Fluorescent molecular rotors as versatile in situ sensors for protein quantitation

Accurate protein quantitation is essential for many cellular mechanistic studies. Existing technology relies on extrinsic sample evaluation that requires significant volumes of sample as well as addition of assay-specific reagents and importantly, is a terminal analysis. This study exploits the unique chemical features of a fluorescent molecular rotor that fluctuates between twisted-to-untwisted states, with a subsequent intensity increase in fluorescence depending on environmental conditions (e.g., viscosity). Here we report the development of a rapid, sensitive in situ protein quantitation method using ARCAM-1, a representative fluorescent molecular rotor that can be employed in both non-terminal and terminal assays.

Potential insecticidal extracts from Artocarpus lacucha against Spodoptera litura (Lepidoptera: Noctuidae) larvae

Artocarpus lacucha, a plant in the Moraceae family, has traditionally been used in Southeast Asian medicine to treat various ailments. This study investigated the insecticidal potential against Spodoptera litura of several compounds extracted from A. lacucha using a topical application method. A sequential extraction method was employed with A. lacucha stems to identify the most toxic crude extract by using hexane, dichloromethane, ethyl acetate, and methanol solvents. Subsequently, the most toxic crude extract was analyzed for chemical composition by HPLC, followed by the isolation process. Among these crude extracts, the ethyl acetate crude extract was the most toxic to second-instar S. litura larvae (24-h LD50 value of ~9.07 µg/larva). Our results showed that the catechin isolated from the ethyl acetate crude extract exhibited the highest toxicity against this insect (24-h LD50 value of ~8.37 µg/larva). Additionally, catechin significantly decreased the activities of acetylcholinesterase, carboxylesterases, and glutathione S-transferase in the larvae. These findings suggest that catechin isolated from A. lacucha could be a potential insecticidal agent against S. litura. However, the toxicity and persistence of catechin under field conditions need to be further investigated to develop this novel insecticide.

Combination of 1H and 13C NMR for quantitative analysis of the orange pigments produced by Monascus kaoliang KB9

Two orange pigments, rubropunctatin (1) and monascorubrin (2), along with the yellow pigments, monascin (3) and ankaflavin (4), were isolated from M. kaoliang KB9-fermented rice, also known as red yeast rice. The orange pigments exhibit a broad spectrum of biological activities and appeared to be the major components of this fermented rice. In this work, quantitative ¹H NMR (qHNMR) and ¹³C NMR experiments were used to determine the amounts of the two orange pigments in a crude extract in which most of the ¹H NMR signals of the two compounds were indistinguishable. The quantitative values obtained by NMR techniques were found to be similar to those obtained by HPLC. Thus, the combined qHNMR with ¹³C experiment described in this work could be further developed to quantifying Monascus pigments or other invaluable natural products when qHNMR alone is insufficient for quantitative analysis.

Insecticidal activity of isolated gingerols and shogaols from Zingiber officinale Roscoe rhizomes against Spodoptera spp. (Lepidoptera: Noctuidae)

The discovery of eco-friendly plant-based insecticides is currently booming in research with an attempt to replace synthetic chemical insecticides causing tremendous adverse effects. The present work studied the insecticidal potential of ginger, an important medicinal plant. Four crude extracts from Zingiber officinale rhizomes were evaluated for their contact toxicity against second instars of Spodoptera litura, Spodoptera exigua and Spodoptera frugiperda using the topical application. The hexane extract exhibited the strongest toxicity to S. exigua with the LD50 of 9.92 and 8.40 µg/larva at 24 and 48 h posttreatment, respectively, followed by S. frugiperda. Comparative toxicity of the most abundant secondary metabolites from the hexane extract, gingerols and shogaols, against both insects concluded that 8-shogaol (5) was identified as the most active compound against S. frugiperda with the LD50 of 7.68 and 3.96 µg/larva at 24 and 48 h posttreatment, respectively.

Yellow Twig (Nauclea orientalis) from Thailand: Strictosamide as the Key Alkaloid of This Plant Species

Comprehensive phytochemical examination from different perspectives using preparative and analytical chromatographic techniques combined with spectroscopic/spectrometric methods of the so-called “yellow twig” Nauclea orientalis (L.) L. (Rubiaceae) led to the identification of 13 tryptamine-derived (=monoterpene-indole) alkaloids. The identified alkaloids comprise strictosamide and four of its glucosidic derivatives, three oxindole derivatives, and five yellow-colored angustine-type aglycones. Qualitative and quantitative HPLC analyses showed the enrichment of strictosamide in all studied organs. Based on these results, we performed metabolomic analyses of monoterpene-indole alkaloids and made a 1H NMR in vitro monitoring of enzymatic deglucosylation of strictosamide. A comparison of the stability of strictosamide and its enantiomer vincoside lactam by theoretical calculations was also performed revealing a slightly higher stability of vincoside lactam. Additionally, we conducted two different anti-feedant assays of strictosamide using larvae of the polyphageous moth Spodoptera littoralis Boisduval. The obtained results indicate that generally two different biosynthetic pathways are most likely responsible for the overall alkaloid composition in this plant. Strictosamide is the key compound in the broader pathway and most likely the source of the identified angustine-type aglycones, which may contribute significantly to the yellow color of the wood. Its cross-organ accumulation makes it likely that strictosamide is not only important as a reservoir for the further biosynthesis, but also acts in the plants’ defense strategy.

Insecticidal and growth inhibitory effects of some thymol derivatives on the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae) and their impact on detoxification enzymes

BACKGROUND

Thymol is a known natural product with insecticidal activity against several insect species. A recent study on structural modifications of thymol to thymyl esters and their efficacy against Spodoptera litura suggested that such an approach could develop generalized novel insecticides/insect growth inhibitors and requires further studies to establish the efficacy against lepidopterans.

RESULTS

Thymol and structurally modified eight esters were evaluated against beet armyworm, Spodoptera exigua using the topical application. Thymyl butanoate was the most toxic compound with a median lethal dose (LD₅₀ ) of 2.33 and 1.62 μg/larva after 24 and 48 h posttreatment, respectively. All thymyl esters were potentially better than the parent compound thymol, except thymyl dibromoacetate, in their efficacy against Spodoptera exigua. Essentially, there were three levels of activity vis-à-vis the compounds used, that is, with the LD₅₀ range of 1.5 to 5.0, 7.0 to 15.0, and > 20 μg/larva, respectively. Ovicidal activity and reduction in larval growth were also determined by treating third instars at sub-lethal doses, that is, LD₅₀ doses of second instars. Thymyl butanoate treated larvae inhibited glutathione S-transferase, carboxylesterase, and acetylcholinesterase activities, whereas the other thymyl esters induced these enzymes.

CONCLUSION

Thymyl butanoate exhibited higher toxicity against Spodoptera exigua and is the first to report about > 15.5× more toxicity than thymol and > 6.5× than thymyl cinnamate, which suggests that the efficacy was species-specific versus the chemical structural variation of the esters. © 2021 Society of Chemical Industry.

Highly Aromatic Flavan-3-ol Derivatives from Palaeotropical Artocarpus lacucha Buch.-Ham Possess Radical Scavenging and Antiproliferative Properties

Phytochemical investigation of leaves and stembark of Artocarpus lacucha collected in Thailand resulted in three yet undescribed isomeric flavan-3-ol derivatives (1–3), the four known compounds gambircatechol (4), (+)-catechin (5), (+)-afzelechin (6) and the stilbene oxyresveratrol (7). Compounds 1 to 3 feature 6/6/5/6/5/6 core structures. All structures were deduced by NMR and MS, while density functional theory (DFT) calculations on B3LYP theory level were performed of compounds 1 to 3 to support the stereochemistry in positions 2 and 3 in the C-ring. Possible biosynthetic pathways leading to 4 are discussed. The DPPH assay revealed high radical scavenging activities for 1 (EC₅₀ = 9.4 ± 1.0 µmol mL⁻¹), 2 (12.2 ± 1.1), 3 (10.0 ± 1.5) and 4 (19.0 ± 2.6), remarkably lower than ascorbic acid (EC₅₀ = 34.9) and α-tocopherol (EC₅₀ = 48.6). A cytotoxicity assay revealed moderate but consistent antiproliferative properties of 1 in CH1/PA-1 (ovarian teratocarcinoma) and SW480 (colon carcinoma) cells, with IC₅₀ values of 25 ± 6 and 34 ± 4 µM, respectively, whereas effects in A549 (non-small cell lung cancer) cells were rather negligible. The performed DCFH-DA assay of 1 in the former cell lines confirmed potent antioxidative effects even in the cellular environment.

Insecticidal activity of isolated phenylpropanoids from Alpinia galanga rhizomes against Spodoptera litura

Botanical insecticides as a means of controlling insects present an alternative approach that is safer than the use of synthetic insecticides. The present study identified the insecticidal activity of extracts of the rhizomes of Alpinia galanga (L.) Willd. and seven isolated phenylpropanoids against the second instar of Spodoptera litura Fab. by topical application. The ethyl acetate extract had the highest toxicity on this insect with LD₅₀ values of 1.68 and 1.25 μg/larva after 24 and 48 h posttreatment, respectively. Among the seven phenylpropanoids separated from the ethyl acetate extract, 1'S-1'-acetoxychavicol acetate was identified as the most active compound with LD₅₀ values of 1.63 and 1.40 μg/larva after 24 and 48 h posttreatment, respectively, followed by p-coumaryl diacetate. In addition, the two active compounds decreased glutathione S-transferase activity and increased acetylcholinesterase activity. p-Coumaryl diacetate also decreased carboxylesterase activity.

Synthesis of thymyl esters and their insecticidal activity against Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND

Thymol, a natural phenolic monoterpene originating from Thymus vulgaris, is recognized as a safe and potent botanical insecticide to many insects. The structural modification of thymol into thymyl esters is a potential approach for the development of novel insecticides, which showed more toxicity than thymol. However, there are no reports on the insecticidal activity of thymyl esters to control Spodoptera litura.

RESULTS

Thymol was structurally modified into ten thymyl esters by esterification using a new reagent, PPh₃ /Br₃ CSO₂ Ph. The insecticidal activity of these compounds was examined against the second instars of Spodoptera litura using a topical application. Among the ten thymyl esters evaluated, thymyl cinnamate was the most toxic with LD₅₀  = 0.41 and 0.34 μg/larva after 24 and 48 h posttreatment, respectively. In addition, thymyl cinnamate-treated larvae showed increasing carboxylesterase and acetylcholinesterase activities in vivo experiment, whereas glutathione S-transferase activity showed no significant difference.

CONCLUSION

Thymyl cinnamate were first reported to exhibit toxicity against S. litura 2.41-2.46 fold more efficient than thymol. However, the detailed biochemical interactions are necessary for further development of novel insecticides. © 2019 Society of Chemical Industry.

Effect of Plant Essential Oils and Their Major Constituents on Cypermethrin Tolerance Associated Detoxification Enzyme Activities in Spodoptera litura (Lepidoptera: Noctuidae)

Essential oils are well known to act as biopesticides. This research evaluated the acute toxicity and synergistic effect of essential oil compounds in combination with cypermethrin against Spodoptera litura Fabricius (Lepidoptera: Noctuidae). The effects of distillation extracts of essential oils from Alpinia galanga Zingiberaceae (Zingiberales) rhizomes and Ocimum basilicum Lamiaceae (Lamiales) leaves; one of their primary essential oil compounds 1,8-cineole; and linalool were studied on second-instar S. litura by topical application under laboratory conditions. The results showed that A. galanga had the highest control efficiency, whereas1,8-cineole provided a moderate efficacy. The mixtures of linalool, 1,8-cineole, O. basilicum, or A. galanga with cypermethrin were synergistic on mortality. Activity measurements of the main detoxification enzymes show that linalool and 1,8-cineole inhibit the activity of cytochromes P450 and carboxylesterases, which could explain their synergistic effect. Based on our results, the use of these mixtures represents an ideal eco-friendly approach, helping to manage cypermethrin resistance of S. litura.

The Study of Isolated Alkane Compounds and Crude Extracts From Sphagneticola trilobata (Asterales: Asteraceae) as a Candidate Botanical Insecticide for Lepidopteran Larvae

The antifeedant and contact toxicity of Sphagneticola trilobata L. (Asterales: Asteraceae) extracts and isolated alkane compounds were investigated. Leaves of S. trilobata were sequentially extracted with hexane, dichloromethane, ethyl acetate, and methanol. Each extract and the compounds isolated were evaluated against the third instars of Spodoptera litura (F.) (Lepidoptera: Noctuidae), Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), and Plutella xylostella L. (Lepidoptera: Yponomeutidae). Ethyl acetate extract and isolated alkanes were feeding deterrents as well as contact toxins against all the three species evaluated (FI50 ~ 0.27-2.34 mg/ml; LD50 ~ 0.88-4.2 µg/larvae for ethyl acetate extract, and FI50 ~ 0.06-4.35 mg/ml; LD50 ~ 0.72-3.54 Ethyl acetate extract for isolated alkane). Impact on detoxifying enzymes was variable. The ethyl acetate crude extract reduced carboxylesterase activity in S. litura and P. xylostella while in S. exigua the enzyme was induced. In contrast, glutathione-S-transferase activity was induced in S. exigua but no significant difference in P. xylostella and S.litura was observed. Our results suggest that the S. trilobata extracts have multiple biological activities that contribute to the toxicity in lepidopterans. Variable enzyme responses to the products evaluated in different lepidopteran species also confirm that some species-specific inductions do occur, suggesting the possibility of resistance development in the future, which cannot be summarily ignored. However, for this detailed biochemical studies are required. Multiple bioefficacies of S. trilobata makes it a potential botanical for further exploitation on larger scale so that field potential can be established in any integrated pest management (IPM) system.

The Possibility of Using Isolated Alkaloid Compounds and Crude Extracts of Piper retrofractum (Piperaceae) as Larvicidal Control Agents for Culex quinquefasciatus (Diptera: Culicidae) Larvae

Culex quinquefasciatus is a common domestic mosquito that is widespread in many areas of Thailand and serves as a southeastern vector of Japanese encephalitis. The present study investigated the acute toxicity of crude extracts and alkaloid compounds of Piper retrofractum (Piperales: Piperaceae) in Cx. quinquefasciatus third instar larvae. P. retrofractum was sequentially extracted using hexane, dichloromethane, ethyl acetate, and methanol, and the crude extracts were tested on mosquito larvae. Detoxification and neuroenzymes were analyzed to establish the mode of action. Acute toxicity was assessed on Poecilia reticulata (Cyprinodontiformes: Poeciliidae) to determine the possibility of toxicity in a nontarget species. Our results showed crude hexane extract had the highest toxicity in Cx. quinquefasciatus (0.9 ppm). Piperine and piperanine, which are alkaloid compounds from the crude hexane extract, showed LC50 values of 0.27 and 2.97 ppm, respectively, after 24 h of exposure. All the crude extracts showed low toxicity in P. reticulata compared with that in the mosquito larvae. The carboxylesterase, glutathione-S-transferase, and acetylcholinesterase activities in Cx. quinquefasciatus were reduced after treatment with all the extracts and the two alkaloid compounds. Thus, P. retrofractum shows larvicidal effects against Cx. quinquefasciatus and low toxicity for nontarget species. Thus, P. retrofractum could be a choice for controlling Cx. quinquefasciatus.

Four-component synthesis of polyhydroquinolines under catalyst- and solvent-free conventional heating conditions: mechanistic studies

A convenient and environmentally friendly procedure for the synthesis of polyhydroquinolines via a one-pot four-component reaction has been developed. A detailed mechanistic study of the reaction is presented.

INSECTICIDAL ACTIVITIES OF THYMOL ON EGG PRODUCTION AND DEVELOPMENT IN THE DIAMONDBACK MOTH, PLUTELLA XYLOSTELLA (LEPIDOPTERA)

The insecticidal activity of thymol was evaluated in the laboratory against third instar Plutella xylostella by topical application. Our previous results described mortality in P. xylostella by thymol and the present study continues investigation for its possible efficacy on egg production and development in surviving treated P. xylostella. Our results showed that thymol at a sublethal dose (0.43 µg/larvae, LD₃₀) caused pupation inhibition, adult-emergence inhibition and abnormal adults at rates of 30, 33.33 and 23.33%, respectively. Moreover, the number of eggs was also reduced by 54.33%. These results showed that thymol was active against P. xylostella larvae and can effectively control this pest.

EFFECTS OF AZADIRACHTIN ON CUTICULAR PROTEINS OF SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE) VIS-A-VIS THE MODES OF APPLICATION

Azadirachtin is a known botanical insecticide with multiple modes of action. Whether these effects have any relation with the modes of application, specifically during ecdysis process, has been the objective of the present study and accordingly the impairment, if any, among cuticular proteins of Spodoptera litura (Fab.) was determined. Azadirachtin was applied topically, via injection or oral administration. Azadirachtin administered via injection and topical applications severely impaired the ecdysis by 86.67 and 80.0%, respectively. However, this impairment via oral administration was significantly lower (73.33%). Using SDS-PAGE, the cuticular proteins were determined for treated insects under all the three modes of application. In all cases 6 protein bands (MW 9-34 kDa) were identified using markers as standard. In all treatments 3 induced proteins (MW. ~16, 20 and 23 kDa) and 1 reduced protein (~19 kDa) were observed. In case of the topical treatment a different induced protein of ~18 kDa was identified. The change in cuticular proteins, their possible role in ecdysis impairment vis-a-vis the mode of application of azadirachtin is being correlated. This will help in understanding the mode-of-action at cuticular level and also will allow developing a suitable application strategy under field conditions in insect pest management.

TOXICITY OF THE SEEDS OF PHASEOLUS LATHYROIDES (LEGUMINOSAE) AGAINST SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE)

The seeds of Phaseolus lathyroides were extracted with hexane, dichloromethane, ethyl acetate and methanol, respectively by Soxhlet apparatus. Each crude extract was examined for toxicity against the second instars of Spodoptera litura using a topical application method under laboratory conditions. The ethyl acetate extract showed the most effective mortality (LD₅₀ = 11,964 and 9,169 ppm after treated at 24 and 48 hours, respectively). Furthermore, in vivo enzyme based experiments revealed that acetylcholinesterase activity of survived S. litura (24 hours post-treatment) was increased by 12% compared to control experiments. Our result showed the possibility to develop alternative strategies by using extract from the seeds of Phaseolus lathyroides for the control of S. litura.

[BIO-INSECTICIDAL ACTIVITY OF ALPINIA GALANGA (L.) ON LARVAL DEVELOPMENT OF SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE)

The aim of the study was to assess the bio-efficacy of four Alpinia galanga rhizome crude extracts against the second and third instars of Spodoptera litura, an important field pest. The growth of younger larvae was significantly affected while that of the older larval stage was less influenced. In both stages, the methanol crude extract showed the greatest efficiency which caused the highest number of abnormal adults to occur and produced a large LD₅₀ value (12.816 µg/ larvae) pupicidal percentage after treatment, whereas, hexane extract caused the highest mortality during the larval-pupal stage after treatment with an LD₅₀ value of 6.354 µg/ larvae. However, the larval development was not significantly different among all treated larvae compared to the control. This study suggests that secondary larval instars of S. litura are more susceptible to the larval growth inhibitory action of Alpinia galanga extracts and these extracts could also be applied for use in the management of pests.

ANTIFEEDANT ACTIVITY OF CRUDE EXTRACTS FROM STEMS AND LEAVES OF TADEHAGI TRIQUETRUM (L.) OHASHI AND SEEDS OF PHASEOLUS LATHYROIDES AGAINST HELICOVERPA ARMIGERA HÜBNER (LEPIDOPTERA: NOCTUIDAE)

Efficacy of hexane, dichloromethane, ethyl acetate, and methanol crude extracts of stems and leaves of Tudehagi triquetrum (Legumin: Papilionaceae) and seeds of Phaseolus lathyroides (Leguminiale: Papilionaceae) was examined for the antifeedant activity against third instars larvae of Helicoverpa armigera using leaf disc no-choice method in the range of 0 to 2% concentrations for 6 and 12 hours. The ethyl acetate extract from T. triquetrum was the most effective at 6 hours with FI50 of 0.5346%, while the hexane extract from P. lathyroides only exhibited 0.7228% FI50 value at 6 hours. The antifeedant effect appeared to be time and concentration dependent, i.e. feeding deterrence depleted with increased exposure. Moreover, it is obvious from our study that both extracts could be used under short-term applications in an integrated pest management strategy of pest control.

TOXICITY OF ALPINIA GALANGA (ZINGIBERACEAE) RHIZOME EXTRACTS AGAINST SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE)

The objective of this study was to develop an alternative strategy for the control of Spodoptera litura larvae by using botanical insecticides. Rhizomes of Alpinia galanga were extracted with hexane, dichloromethane, ethyl acetate and methanol, respectively. Each crude extract was examined for toxicity against the second instars of S. litura according to a topical application method. The dichloromethane extract was found to show the highest toxicity of all the extracts, with LD50 = 3177 and 2099 ppm at 24 and 48 h post-treatment, respectively.

BIOEFFICACY OF PIPER RIBESIOIDES (PIPERACEAE) EXTRACTS AGAINST NILAPARVATA LUGENS STAL. (HOMOPTERA: DELPHACIDAE)

The extracts of stem and seeds of Piper ribesioides (Piperaceae) were prepared in hexane, dichloromethane, ethyl acetate and ethanol and evaluated for their efficacy against 3-day-old adult brown plant hoppers, Nilaparvata lugens Stal under laboratory conditions. The treatment was given topically and results suggest the dose dependent response related to exposure time. The ethyl acetate extract was the best with an LC50 = 738 ppm-, 24 h post-treatment. There was substantial increase in activity (LC50 = 27.298 ppm) with the increase in duration of exposure. This trend was observed in all treatments that suggests the potential of Piper ribesioides as an insecticide for N. lugens as an alternative control.

Bio efficacy of some piperaceae plant extracts against Plutella xylostella L. (Lepidoptera: Plutellidae)

The extracts of Piper sarmentosum Roxb., Piper retrofractum Vahl, Piper interruptum Opiz and Piper nigrum plants belonging to the family Piperaceae were evaluated for their efficacy against diamondback moth, Plutello xylostella L. third instars under laboratory conditions. Comparative toxicity of various extracts prepared in hexane, dichloromethane, ethyl acetate and ethanol following sequential extraction procedure were applied topically to the larvae. The hexane extract of Piper retrofractum was most active (LD = 237 ppm). The toxicity was dose dependant and correlated to duration of exposure. The hexane extract of P. nigrum was least active with an LD50 of 18,435 ppm. The mode of action of these extracts and effect on other developmental parameters is in progress.

Toxicological study of Wedelia trilobata (Asteraceae) extracts as alternative control strategies for Plutella xylostella (Lepidoptera: Plutellidae)

The Diamondback moth (Plutella xylostella (L)) is an economically important pest in Thailand and the indiscriminant use of chemical pesticides against this pest has been responsible for environmental hazards. Present research, therefore, is trying to develop alternative strategies by using plant based-products for the control of this pest. Wedelia trilobata (L) Hitchc extracts prepared in hexane, dichloroethane, ethyl acetate and ethanol were used initially against the second instars of P. xylostella by topical application to determine the dose dependent toxicity. The highest yield of the extracts was obtained with EtOH extract followed by hexane, EtOAc and dichloroethane. However, the EtOAc extract exhibited the highest toxicity (24h-LC50 = 442.8 ppm) that became more prominent after 48 h (LC50 = 376.71 ppm). This suggests there was an increase in toxicity with the duration of exposure to the treatment. With the exception of the hexane extract, all other treatments were significantly correlated, which suggests that W. trolobata contains a varied profile of anti-insect allelochemicals that can be exploited in any integrated pest management strategy. The identification of the active ingredients is in progress.

Bioefficacy of Alpinia galanga (Zingiberaceae) rhizome extracts, (E)-p-acetoxycinnamyl alcohol, and (E)-p-coumaryl alcohol ethyl ether against Bactrocera dorsalis (Diptera: Tephritidae) and the impact on detoxification enzyme activities

The application of insecticides to control oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae), is a principal component of the current management of these fruit flies. However, we evaluated four extracts of Alpinia galanga Wild Linn (Zingiberaceae) rhizomes against adult flies and found hexane and ethanol extracts to be most effective (LC50 = 4,866 and 6,337 ppm, respectively, after 24 h). This suggested that both nonpolar and polar compounds could be active in the candidate plant. Accordingly, the hexane extract was further processed to isolate nonpolar active compounds from this plant source. Two compounds, (E)-p-acetoxycinnamyl alcohol and (E)-p-coumaryl alcohol ethyl ether, were identified as active ingredients and found to be more active than total hexane extract (LC50 = 3,654 and 4,044 ppm, respectively, after 24 h). The data suggested that the compounds were not synergistic but may have some additive effect in a mixture. The activity of the hexane extract against detoxification enzymes, carboxylesterase (CE) and glutathione transferase (GST) also was determined in vitro. CE was inhibited by 70%, whereas GST was not significantly inhibited. Insect CEs mediate insecticide resistance via their induction; therefore, inhibition of these enzymes by plant allelochemicals could be a useful alternative approach for the management of the pest in the field.

Toxicity of ethyl acetate extract from Jatropha gossypifolia senescent leaves against Spodoptera exigua Hübner (Lepidoptera: Noctuidae) and Meteorus pulchricornis (Hymenoptera: Braconidae)

This study explored the insecticidal effects of Thai botanical, senescent leaf Jatropha gossypifolia extracts on second instar Spodoptera exigua larvae by the dipping method and topical sprayer method. The leaf crude extract was extracted using Soxhlet apparatus with ethyl acetate as solvent. The leaf crude extracts showed insecticidal activity with a LC50 of 6182 ppm at 24 hours after treatment. In addition, this research was observed its toxicity to worm parasitoid, Meteorus pulchricornis by contact method. The result shows 60 percent mortality of this parasitoid species at dose up to 40,000 ppm. Thus, Jatropha gossypifolia leaf crude extracts can be as alternative IPM control tool for Spodoptera exigua which friendly to benefit insect such as Meteorus pulchricornis.

Impact of Alpinia galanga rhizome extract on Bactrocera dorsalis population

The Bactrocera dorsalis (Hendel) is one of the most economically damaging pests and generally is controlled by insecticides. This research was done by evaluate the impact of rhizomes of Alpinia galanga extract on population of B. dorsalis. The rhizome of A. galanga was extracted by Soxhlet's apparatus using hexane, dichloromethane, ethyl acetate and 95% ethanol as separated solvent system. Various concentrations of all crude extracts were trailed by Topical spray application with adult B. dorsalis, completely randomized designs, 5 replicates. The results showed hexane crude extract gave the highest control efficiency to adult B. dorsalis which the 24 hours-LC50 values was 4,866.06 +/- 184.52 ppm (hexane), 24,156.66 +/- 880.33 ppm (dichloromethane), 16,744.73 +/- 641.27 ppm (ethyl acetate) and 6,337.54 +/- 145.42 ppm (95% ethanol). Thus, this extract may an alternative way for control this insect pest in the future.

Synthesis of N-phenylphthalimide derivatives as alpha-glucosidase inhibitors

Sixteen N-phenylphthalimide derivatives were synthesized and their ability to inhibit alpha-glucosidase was investigated. N-(2,4-dinitrophenyl)phthalimide was a potent inhibitor of yeast alpha-glucosidase (IC50; 0.158 +/- 0.005 mM) and maltase (IC50; 0.051 +/- 0.008 mM), whereas it did not inhibit sucrase. From a Lineweaver-Burk plot of alpha-glucosidase kinetics, N-(2,4-dichlorophenyl)phthalimide was found to be a competitive inhibitor of yeast alpha-glucosidase. These results indicate that N-(2,4-dinitrophenyl)phthalimide could be a representative of a new group of alpha-glucosidase inhibitors.