David G. Lynn

Relationship between trigonelline concentration and promotion of cell arrest in G2 in cultured roots of Pisum sativum

Abstract Trigonelline, G2 Factor, present in cotyledons of Pisum sativum is transported to roots and shoots after germination. This hormone promotes prefere

Induction of cell arrest in G2: structural specificity of trigonelline

Abstract Synthetic analogues of N -methyl nicotinic acid, trigonelline, were prepared to test the structural features necessary for the induction of cellular arrest in G2 in Pisum sativum . Analogues that (1) were regioisomers of trigonelline, (2) possessed different 1,3-substituents, and (3) contained additional substituents on the pyridine ring were tested for their ability to induce cell arrest in G2 and to antagonize trigonelline induced arrest in G2. Only N -methyi-3-quinoline-carboxylic acid and 1-methyl nicotinamide induced cell arrest in G2, and 1-methyl-4-pyridine carboxylic acid and 1-methyl-2-pyridine carboxylic acid were effective trigonelline antagonists. These data further support a specific role for trigonelline in the induction of cell arrest in G2.

Trigonelline, nicotinic acid and nicotinamide in seedlings of Pisum sativum

Abstract Levels of trigonelline, nicotinic acid and nicotinamide have been examined in pea plants from the ungerminated seed to 10 days of age. The total quantity of trigonelline ranged between 70 and 81 μg in seeds to 7-day-old plants. At 10 days, the quantity of trigonelline increased to 101 μg. During the first 10 days, the concentration of trigonelline decreased in all regions of the seedling. Quantities of nicotinic acid within the seedling fell immediately after germination from 11.4 to 4.4 μg at 3 days but increased to 18.3 μg at 10 days. Unlike the decreasing trigonelline concentrations, nicotinic acid concentration throughout the seedling appeared relatively stable. Quantities of nicotinamide were less than 1% that of trigonelline, and never reached 1 μg total. The only noticeable increase in the concentration of nicotinamide occurred in leaves of 10-day-old plants. When [14C]trigonelline was injected at the cotyledonary node, it was transported to all regions of the plant and the majority (65%) went to epicotyl tissues.

A versatile total synthesis of xenognosin

Abstract Xenognosin, 4 , the first identified host recognition substance for parasitic angiosperms has been synthesized by a route efficient for the preparation of several structural analogoues.

Nicotinic acid and nicotinamide metabolism and promotion of cell arrest in G2 in Pisum sativum

Abstract Nicotinic acid and nicotinamide are immediate precursors of trigonelline, a hormone present in cotyledons of Pisum sativum L. which promotes cell arrest in G2 during cell maturation in roots and shoots. All three compounds are members of the pyridine nucleotide pathway for the synthesis of NAD and NADP. Concentrations of nicotinic acid and nicotinamide in excised roots grown for 3 days in Whites medium with sucrose were determined by HPLC. Results suggest that nicotinamide is rapidly converted first to nicotinic acid and then trigonelline. High nicotinic acid concentrations may occur in excised roots. Conversion of trigonelline to nicotinic acid in excised roots did not occur in these experiments. The concentrations of either nicotinamide or nicotinic acid in roots are not related to the proportions of cells arrested in G2. Trigonelline promotes cell arrest in G2, and nicotinic acid and nicotinamide are active only because they are converted to trigonelline.

THE INDOLE ALKALOID, HYPAPHORINE AND PTEROCARPUS SEED PROTECTION

Abstract L -Hypaphorine has been isolated as a major constituent of the seeds of Pterocarpus officinalis , seeds which are rejected as a food source by a wide variety of seed-eating rodents dwelling in the same habitat. Incorporation of the isolated hypaphorine into artificial diets of a small seed predator, Liomys salvini (a rodent) supports its role as a feeding deterrent.

New cytotoxic principles from Datisca glomerata

Datisca glomerata has been systematically fractionated by following cellular toxicity in an effort to identify previously uncharacterized cytotoxic principles. Several new cucurbitacin glycosides, including datiscosides B(8), C(3), D(9), E(4), F(5), G(6), and H(10) and the known compound datiscoside (1), as well as cucurbitacins B(11), D(2), and F(7) have been isolated and characterized. Structures were assigned to the compounds on the basis of their high field 1H n.m.r., 13C n.m.r., high-resolution mass spectra (CI, EI, and FD) and chemical interconversions. The structure of datiscoside C(3) was independently established by single-crystal X-ray analysis at 193 and 293 K.

The chemistry of toxic principles from Maytenus nemerosa

Abstract Maytenus nemerosa has been fractionated systematically by following the toxicity of extracts, partitioned solutions and column chromatographic fractions against cultured KB cells. Several compounds were isolated in this fashion, including 3-oxo-20(29)-lupen-30-al, β-amyrin, 29-hydroxyfriedelan-3-one, 30-hydroxy-20(29)-lupen-3-one, 30-hydroxyfriedelan-3-one and lup-20(29)-ene-3β,30-diol, as well as tingenone, 20-hydroxytingenone and galactitol. 3-Oxo-20(29)-lupen-30-al was shown to be cytotoxic for the first time; the structural basis of this cytotoxicity was investigated, in part, by bioassay of four products obtained by chemical transformation of single, isolated principles.

Afromontoside. A new cytotoxic principle from Dracaena afromontana

A new cytotoxic principle, steroidal saponin afromontoside (1), has been isolated from a methanolic extract of the twigs of Dracaena afromontana. It was shown to be (25R)-furost-5-ene-3β,22α,26-triol 26-O-α-L-rhamnopyranoside 3-O-([O-α-L-rhamnopyranosyl(1→4)]-β-D-glucopyranoside) by spectral and chemical methods. The aglycone of afromontoside, diosgenin, as well as dihydrodiosgenin and several structurally related compounds have been shown to be cytotoxic to cultured KB cells.