Saponins show high entomotoxicity by cell membrane permeation in Lepidoptera

BACKGROUND: In this study, the effects of three saponins and one sapogenin with a triterpenoid or steroid structure in two lepidopteran insect cell lines, ovarian Bm5 and midgut CF‐203 cells, were analysed with regard to cell viability, cell membrane permeation, EcR responsiveness and DNA fragmentation. In addition, the entomotoxic action of Q. saponaria saponin with primary midgut cell cultures and larval stages of the cotton leafworm Spodoptera littoralis was tested. RESULTS: Both lepidopteran cell lines show a high sensitivity to all four sapo(ge)nins, with a concentration‐dependent viability loss and EC₅₀ values of 25–100 µM in MTT bioassays. A trypan blue assay with Q. saponaria saponin confirmed rapid cell membrane permeation to be a cause of cytotoxicity. Saponins caused no EcR activation in Bm5 cells, but a loss of ecdysteroid signalling was observed with IC₅₀ values of 5–10 µM . Lower saponin concentrations induced DNA fragmentation, confirming their potential to induce apoptosis. Finally, Q. saponaria saponin caused cytotoxicity in primary midgut cell cultures of S. littoralis (EC₅₀ = 4.7 µM ) and killed 70–84% of S. littoralis larvae at pupation at 30‐70 mg g^?1, while lower concentrations retarded larval weight gain and development. CONCLUSIONS: The data obtained provide evidence that saponins exert a strong activity on lepidopteran cells, presumably based on a cytotoxic action due to permeation of the cell membrane. Primary midgut cell cultures and larvae of S. littoralis showed high sensitivity to Q. saponaria saponin, indicating the insect midgut as a primary target for entomotoxicity and the potential use of saponins in the control of pest Lepidoptera. Copyright © 2012 Society of Chemical Industry     

Triterpene saponins of Quillaja saponaria show strong aphicidal and deterrent activity against the pea aphid Acyrthosiphon pisum

BACKGROUND: Saponins are a class of secondary plant metabolites consisting of a sugar moiety glycosidically linked to a hydrophobic aglycone (sapogenin) that often possess insecticidal activities. Four saponins were selected: two triterpene saponins, Q. saponaria saponins and aescin, and two steroidal saponins, digitonin and diosgenin. Their effects were investigated on an important pest species and a model piercing‐sucking insect, the pea aphid Acyrthosiphon pisum. The triterpene Q. saponaria saponins bark saponin received special attention because of its high activity. Aphids were challenged by oral and contact exposure to demonstrate aphicidal activities, and in choice experiments to support use as a natural deterrent. RESULTS: When aphids were exposed to supplemented artificial diet for 3 days, a strong aphicidal activity was recorded for three of the four saponins, with an LC₅₀ of 0.55 mg mL^?1 for Q. saponaria saponins, 0.62 mg mL^?1 for aescin and 0.45 mg mL^?1 for digitonin. The LT₅₀ values ranged between 1 and 4 days, depending on the dose. For diosgenin, only low toxicity (14%) was scored for concentrations up to 5 mg mL^?1. In choice experiments with treated diet, a deterrence index of 0.97 was scored for Q. saponaria saponins at 1 mg mL^?1. In contrast, direct contact showed no repellent effect. Spraying of faba bean plants with Q. saponaria saponins resulted in an LC₅₀ of 8.2 mg mL^?1. Finally, histological analysis in aphids fed with Q. saponaria saponins demonstrated strong aberrations of the aphid gut epithelium, and exposure of midgut CF‐203 cell lines to Q. saponaria saponins in vitro confirmed the cytotoxic effect. CONCLUSIONS: The present insect experiments provide strong evidence that saponins, as tested here with triterpene Q. saponaria saponins, can be useful as natural aphicides and deterrents. Furthermore, the insect midgut epithelium is suggested to be a primary target of saponin activity.Copyright © 2011 Society of Chemical Industry     

Insect growth inhibition,antifeedant and antifungal activity of compounds isolated/derived from Zingiber officinale Roscoe (ginger) rhizomes

Fresh rhizomes of Zingiber officinale (ginger), when subjected to steam distillation, yielded ginger oil in which curcumene was found to be the major constituent. The thermally labile zingiberene‐rich fraction was obtained from its diethyl ether extract. Column chromatography of ginger oleoresin furnished a fraction from which [6]‐gingerol was obtained by preparative TLC. Naturally occurring [6]‐dehydroshogaol was synthesised following condensation of dehydrozingerone with hexanal, whereas zingerone and 3‐hydroxy‐1‐(4‐hydroxy‐3‐methoxyphenyl)butane were obtained by hydrogenation of dehydrozingerone with 10% Pd/C. The structures of the compounds were established by ¹H NMR, ¹³C NMR and mass (EI‐MS and ES‐MS) spectral analysis. The test compounds exhibited moderate insect growth regulatory (IGR) and antifeedant activity against Spilosoma obliqua, and significant antifungal activity against Rhizoctonia solani. Among the various compounds, [6]‐dehydroshogaol exhibited maximum IGR activity (EC₅₀ 3.55 mg ml ^?1) while dehydrozingerone imparted maximum antifungal activity (EC₅₀ 86.49 mg litre^?1). © 2001 Society of Chemical Industry     

Evaluation of nematicidal properties of saponins from <Emphasis Type="Italic">Medicago</Emphasis> spp.

The nematicidal activity of saponins from Medicago arborea (tops), M. arabica (tops and roots) and M. sativa (tops and roots) against the plant-parasitic nematode Xiphinema index was investigated. Nematicidal activity of related prosapogenins and sapogenins on X. index is also described. Saponins from Medicago spp. at different concentrations were all nematicidal, those from M. arborea tops being the less effective. In general, saponins induced 100% mortality at 500 μg ml⁻¹ between 8 and 48 h, while prosapogenins resulted in toxicity starting at 125 μg ml⁻¹. Differences in the effects on X. index induced by prosapogenins and sapogenins were less pronounced, although prosapogenins displayed a larger range of activity. Assays with purified sapogenins demonstrated the relationship of the observed nematicidal activity of M. sativa and M. arborea to the content of the main aglycones (medicagenic acid and hederagenin, respectively) in the saponin extracts. Hederagenin displayed the highest bioactivity, giving 38% mortality after 1 h at 125 μg ml⁻¹.     

Synthesis and insecticidal activity of new pyrethroids

BACKGROUND: Pyrethroids are among the most potent pesticides known, with great potential for structural variation with retention or enhancement of potency. The simple methyl ester is easier to prepare (at least one step shorter) than the more complex pyrethroids modified on the alcohol moiety. The objective was to synthesise methyl esters of pyrethroid acids containing an aromatic ring on the acid moiety and evaluate their biological activity against Ascia monuste orseis Latr., Tuta absoluta Meyrick, Periplaneta americana (L.), Musca domestica L. and Sitophilus zeamais (Motsch.). RESULTS: The synthetic sequence required seven steps: protection of the hydroxyl groups of D ‐mannitol, diol oxidative cleavage with sodium metaperiodate, alkene formation by Wittig reaction with methoxycarbonylmethylidene(triphenyl)phosphorane, cyclopropanation, acetal hydrolysis with perchloric acid and oxidative cleavage with sodium metaperiodate gave methyl (1S, 3S)‐3‐formyl‐2,2‐dimethylcyclopropane‐1‐carboxylate. The final step comprised reaction of the aldehyde with five different aromatic phosphorus ylides to give the pyrethroids. CONCLUSION: An efficient and versatile synthesis of ten new pyrethroid methyl esters has been accomplished from the readily available D ‐mannitol in seven steps. All compounds showed insecticidal activity, and methyl (1S, 3S)‐3‐[(Z)‐2‐(4‐chlorophenyl)vinyl]‐2,2‐dimethylcyclopropane‐1‐carboxylate was the most active, killing 90% of A. monuste orseis and 100% of T. absoluta and P. americana. Copyright © 2009 Society of Chemical Industry     

In vivo control and in vitro antifungal activity of rhamnolipid B,a glycolipid antibiotic,against Phytophthora capsici and Colletotrichum orbiculare

The glycolipid antibiotic rhamnolipid B isolated from Pseudomonas aeruginosa strain B5 was evaluated for in vitro antifungal activity and in vivo control against phytophthora blight and anthracnose under glasshouse conditions. Rhamnolipid B showed antifungal activity against Cercospora kikuchii, Cladosporium cucumerinum, Colletotrichum orbiculare, Cylindrocarpon destructans, Magnaporthe grisea and Phytophthora capsici. Microscopic observation revealed that the high level of antifungal activity (10 µg ml ⁻¹) against P capsici was mainly due to a lytic effect on zoospores. Zoospore lysis began in the presence of 10 µg ml ⁻¹ of rhamnolipid B and most of the zoospores were collapsed at 25 µg ml ⁻¹. Rhamnolipid B showed inhibitory activity against the germination of zoospores and hyphal growth of P capsici at concentrations of 50 µg ml ⁻¹. Spore germination of the anthracnose plant pathogen C orbiculare was also inhibited in the presence of 50 µg ml ⁻¹ of rhamnolipid B, although hyphal growth was not affected at this concentration. In the glasshouse, the efficacy of rhamnolipid B against phytophthora blight was similar to that of metalaxyl on pepper plants when treated just before inoculation with P capsici. Treatment with either at 500 µg ml ⁻¹ completely protected pepper plants from phytophthora blight. Rhamnolipid B also suppressed the development of C orbiculare infection on leaves of cucumber plants. © 2000 Society of Chemical Industry     

Acaricidal activity of triketone analogues derived from Leptospermum scoparium oil against house‐dust and stored‐food mites

BACKGROUND: Various attempts to control the populations of house‐dust and stored‐food mites have been implemented using synthetic chemicals. Although effective, the repeated use of these chemicals has led to resistance owing to the mite's high reproductive potential and short life cycle. Therefore, this study aimed to develop natural acaricides using oils derived from Leptospermum scoparium JR & G Forst., which may affect the overall biological activity of a mite without adverse effects. Results were compared with those from using benzyl benzoate and N,N‐diethyl‐3‐methylbenzamide (DEET). RESULTS: The LD₅₀ values of L. scoparium oil were 0.54, 0.67 and 1.12 µg cm^?2 against Dermatophagoides farinae (Hughes), D. pteronyssinus (Troussart) and Tyrophagus putrescentiae (Schrank) respectively. The active constituent isolated from L. scoparium was identified as leptospermone (6‐isovaleryl‐2,2,4,4‐tetramethyl‐1,3,5‐cyclohexanetrione) by spectroscopic analysis. Based on the LD₅₀ values of leptospermone and its derivatives, the most toxic compound against D. farinae was leptospermone (0.07 µg cm^?2), followed by 2,2,4,4,6,6‐hexamethyl‐1,3,5‐cyclohexanetrione (1.21 µg cm^?2), benzyl benzoate (10.03 µg cm^?2) and DEET (37.12 µg cm^?2). Furthermore, similar results were observed when the leptospermone and its derivatives were tested against D. pteronyssinus and T. putrescentiae. CONCLUSIONS: These results indicate that L. scoparium oil‐derived materials, particularly leptospermone and 2,2,4,4,6,6‐hexamethyl‐1,3,5‐cyclohexanetrione, have potential for development as new agents for the control of three species of mite. Copyright © 2008 Society of Chemical Industry     

Acaricidal activities of the active component of Lycopus lucidus oil and its derivatives against house dust and stored food mites (Arachnida: Acari)

BACKGROUND: Recent studies have focused on materials derived from plant extracts as mite control products against house dust and stored food mites because repeated use of synthetic acaricides had led to resistance and unwanted activities on non‐target organisms. The aim of this study was to evaluate the acaricidal activity of materials derived from Lycopus lucidus against Dermatophagoides farinae, D. pteronyssinus and Tyrophagus putrescentiae. RESULTS: The LD₅₀ values of L. lucidus oil were 2.19, 2.25 and 8.45 µg cm^?2 against D. farinae, D. pteronyssinus and T. putrescentiae. The acaricidal constituent of L. lucidus was isolated by chromatographic techniques and identified as 1‐octen‐3‐ol. In a fumigant method against D. farinae, the acaricidal activity of 1‐octen‐3‐ol (0.25 µg cm^?2) was more toxic than N,N‐diethyl‐m‐toluamide (DEET) (36.84 µg cm^?2), followed by 3,7‐dimethyl‐1‐octen‐3‐ol (0.29 µg cm^?2), 1‐octen‐3‐yl butyrate (2.32 µg cm^?2), 1‐octen‐3‐yl acetate (2.42 µg cm^?2), 3,7‐dimethyl‐1‐octene (9.34 µg cm^?2) and benzyl benzoate (10.02 µg cm^?2). In a filter paper bioassay against D. farinae, 1‐octen‐3‐ol (0.63 µg cm^?2) was more effective than DEET (20.64 µg cm^?2), followed by 3,7‐dimethyl‐1‐octen‐3‐ol (1.09 µg cm^?2). CONCLUSION: 1‐Octen‐3‐ol and 3,7‐dimethyl‐1‐octen‐3‐ol could be useful as natural agents for the management of three mite species. Copyright © 2011 Society of Chemical Industry     

Synthesis and fungicidal activity of tubulin polymerisation promoters. Part 1: pyrido[2,3‐b]pyrazines

BACKGROUND: The excellent fungicidal activity of [1,2,4]triazolo[1,5‐a]pyrimidines suggested the search for further analogues with improved properties. RESULTS: A series of novel trisubstituted pyrido[2,3‐b]pyrazines has been designed and prepared as 6,6‐biheterocyclic analogues of related 5,6‐bicyclic [1,2,4]triazolo[1,5‐a]pyrimidines. Their fungicidal activity was evaluated against the plant pathogens Puccinia recondita Rob. ex Desm. f. sp. tritici (Eriks.) CO Johnston (wheat brown rust), Mycosphaerella graminicola (Fuckel) Schroter (Septoria tritici Rob., leaf spot of wheat) and Magnaporthe grisea (Hebert) Barr (Pyricularia oryzae Cav., rice blast). Structure–activity relationship studies revealed the advantage of a fluoro substituent in position 6 and of a secondary amine in position 8. CONCLUSION: 8‐Amino‐7‐aryl‐6‐halogen‐substituted pyrido[2,3‐b]pyrazines have been prepared as 6,6‐biheterocyclic analogues of similarly substituted triazolopyrimidine fungicides. A concise four‐step synthesis route has been worked out to prepare these novel compounds from commercially available starting materials. [(R)‐(1,2‐Dimethylpropyl)]‐[6‐fluoro‐7‐(2,4,6‐trifluorophenyl)pyrido[2,3‐b]pyrazin‐8‐yl]amine showed excellent activity against three economically important phytopathogens. Copyright © 2009 Society of Chemical Industry     

Yucca schidigera extract: a potential biofungicide against seedborne pathogens of sorghum

Treatment of seeds with an aqueous extract of yucca (YE), Yucca schidigera, was evaluated for antifungal activity against seedborne pathogens as well as its effect on seed germination and seedling growth of sorghum (Sorghum bicolor). The antifungal effect of YE was observed against Leptosphaeria sacchari (syn. Phoma sorghina) when the extract was applied at 2·5 and 10% concentrations. At 10% concentration, YE significantly reduced not only the incidence of L. sacchari, but also that of Fusarium spp., Cochliobolus lunatus (syn. Curvularia lunata) and Cladosporium spp. The effect of 10% YE on seedborne fungi was broader than the fungicide fludioxonil, particularly with regard to Fusarium. Furthermore, the number of normal, healthy‐looking seedlings increased in a dose‐responsive manner with YE treatment. Seedling vigour was also stimulated by YE but no correlation was observed with the concentrations tested. Under glasshouse conditions, the treatment of seeds with 10% YE increased the emergence of seedlings and plant height and reduced the number of seedlings with crown rot compared to negative controls and saponin. The positive effect was similar to the effect obtained with fungicide‐treated seeds. Treatment of seeds with synthetic saponin inhibited seedborne fungi less effectively and also negatively affected germination and vigour of the seedlings, compared to the treatment with YE. The results demonstrate an agronomic potential for the use of YE as a biofungicide for seed treatment of sorghum. The difference between the antifungal and the vigour‐stimulating effects of YE warrants further investigation.     

Design,synthesis and structure–activity relationships of novel ALS inhibitors

The paper describes the biophore models of sulfonylurea, imidazolinone, triazolopyrimidinesulfonamide and 5‐pyrimidyltriazolo‐3‐sulfonamides established by the Apex‐3D method. A series of N‐phenylsulfonyl‐N ′‐(thiadiazol‐2‐yl)oxamides and three types of triazolopyrimidinesulfonamide were synthesised and their herbicidal activities determined to assess the validity of the model. In general, the model gave useful leads to activity, although the actual level was not always predicted accurately. In only a few cases did compounds predicted as being active prove to be inactive in the bioassay, and compounds with little or no activity were clearly indicated. As a result of this work, the compound N,N ′‐[1‐(5,7‐dimethyl‐1,2,4‐triazolo[1,5‐a]pyrimidin‐2‐yl‐thio)butane‐2,3‐di‐imino]bis(2‐chlorobenzenesulfonamide) was selected as showing good activity against a range of species, and will be used as a lead for further development. © 2000 Society of Chemical Industry     

Emamectin benzoate as a candidate for a trunk‐injection agent against the pine wood nematode,Bursaphelenchus xylophilus

In order to develop an effective trunk‐injection agent against pine wood nematode, Bursaphelenchus xylophilus, an in vitro assay was used to examine the antinematodal activity of 58 commercially available compounds with known modes of action. Among compounds tested, the GABA receptor agonists had better anti‐nematodal activity than compounds influencing glutamate, N‐methyl‐D ‐aspartate, β‐adrenergic, dopamine, muscarinic acetylcholine and nicotinic acetylcholine receptors, as well as those inhibiting acetylcholinesterase, monoamine oxidase, 5‐hydroxytryptamine uptake and Ca²⁺, K⁺, Na⁺ and Cl⁻ channels. Avermectins and milbemycins strongly inhibited propagation of the nematode. Emamectin benzoate proved to be the most active (IC₉₅ 0.050 µM ) being over 140 times more active than the active ingredient of conventional trunk‐injection agents. It is concluded that emamectin benzoate is a strong candidate for an anti‐nematodal trunk injection agent. © 2000 Society of Chemical Industry     

Metabolism of the herbicide glufosinate‐ammonium in plant cell cultures of transgenic (rhizomania‐resistant) and non‐transgenic sugarbeet (Beta vulgaris), carrot (Daucus carota), purple foxglove (Digitalis purpurea) and thorn apple (Datura stramonium)

The metabolism of the herbicide glufosinate‐ammonium was investigated in heterotrophic cell suspension and callus cultures of transgenic (bar‐gene) and non‐transgenic sugarbeet (Beta vulgaris). Similar studies were performed with suspensions of carrot (Daucus carota), purple foxglove (Digitalis purpurea) and thorn apple (Datura stramonium). ¹⁴C‐labelled chemicals were the (racemic) glufosinate, L ‐glufosinate, and D ‐glufosinate, as well as the metabolites N‐acetyl L ‐glufosinate and 3‐(hydroxymethylphosphinyl)propionic acid (MPP). Cellular absorption was generally low, but depended noticeably on plant species, substance and enantiomer. Portions of non‐extractable residues ranged from 0.1% to 1.2% of applied ¹⁴C. Amounts of soluble metabolites resulting from glufosinate or L ‐glufosinate were between 0.0% and 26.7% of absorbed ¹⁴C in non‐transgenic cultures and 28.2% and 59.9% in transgenic sugarbeet. D ‐Glufosinate, MPP and N‐acetyl L ‐glufosinate proved to be stable. The main metabolite in transgenic sugarbeet was N‐acetyl L ‐glufosinate, besides traces of MPP and 4‐(hydroxymethylphosphinyl)butanoic acid (MPB). In non‐transgenic sugarbeet, glufosinate was transformed to a limited extent to MPP and trace amounts of MPB. In carrot, D stramonium and D purpurea, MPP was also the main product; MPB was identified as a further trace metabolite in D stramonium and D purpurea. © 2001 Society of Chemical Industry     

Synthesis, characterization, absolute structural determination and antifungal activity of a new chlorinated aromatic avenaciolide analogue

BACKGROUND: Avenaciolide, a natural product isolated from Aspergillus avenaceus H. Smith, possesses several interesting biological properties, such as antifungal and antibacterial activities and inhibition of glutamate transport in mitochondria. In a study aiming to discover new compounds with antifungal activity, a bis‐γ‐lactone analogous to avenaciolide was prepared and characterized by elemental analysis, mass spectrometry, and infrared and NMR spectroscopy. RESULTS: The absolute structures of this compound and of the synthetic precursor (also a bis‐γ‐lactone) were determined by X‐ray diffraction analysis. The bis‐γ‐lactones synthesized crystallize in the orthorhombic space group P2₁2₁2₁, and the crystal packings are supported by C? H···O hydrogen bonds. The compound showed antifungal activity against Colletotrichum gloeosporioides (Penz.) Penz. & Sacc., while the synthetic precursor was inactive under the in vitro test conditions employed. CONCLUSION: The results indicate that it is not only the bis‐γ‐lactone skeleton that is important to antifungal activity. The latter also depends on the presence of the exocyclic double bond possibly due to a Michael addition type reaction with the fungal enzymes. Copyright © 2008 Society of Chemical Industry     

Acaricidal properties of piperazine and its derivatives against house‐dust and stored‐food mites

BACKGROUND: Piperazine derivatives possess pharmacological properties, yet the acaricidal activity of these compounds has not been investigated. This study was conducted to evaluate the colour alteration and acaricidal activity of piperazine derivatives against Dermatophagoides spp. and Tyrophagus putrescentiae (Schrank) using filter paper and fumigant methods. RESULTS: In a fumigant bioassay, 1‐phenylpiperazine (7.83 µg cm^?2) against D. farinae (Hughes) was found to be 4.7 times more toxic than DEET (36.84 µg cm^?2), followed by benzyl benzoate (9.72 µg cm^?2), piperazine (11.41 µg cm^?2), 1‐ethoxycarbonylpiperazine (20.14 µg cm^?2) and 1‐(2‐methoxyphenyl)piperazine (22.14 µg cm^?2). In a filter paper bioassay, 1‐(2‐methoxyphenyl)piperazine (3.65 µg cm^?2) was 5.7 times more toxic than DEET (20.64 µg cm^?2), followed by 1‐ethoxycarbonylpiperazine (4.02 µg cm^?2), 1‐phenylpiperazine (4.75 µg cm^?2), benzyl benzoate (7.83 µg cm^?2) and piperazine (10.59 µg cm^?2). Similar results have been exhibited with piperazine derivatives against D. pteronyssinus (Troussart). However, no activity against T. putrescentiae was observed for piperazine derivatives, except for piperazine. CONCLUSIONS: These results indicate that piperazine derivatives may be suitable as vapour‐phase acaricide fumigants owing to their high volatility, acaricidal activity and safety. 1‐Phenylpiperazine was found to be an excellent mite indicator based on the colour change it induced. Taken together, these findings indicate that piperazine derivatives may be used to replace existing problematical acaricides owing to their activity and ability to act as a mite indicator. Copyright © 2009 Society of Chemical Industry     

Phytoanticipins from banana (<Emphasis Type="Italic">Musa acuminata</Emphasis> cv. Grande Naine) plants,with antifungal activity against <Emphasis Type="Italic">Mycosphaerella fijiensis</Emphasis>, the causal agent of black Sigatoka

The previously detected antifungal activity against Mycosphaerella fijiensis of aqueous infusions of healthy banana (Musa acuminata cv. Grande Naine) leaves, suggested the production of phytoprotectants by the plant. The bioassay-guided VLC-purification of the lyophilized infusion of the leaves of 4-month old healthy banana (M. acuminata cv. Grande Naine) plants, resulted in the purification of a phytoanticipin with strong antifungal activity against M. fijiensis Morelet, the causal agent of black Sigatoka, the most destructive and devastating disease of bananas and plantains in the world. The LC-MS analysis of the purified phytoanticipin suggests a steroidal saponin structure with four sugar units attached to the C-3 position of a diosgenin-like aglycone. This represents the first report of phytoanticipins occurring in M. acuminata.     

Aesculus pavia foliar saponins: defensive role against the leafminer Cameraria ohridella

BACKGROUND: Recently, the leafminer Cameraria ohridella Deschka & Dimic has caused heavy damage to the white‐flowering horse chestnut in Europe. Among the Aesculus genus, A. pavia L. HBT genotype, characterised by red flowers, showed an atypical resistance towards this pest. Its leaves, shaken in water, originated a dense foam, indicating the presence of saponins, unlike the common horse chestnut tree. The aim was to isolate and identify these leaf saponins and test their possible defensive role against C. ohridella. RESULTS: Spectroscopic analyses showed that A. pavia HBT genotype leaves contained a mixture of saponins, four of which were based on the same structure as commercial escin saponins, the typical saponin mixture produced by A. hippocastanum and accumulated only within bark and fruit tissues. The mixture showed a repellent effect on C. ohridella moth. The number of mines detected on the leaves of A. hippocastanum plants treated with A. pavia HBT saponins through watering and stem brushing was significantly lower than the control, and in many cases no mines were ever observed. CONCLUSION: The results showed that the exogenous saponins were translocated from roots/stem to the leaf tissues, and their accumulation seemed to ensure an appreciable degree of protection against the leafminer. Copyright © 2010 Society of Chemical Industry     

Increased activity and reduced sensitivity of glutamine synthetase in glufosinate‐resistant vetiver (Vetiveria zizanioides Nash) cells

Vetiver (Vetiveria zizanioides Nash) cells derived from an inflorescence were cultured in a modified N6 liquid medium supplemented with 10 µm 2,4‐D and 10 mm proline. Exponentially growing cell suspensions were subcultured with a selection medium containing glufosinate (ammonium dl ‐homoalanin‐4‐yl(methyl)phosphinate). The glufosinate‐resistant cells which can grow in a medium containing 5 × 10^?5 M glufosinate was selected by a stepwise selection, and its I₅₀ value was determined to be 4.2 × 10^?5 M. The growth of susceptible cells was inhibited by lower concentrations of glufosinate and its I₅₀ value was 2.5 × 10^?7 M. This indicated that the selected cells were 170‐fold resistant compared with the susceptible cells. Glutamine synthetase (GS) activity of the resistant cells was twice as high as that of the susceptible cells. The I₅₀ values of glufosinate were 3.2 × 10^?5 M and 9.0 × 10^?7 M for GS from the resistant and susceptible cells, respectively. The accumulation of ammonia caused by GS inhibition was higher in the susceptible cells. Absorption of [3,4–¹⁴C]glufosinate was not significantly different between the resistant and susceptible cells. Both cell types did not metabolize glufosinate. These results suggest that the resistance of the selected vetiver cell suspension to glufosinate is mainly due to increased GS activity and its decreased sensitivity to the herbicide.