 6 -C 3 acid to the corresponding C 6 -C 1 derivative from a fungus.

Rocaglamide, a natural benzofuran insecticide from Aglaia odorata

Abstract Rocaglamide, a highly substituted benzofuran, was isolated and identified as the active insecticidal constituent in the twigs of the Chinese rice flower bush, Aglaia odorata. This compound inhibits larval growth and is insecticidal to both variegated cutworms, Peridroma saucia and Asian armyworms, Spodoptera litura. LD50 values for fourth-instar P. saucia larvae were found to be 0.32 μg larvae−1 topically and 0.34 μg larvae−1 orally. Dammarane triterpenes and aminopyrrolidine bis-amides such as odorinol isolated from A. odorata were inactive against P. saucia.