Biological activity of natural phytoecdysteroids from Ajuga iva against the sweetpotato whitefly Bemisia tabaci and the persea mite Oligonychus perseae

Chemical Composition, Antioxidant, and Antimicrobial Activities of Leaves of Ajuga Iva

The main objective of this research was to study the biological characteristics in terms of antioxidant and antimicrobial activities of Ajuga iva and determine the best analytical and extraction methods applicable to this specie and studied compounds. A short screening of its nutritional value in terms of chemical composition is also included. A. iva leaves were analyzed for crude protein (CP), cell wall [neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL)], minerals, fatty acids, essential oils, and phenolic compounds. Mature aerial parts of A. iva were randomly collected during the Spring season from Mograne-Zaghouan, Tunisia. Leaves of A. iva contained 13.4 ± 0.4% CP, 26.3 ± 0.35% NDF, 20.2 ± 0.42% ADF, and 5.13 ± 0.21% ADL. Mineral content (13.0 ± 0.45%) was mainly composed of potassium (4.5% g DM) and magnesium (4.25% DM). Leaves of A. iva had linolenic (26.29 ± 0.760%) and linoleic (37.66 ± 2.35%) acids as the main components of the acid profile. Thymol was found to be the most dominant (23.43%) essential oil, followed by 4-vinylguaiacol (14.27%) and linalool (13.66%). HPLC-PDA-ESI-MS/MS analysis pointed out the presence of phytoecdysteroids. Phenolic acids and flavonoids, such as glycosylated derivatives of naringenin, eriodyctiol, and apigenin, were detected in the methanol extract of A. iva leaves. Our results underline the importance of choosing proper extraction methods and solvents to extract and characterize the described compounds profile of A. iva leaves. Results also show A. iva leaves as a potential source of functional ingredients with beneficial health-promoting properties. Overall, leaves of A. iva have low biological activities (antioxidant and antimicrobial activities) with a chemical composition suitable as a feed for ruminants in rangeland pasture. It also has low-grade antibacterial or medicinal characteristics when fed to ruminants.

Identification of Genes Involved in Resistance to High Exogenous 20-Hydroxyecdysone in Spodoptera litura

Simple Summary

20-hydroxyecdysone (20E), the most active insect ecdysteroids, is also a major form of phytoecdysteroids in some plants. The phytoecdysteroid from plant is generally considered as defensive weapon to prevent ingestion by phytophagous insects. Conversely, insects also evolved resistance mechanisms to combat the plant defensive system. In this study, we dissected the molecular mechanism to explain how noctuid pest (Spodoptera litura) resist high dosage of 20E. Besides, comparative transcriptomic analysis using two noctuid insects (S. litura and Helicoverpa armigera) also revealed that different species always ultilized various starategies to tolerate ingested hormone.

Abstract

To prevent their ingestion by phytophagous insects, plants produce secondary metabolites as defensive weapons. Conversely, insects need to counter these metabolites to survive. Different species, though they are closely related, can evolve distinct strategies to resist plant-derived factors. However, the mechanism under this high divergence resistance is still unclear at a molecular level. In this study, we focus on how Spodoptera litura (Lepidoptera; Noctuidae) detoxifies phytoecdysteroids, a class of metabolites capable of disrupting the normal development of insects. Firstly, we find that the S. litura show resistance to artificial foods containing a high level of 20-hydroxyecdysone (20E), the major form of phytoecdysteroids, without any adverse effects on growth and development. Furthermore, a comparative transcriptomic analysis between S. litura and another noctuid insect (Helicoverpa armigera) was performed. Almost all known ecdysteroid degradation pathways including 3-epimerization, 22-phosphorylation, 22-esterification, and 26-hydroxylation were upregulated in the midgut of 20E treated S. litura larvae, whereas only 22-esterification and 26-hydroxylation were enhanced in H. armigera larvae. In summary, though both species belong to the Noctuidae family, they evolved two different strategies to tolerate a high dosage of ingested 20E.

Activity of Ajuga iva Extracts Against the African Cotton Leafworm Spodoptera littoralis

Control of the crop pest African cotton leafworm, Spodoptera littoralis (Boisduval), by chemical insecticides has led to serious resistance problems. Ajuga plants contain phytoecdysteroids (arthropod steroid hormone analogs regulating metamorphosis) and clerodanes (diterpenoids exhibiting antifeedant activity). We analyzed these compounds in leaf extracts of the Israeli Ajuga iva L. by liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) and thin-layer chromatography (TLC), and their efficiency at reducing S.littoralis fitness. First and third instars of S. littoralis were fed castor bean leaves (Ricinus communis) smeared with an aqueous suspension of dried methanolic crude extract of A. iva phytoecdysteroids and clerodanes. Mortality, larval weight gain, relative growth rate and survival were compared to feeding on control leaves. We used '4',6-diamidino-2-phenylindole (DAPI, a fluorescent stain) and phalloidin staining to localize A. iva crude leaf extract activity in the insect gut. Ajuga iva crude leaf extract (50, 100 and 250 µg/µL) significantly increased mortality of first-instar S. littoralis (36%, 70%, and 87%, respectively) compared to controls (6%). Third-instar larval weight gain decreased significantly (by 52%, 44% and 30%, respectively), as did relative growth rate (-0.05 g/g per day compared to the relevant controls), ultimately resulting in few survivors. Crude leaf extract (250 µg/µL) reduced gut size, with relocation of nuclei and abnormal actin-filament organization. Ajug iva extract has potential for alternative, environmentally safe insect-pest control.

Optimization of Insecticidal Triterpene Derivatives by Biomimetic Oxidations with Hydrogen Peroxide and Iodosobenzene Catalyzed by MnIII and FeIII Porphyrin Complexes

Semisynthetic functionalized triterpenes (4α,14-dimethyl-5α,8α-8,9-epoxycholestan-3β-yl acetate; 4α,14-dimethyl-5α-cholest-8-ene-3,7,11-trione; 4α,14-dimethyl-5α-cholesta-7,9(11)-dien-3-one and 4α,14-dimethyl-5α-cholest-8-en-3β-yl acetate), previously prepared from 31-norlanostenol, a natural insecticide isolated from the latex of Euphorbia officinarum, have been subjected to oxidation with hydrogen peroxide (H₂ O₂ ) and iodosobenzene (PhIO) catalyzed by porphyrin complexes (cytochrome P-450 models) in order to obtain optimized derivatives with high regioselectivity. The main transformations were epoxidation of the double bonds and hydroxylations of non-activated C-H groups and the reaction products were 25-hydroxy-4α,14-dimethyl-5α-cholesta-7,9(11)-dien-3β-yl acetate (59 %), 25-hydroxy-4α,14-dimethyl-5α-cholest-8-ene-3,7,11-trione (60 %), 4α,14-dimethyl-5α,7β-7,8-epoxycholest-9(11)-en-3-one (22 %), 8-hydroxy-4α,14-dimethyl-5α-cholest-9(11)-ene-3,7-dione (16 %), 12α-hydroxy-4α,14-dimethyl-5α,7β-7,8-epoxycholest-9(11)-en-3-one (16 %), and 4α,14-dimethyl-5α,8α-8,9-epoxycholestan-3β-yl acetate (26 %), respectively. We also investigated the insect (Myzus persicae, Rhopalosiphum padi and Spodoptera littoralis) antifeedant and postingestive effects of these terpenoid derivatives. None of the compounds tested had significant antifeedant effects, however, all were more effective postingestive toxicants on S. littoralis larvae than the natural compound 31-norlanostenol, with 4α,14-dimethyl-5α,8α-8,9-epoxycholestan-3β-yl acetate being the most active. The study of their structure-activity relationships points out at the importance of C3 and C7 substituents.

Ethnomedicinal use, phytochemistry, pharmacology, and toxicology of Ajuga iva (L.,) schreb

ETHNOPHARMACOLOGICAL RELEVANCE

Ajuga iva (L.,) Schreb (A. iva). is a medicinal plant commonly used in Africa to treat several diseases such as diabetes, rheumatism, allergy, cancer, renal, metabolic disorders, cardiovascular disorders, digestive, and respiratory disorders.

AIM OF THE REVIEW

We highlighted previous reports on A. iva including its ethnopharmacological uses, the chemistry of its secondary metabolites, in vitro and in vivo pharmacological properties, and toxicological evidence.

MATERIALS AND METHODS

The data on A. iva were gathered using scientific research databases such as ScienceDirect, PubMed, SpringerLink, Web of Science, Scopus Wiley Online, and Google Scholar. In this review, studies focused on A. iva and its phytopharmacological activities were explored.

RESULTS

A. iva is used by many North African folk medicine practitioners especially against diabetes and immunological diseases. Our analysis of the previous reports confirmed the scientific evidence of A. iva ethnomedicinal uses, especially the antidiabetic and anti-hypercholesterolemia activity. However, there was no clear correlation between previous pharmacological reports on A. iva and its other ethnomedicinal uses in the treatment of rheumatism, allergy, metabolic, digestive, and respiratory disorders. The extracts and isolated compounds from A. iva exhibited numerous in vitro and in vivo pharmacological activities such as antidiabetic, antioxidant, antimicrobial, anti-hypercholesterolemia, insecticide, and litholitic effects. Chemical characterization using GC-MS, HPLC, and NMR revealed the presence of many chemical compounds such as 20-hydroxyecdysone, cyasterone, ajugasterone, apigenin dihexoside, apigenin, carvacrol, ecdysterone, palmitic acid in different parts of A. iva. These compounds belong to different classes of chemical compounds such as steroids, flavonoids, fatty acids, and terpenoids.

CONCLUSIONS

A. iva extracts especially from the leaves showed significant antidiabetic, antioxidant, anti-hypercholesterolemia, and analgesic effects. Future studies are required to validate the results of clinical trials on A. iva antidiabetic, anti-hypercholesterolemia, antioxidant/anti-inflammatory, antimicrobial, and analgesic properties. Toxicological validation and pharmacokinetics investigation are necessary to validate the efficacy and safety A. iva extracts and its secondary metabolites. An in-depth investigation is needed to reveal the biological activity of A. iva active compounds in preventing the development of cancer and neurodegenerative disorders such as Alzheimer's and Parkinson's diseases.

Identification and Characterization of Genes Involved in Ecdysteroid Esterification Pathway Contributing to the High 20-Hydroxyecdysone Resistance of Helicoverpa armigera

20-Hydroxyecdysone (20E), the most important regulator for insect development, is also a major component in phytoecdysteroids in plants. Therefore, this plant-derived hormone is considered as a potential natural product for use in pest management. However, some insects show high resistance to it, and the molecular mechanism of their resistance is still unclear. In this study, we find that the cotton bollworm Helicoverpa armigera larvae show high tolerance to artificial foods containing up to 50 μg 20E without any detrimental effects on growth and development. High performance liquid chromatography analysis indicates that high efficiency to transform the ingested 20E through an ecdysteroid esterification pathway may contribute to the resistance. Furthermore, comparative transcriptome analysis of the larvae's midgut after 20E treatment identifies two genes (long-chain-fatty-acid-CoA ligase, Long-FACL; sterol O-acyltransferase, SATF) involved in the pathway. Transcriptome and real-time PCR show the Long-FACL gene can be significantly induced by 20E, and this induction is only detected in the midgut. However, 20E has no effect on the transcript of the SATF gene. Moreover, the heterologously expressed protein of the SATF gene shows the ecdysteroid-22-O-acyltransferase activity that requires fatty acyl-CoA, which is produced by Long-FACL. Taken together, our results identify and demonstrate the genes involved in the ecdysteroid esterification pathway conferring high resistance to 20E in the cotton bollworm, H. armigera.

Phytoecdysteroids as antifeedants towards several beetles that include polyphagous and monophagous feeding guilds

BACKGROUND

Plants are thought to produce ecdysteroids as a means of protection from insect herbivores. Some insects will not feed on plants containing high amounts of phytoecdysteroids, and this response could be limited to monophagous and oligophagous insects. The aim of this study was to determine whether phytoecdysteroids could inhibit feeding in several species of beetles that range from monophagous to polyphagous.

RESULTS

Here we demonstrate that phytoecdysteroids, including 20-hydroxyecdysone, prevent several beetle species from feeding on preferred host plants, including the polyphagous Japanese beetle Popillia japonica (Scarabaeidae). Phytoecdysteroids prevented feeding damage when sprayed onto soybean plants in no-choice and choice assays in a dose-dependent manner. Laboratory assays indicate that other plants could be protected from Japanese beetle herbivory, including linden, wild grape, elm, Virginia creeper and rose leaves. Additional beetle species tested in the family Chrysomelidae included the oligophagous Cerotoma trifurcata and Diabrotica virgifera virgifera and the monophagous Trirhabda canadensis. All species were prevented from feeding when their preferred host plants were treated with phytoecdysteroids.

CONCLUSION

This study demonstrates that beetles, representing polyphagous and monophagous feeding guilds, can be prevented from feeding when phytoecdysteroids are applied to the leaf surface. The phytoecdysteroids could be utilized in pest management towards a variety of beetles, including the more pestiferous polyphagous species, if the compounds are placed on the leaf surface. © 2016 Society of Chemical Industry.

New Bioactive Semisynthetic Derivatives of 31-Norlanostenol and Obtusifoliol from Euphorbia Officinarum

Fifteen semisynthetic terpenoid derivatives from the major latex components of Euphorbia officinarum have been evaluated against the insect pest Spodoptera littoralis, two species of protozoan parasites, Trypanosoma cruzi and Leishmania infantum, and also against insect Sf9 and mammalian CHO cells to test their selective cytotoxicity. Our results showed that 40% of the test substances were postingestive toxicants to S. littoralis. All the tested derivatives had cytotoxic effects on insect-derived Sf9 cells, whereas mammalian CHO cells were affected by a lower number of compounds (47%). Furthermore, 87% of the test compounds had antiparasitic effects on bothi. infantum and T. cruzi, with some of them being selective parasite toxicants.

The effect of rol genes on phytoecdysteroid biosynthesis in Ajuga bracteosa differs between transgenic plants and hairy roots

A. bracteosaplants transformed withrolgenes biosynthesize higher phytoecdysteroid contents (up to 14.5 fold) as compared to untransformed intact plants. Moreoverde novobiosynthesis of sengosterone is suggested in the roots ofA. bracteosa.

Acaricidal activity of compounds from Cinnamomum camphora (L.) Presl against the carmine spider mite, Tetranychus cinnabarinus

BACKGROUND

Tetranychus cinnabarinus (Boisduval) is one of the most important, highly polyphagous pests of a wide range of field and greenhouse crops throughout the world. The control of this mite is still based primarily on the use of synthetic chemical pesticides. In this study, we screened eight plant extracts from China and evaluated the natural compounds showing acaricidal properties from the plant extract, considering their potential use as an alternative to synthetic pesticides.

RESULTS

In bioassay screening assays, the Cinnamomum camphora (L.) Presl extract showed significantly greater acaricidal activity against T. cinnabarinus than the other seven plant extracts tested. Five compounds were identified from the C. camphora extract via repeated column chromatography and gas chromatography-mass spectrometry analysis. All the compounds presented acaricidal activity, with 2,4-di-tert-butylphenol and ethyl oleate exhibiting the greatest activity. At 7 days after treatment in a potted seedling experiment, the LC50 values of 2,4-di-tert-butylphenol and ethyl oleate were found to be 1850.94 and 2481.65 mg kg(-1) respectively. Microscopic observations showed that the mites displayed the symptomology of poisoning.

CONCLUSION

These results demonstrated that the C. camphora extract and its two active components show the potential to be developed as new natural acaricides for controlling carmine spider mites.

Bioefficacy of crude extract of Cyperus aromaticus (Family: Cyperaceae) cultured cells, against Aedes aegypti and Aedes albopictus mosquitoes

OBJECTIVE

To evaluate the growth inhibition activity of the crude extract of Cyperus aromaticus (C. aromaticus) cultured cells against the 3rd instar larvae of Aedes aegypti (Linn.) and Aedes albopictus Skuse (Ae. albopictus) under laboratory conditions, and determine the sublethal effects (EI50) of the crude extract of C. aromaticus cultured cells on some biological and morphological parameters of both Aedes mosquito species during two generations as well.

METHODS

The cell suspension cultures of C. aromaticus were activated from five callus lines (P4, Pa, Z1, Z6 and Ml) derived from the root explants of in vitro plantlets. The cultured cells were extracted in chloroform and used as plant material for the present study. For detection of juvenile hormone III, the crude extracts were analyzed by HPLC. Then the crude extracts of the three C. aromaticus cultured cell lines which contained varied amounts of juvenile hormone III [high level (P4 cell line), medium level (Z1 cell line) and low level (Ml cell line)] were tested against Aedes mosquito species. Laboratory evaluation was performed against late third instar larvae of the Vector Control Research Unit strains of Ae. aegypti and Ae. albopictus using the standard WHO method. The effects of EI50 of the C. aromaticus cultured P4 cells on fecundity, fertility, growth period, sex ratio, adult size and longevity of Aedes mosquitoes were assessed.

RESULTS

Bioassay tests presented the remarkable growth inhibition activity of the crude extracts of C. aromaticus cultured cells against the two Aedes mosquitoes. Between the two mosquito species, Ae. albopictus was more susceptible to the crude extracts with lower EI50 values. EI50 of the crude extract of C. aromaticus cultured cells (P4) increased the sterility indices in the parental generation females in both Aedes mosquito species. A significant delay in the pupal formation and adult emergence were observed in the parental generation of the both mosquito species. The sex ratio of the adult population either parental or F1 generation of the Aedes mosquito species was not significantly affected by the EI50 dosage of the crude extract of C. aromaticus cultured P4 cells. A significant decrease in the wing length of the treated adult (female and male) of Aedes aegypti as well as the treated female of Ae. albopictus were observed. Longevity of the adult female of the parental generation of both Aedes mosquitoes as well as females of F1 generation of Ae. albopictus were significantly decreased.

CONCLUSIONS

The present study revealed the potential of the crude extract of C. aromaticus cultured cells in controlling vector mosquito populations in the effort to reduce the transmission of vector borne diseases.