A comparison of antirrhinoside distribution in the organs of two related Plantaginaceae species with different reproductive strategies.

A study of two related plants (Antirrhinum majus L. and Linaria vulgaris Mill.) containing the same defensive compound (the iridoid glucoside, antirrhinoside) but with reproductive strategies that differ during ontogeny was undertaken. Young leaves are important to plants due to their higher photosynthetic rates and, therefore, should be better protected with higher concentrations of defensive compounds such as antirrhinoside. Declining concentrations of antirrhinoside as leaves aged was found for A. majus but this was generally not the case for L. vulgaris. Concentrations of antirrhinoside in root tissue were low and constant throughout ontogeny for A. majus whereas for L. vulgaris root levels of antirrhinoside were high during the period when vegetative growth is its sole means of reproduction. Antirrhinoside in L. vulgaris roots declined relative to A. majus roots during budding and flowering. During flowering, significantly less antirrhinoside and relative biomass are devoted to L. vulgaris flowers than in A. majus. While these findings are consistent with Optimal Defense Theory (ODT) further work on the distribution of antirrhinoside and the effect of insect herbivory on plant fitness in other related species is needed.

The iridoid glucoside, antirrhinoside, from Antirrhinum majus L. has differential effects on two generalist insect herbivores.

The iridoid glucoside, antirrhinoside, is constitutively distributed throughout Antirrhinum majus L. in a manner consistent with its possible role as an allelochemical, but there is no evidence that it has a defensive function with respect to insect herbivory. To address this question, two generalist herbivores, Lymantria dispar L. (gypsy moth) and Trichoplusia ni Hübner (cabbage looper) were chosen for feeding trials on excised whole leaves of A. majus and in artificial diet assays. In leaf excision feeding trials, fourth instar gypsy moth rejected, without sampling, the leaves of A. majus regardless of what node the leaf was excised from. In contrast, fourth instar cabbage looper readily fed on the excised leaves, and antirrhinoside was not found in their bodies or feces (frass) as determined by thin layer and high-pressure liquid chromatography. In the leaf and diet assays, a second major leaf iridoid in A. majus, antirrhide, was found in both cabbage looper and gypsy moth frass. In diet feeding assays, the growth of gypsy moth and cabbage looper were not inhibited by methanol extracts, iridoid fractions, or pure antirrhinoside at concentrations of 0.6% in diet, but cabbage looper growth was enhanced. At an antirrhinoside concentration of 3.3% in diet, gypsy moth growth was reduced, whereas cabbage looper growth again increased significantly relative to the control. It is likely that antirrhinoside functions as defense against herbivory for one generalist insect herbivore but also, at low concentrations, enhances the growth of another.

The distribution of two major Iridoids in different organs of Antirrhinum majus L. at selected stages of development.

Two iridoid glucosides isolated from leaves of Antirrhinum majus L. were identified as the known compounds antirrhinoside and antirrhide. Plants grown hydroponically demonstrated that antirrhinoside is present in all plant organs including the roots. In contrast, antirrhide is found only in leaves. Furthermore, both iridoids were identified in the main stem axillary leaves and leaves on the lateral branches. The highest concentrations of antirrhinoside were found in the main and lateral stems as well as the buds and flowers. As leaves age, for both cultivars, the levels of antirrhinoside drop significantly, and there is a corresponding increase in antirrhide. In spite of the different genetic backgrounds of the two cultivars, the overall distribution of the iridoids was similar during vegetative and flowering development. Radiolabeling of recently expanded axillary leaves with (14)CO(2) showed that both antirrhinoside and antirrhide were prominently labeled in the laminar tissue. However, only (14)C-antirrhinoside was recovered in the subtending petiole tissue, consistent with the suggestion that it is a phloem mobile compound.

Changes in polyphenols of the seed coat during the after-darkening process in pinto beans (Phaseolus vulgaris L.).

Proanthocyanidins and flavonoids were isolated and identified from seed coats of two aged and nonaged pinto bean lines: 1533-15 and CDC Pintium. The seed coat of 1533-15 darkens slowly and never darkens to the same extent as CDC Pintium. Analysis of the overall level of proanthocyanidins using a vanillin assay demonstrated that aged and nonaged seed coats of CDC Pintium had significantly higher levels of proanthocyanidins than aged and nonaged 1533-15 seed coats. Aged and nonaged seed coats of both lines were found to contain one main flavonol monomer, kaempferol, and three minor flavonols, kaempferol 3-O-glucoside, kaempferol 3-O-glucosylxylose, and kaempferol 3-O-acetylglucoside. These compounds were identified by NMR and ESI-MS analysis (except for kaempferol 3-O-acetylglucoside, which was tentatively identified only by ESI-MS analysis) and quantified using HPLC-DAD. The combined concentrations of all the kaempferol compounds in seed coats of CDC Pintium were significantly higher than in seed coats of 1533-15, and the combined contents did not change after aging. The content of kaempferol decreased nearly by half in the seed coats of CDC Pintium after aging, whereas no significant change was observed in the seed coats of 1533-15. Proanthocyanidin fractions from both lines, aged and nonaged, were subjected to LC-MS/MS analysis and found to be composed primarily of procyanidins. Procyanidins in the seed coats were predominantly polymers with the degree of polymers higher than 10. The proportion of these polymers decreased after aging, while that of the low-molecular-weight procyanidins increased. A catechin-kaempferol adduct was tentatively identified in both lines by LC-MS/MS, and the concentration increased in the seed coats after aging.

A flavanone and two phenolic acids from Chrysanthemum morifolium with phytotoxic and insect growth regulating activity.

Leaves of Chrysanthemum morifolium cv. Ramat were extracted sequentially with hexane, ethyl acetate, and methanol. The methanol fraction, when incorporated into artificial diet was found to reduce the growth of cabbage looper (Trichoplusia ni Hubner) larvae at concentrations between 500 and 5000 ppm of diet. Fractionation of the methanol extract on a Sephadex column yielded five fractions, three of which reduced the weight of larvae relative to the control. One fraction was analyzed using high performance liquid chromatography (HPLC) and found to contain three main constituents. These compounds were purified using a combination of gel permeation chromatography on Sephadex LH20 and HPLC, and analyzed by 1H and 13CNMR as well as undergoing chemical and physical analyses. The compounds were identified as: 1, chlorogenic acid (5-O-caffeoylquinic acid); 2, 3,5-O-dicaffeoylquinic acid; and 3, 3', 4',5-trihydroxyflavanone7-O-glucuronide (eriodictyol7-O-glucuronide). At concentrations between 100 to 1000 ppm these compounds reduced both growth and photosynthesis of Lemna gibba L. with the order of efficacy being: flavanone > chlorogenic acid > 3,5-O-dicaffeoylquinic acid. Furthermore, when incorporated separately into artificial diet these compounds, at 10 to 1000 ppm, enhanced or reduced growth of the cabbage looper (Trichoplusia ni) and gypsy moth (Lymantria dispar L.).

Antioxidant activity of extracts, condensed tannin fractions, and pure flavonoids from Phaseolus vulgaris L. seed coat color genotypes.

Twelve different seed coat color genotypes of Phaseolus vulgaris L. were extracted and pure flavonoids isolated from 10 of these. The seed coat methanol extracts, tannin fractions, and pure flavonoids all displayed antioxidant activity in a fluorescence-based liposome assay. The relatively high activity of the condensed tannin (proanthocyanidin) fractions indicates that these may play an important role in the overall activity of the extracts. This activity also indicates that although these polyphenols cause problems in digestibility, they may be important dietary supplements with beneficial health effects. The pure anthocyanins delphinidin 3-O-glucoside (1), petunidin 3-O-glucoside (2), and malvidin 3-O-glucoside (3) and the flavonol quercetin 3-O-glucoside (4) isolated from seed coats also had significantly higher antioxidant activity than the Fe(2+) control. The activity of kaempferol 3-O-glucoside (5) was not different from that of the Fe(2+) control. These findings suggest that variously colored dry beans may be an important source of dietary antioxidants.