Response of Epilachna paenulata to two flavonoids, pinocembrin and quercetin, in a comparative study

Field screening and identification of biochemical indices of pod borer (Helicoverpa armigera) resistance in chickpea mutants

Chickpea pod borer (CPB) (Helicoverpa armigera) is one of the major pests, causing significant yield losses. The objectives were to screen chickpea mutants for pod borer resistance/tolerance under field conditions and identification of biochemical markers of tolerance. Chickpea mutant CM216-A/15 had highest leaf (25 trichomes/mm2) and stem trichome density (17 trichomes/mm2) with least pod damage at Kallur Kot and highest pod weight per plant (22.8 ± 2.6g) at AZRI. Higher total phenolic contents (TPCs) and antioxidant capacity were detected in tolerant mutants, i.e., CM216-A/15 and CM664/15. TPC was positively associated with pod yield and had negative correlation with pod damage. Mutants CM216-A/15, CM664/15, and CM766/15 depicted the highest resilience to CPB, owing to higher hairiness, better antioxidant defense response, and lower levels of hydrolytic enzymes and sugars. Identified biochemical markers like TPC, total oxidant status, superoxide dismutase, and pigments can be used for screening of CPB-tolerant/resistant mutants.

Flavonoids as Insecticides in Crop Protection-A Review of Current Research and Future Prospects

Pesticide overuse in agricultural systems has resulted in the development of pest resistance, the impoverishment of soil microbiota, water pollution, and several human health issues. Nonetheless, farmers still depend heavily on these agrochemicals for economically viable production, given the high frequency at which crops are affected by pests. Phytopathogenic insects are considered the most destructive pests on crops. Botanical pesticides have gained attention as potential biopesticides and complements to traditional pesticides, owing to their biodegradability and low toxicity. Plant-based extracts are abundant in a wide variety of bioactive compounds, such as flavonoids, a class of polyphenols that have been extensively studied for this purpose because of their involvement in plant defense responses. The present review offers a comprehensive review of current research on the potential of flavonoids as insecticides for crop protection, addressing the modes and possible mechanisms of action underlying their bioactivity. The structure-activity relationship is also discussed. It also addresses challenges associated with their application in pest and disease management and suggests alternatives to overcome these issues.

Quercetin stimulates an accelerated burst of oviposition-based reproductive strategy in codling moth controlled by juvenile hormone signaling pathway

The advantageous characteristics of invasive pests, particularly their ability to reproduce and adapt to the environment, have been observed. However, it remains unclear what specific inherent superiority enables fruit pests to successfully invade and dominate in interactions with other species. In this study, we report that Cydia pomonella (Linnaeus), a notorious invasive pest of pome fruits and walnuts globally, employs unique reproductive strategies in response to quercetin, a plant compound in host fruits. By monitoring adult dynamics and fruit infestation rates, we observed a competitive relationship between C. pomonella and the native species Grapholita molesta (Busck). C. pomonella was able to occupy vacant niches to ensure its population growth. We also found that quercetin had different effects on the reproductive capacity and population growth of C. pomonella and G. molesta. While quercetin stimulated the fecundity and population growth of G. molesta, it inhibited C. pomonella. However, C. pomonella was able to rapidly increase its population after exposure to quercetin by adopting an 'accelerated burst' of oviposition strategy, with each individual making a greater reproductive contribution compared to the control. We further demonstrated that the effect of quercetin on oviposition is regulated by the juvenile hormone (JH) signaling pathway in C. pomonella, allowing it to prioritize survival. The enhanced reproductive fitness of G. molesta in response to quercetin is attributed to the regulation of JH titers and key genes such as Met and Kr-h1, which in turn up-regulate reproduction-related genes Vg and VgR. In contrast, C. pomonella is inhibited. These findings shed light on the mechanisms interspecific competition and help to improve our understanding of the global spread of C. pomonella, which can be attributed to its inherent superiority in terms of reproductive strategy.

Nutrient enrichment promotes invasion success of alien plants via increased growth and suppression of chemical defenses

In support of the prediction of the enemy release hypothesis regarding a growth-defense trade-off, invasive alien plants often exhibit greater growth and lower anti-herbivory defenses than native plants. However, it remains unclear how nutrient enrichment of invaded habitats may influence competitive interactions between invasive alien and co-occurring native plants, as well as production of anti-herbivore defense compounds, growth-promoting hormones, and defense-regulating hormones by the two groups of plants. Here, we tested whether: (i) nutrient enrichment causes invasive alien plants to produce greater biomass and lower concentrations of the defense compounds flavonoids and tannins than native plants; and (ii) invasive alien plants produce lower concentrations of a defense-regulating hormone jasmonic acid (JA) and higher concentrations of a growth-promoting hormone gibberellic acid (GA3). In a greenhouse experiment, we grew five congeneric pairs of invasive alien and native plant species under two levels each of nutrient enrichment (low vs. high), simulated herbivory (leaf clipping vs. no-clipping), and competition (alone vs. competition) in 2.5-L pots. In the absence of competition, high-nutrient treatment induced a greater increase in total biomass of invasive alien species than that of native species, whereas the reverse was true under competition as native species benefitted more from nutrient enrichment than invasive alien species. Moreover, high-nutrient treatment caused a greater increase in total biomass of invasive alien species than that of native species in the presence of simulated herbivory. Competition induced higher production of flavonoids and tannins. Simulated herbivory induced higher flavonoid expression in invasive alien plants under low-nutrient than high-nutrient treatments. However, flavonoid concentrations of native plants did not change under nutrient enrichment and simulated herbivory treatments. Invasive alien plants produced higher concentrations of GA3 than native plants. Taken together, these results suggest that impact of nutrient enrichment on growth of invasive alien and co-occurring native plants may depend on the level of competition that they experience. Moreover, invasive alien plants might adjust their flavonoid-based defense more efficiently than native plants in response to variation in soil nutrient availability and herbivory pressure. Our findings suggest that large-scale efforts to reduce nutrient enrichment of invaded habitats may help to control future invasiveness of target alien plant species.

Invasive Plants Have Higher Resistance to Native Generalist Herbivores Than Exotic Noninvasive Congeners

Research on the invasive plant Phytolacca americana (L.) mostly focuses on its medicinal value and enrichment of heavy metals. However, little is known regarding its impact on native herbivorous insects. In this study, we explored the effects of P. americana and the exotic noninvasive Phytolacca icosandra (L.) on the Spodoptera litura (Fabricius) (native tobacco cutworm) via bioassay, oviposition preference, detoxifying enzyme activity analysis, and phytochemical determination. We found that the oviposition preference index (OPI) of S. litura feeding on P. icosandra was higher than that of P. americana. The developmental duration of S. litura feeding on P. icosandra was shorter than that of P. americana. Additionally, the Acetylcholinesterase (AchE) and Glutathione-S-transferase (GST) activities of S. litura feeding on P. americana were higher than that of S. litura feeding on artificial diets or P. icosandra. The content of lignin and flavonoids in P. americana was relatively high, whereas starch content was relatively low. These findings suggest invasive plants have higher resistance to herbivores, thereby suffering less damage than exotic noninvasive plants.

Sorghum in foods: Functionality and potential in innovative products

Sorghum grain is a staple food for about 500 million people in 30 countries in Africa and Asia. Despite this contribution to global food production, most of the world's sorghum grain, and nearly all in Western countries, is used as animal feed. A combination of the increasingly important ability of sorghum crops to resist heat and drought, the limited history of the use of sorghum in Western foods, and the excellent functional properties of sorghum grain in healthy diets, suggests a greater focus on the development of new sorghum-based foods. An understanding of the structural and functional properties of sorghum grain to develop processes for production of new sorghum-based foods is required. In this review, we discuss the potential of sorghum in new food products, including sorghum grain composition, the functional properties of sorghum in foods, processing of sorghum-based products, the digestibility of sorghum protein and starch compared to other grains, and the health benefits of sorghum. In the potential for sorghum as a major ingredient in new foods, we suggest that the gluten-free status of sorghum is of relatively minor importance compared to the functionality of the slowly digested starch and the health benefits of the phenolic compounds present.

Flavonoids Are Intra- and Inter-Kingdom Modulator Signals

Flavonoids are a broad class of secondary metabolites with multifaceted functionalities for plant homeostasis and are involved in facing both biotic and abiotic stresses to sustain plant growth and health. Furthermore, they were discovered as mediators of plant networking with the surrounding environment, showing a surprising ability to perform as signaling compounds for a multitrophic inter-kingdom level of communication that influences the plant host at the phytobiome scale. Flavonoids orchestrate plant-neighboring plant allelopathic interactions, recruit beneficial bacteria and mycorrhizal fungi, counteract pathogen outbreak, influence soil microbiome and affect plant physiology to improve its resilience to fluctuating environmental conditions. This review focuses on the diversified spectrum of flavonoid functions in plants under a variety of stresses in the modulation of plant morphogenesis in response to environmental clues, as well as their role as inter-kingdom signaling molecules with micro- and macroorganisms. Regarding the latter, the review addresses flavonoids as key phytochemicals in the human diet, considering their abundance in fruits and edible plants. Recent evidence highlights their role as nutraceuticals, probiotics and as promising new drugs for the treatment of several pathologies.

Repellence or attraction: secondary metabolites in pepper mediate attraction and defense against Spodoptera litura

BACKGROUND

Resistance to insect pests is an important self-defense characteristic of pepper plants. However, the resistance of different pepper cultivars to Spodoptera litura larvae, one of the main insect pest species on pepper, is not well understood.

RESULTS

Among seven pepper cultivars evaluated, cayenne pepper 'FXBX' showed the highest repellency to third instar S. litura larvae, Chao tian chili pepper 'BLTY2' showed the lowest repellency. Plant volatiles (1-hexene, hexanal, β-ionone, (E,E)-2,6-nonadienal, and methyl salicylate) affected host selection by S. litura. Among these, 1-hexene, hexanal, and β-ionone at concentrations naturally-released by pepper leaves were found to repel S. litura. Interestingly, S. litura larvae fed on the larva-attracting pepper cultivar, (BLTY2) had an extended developmental period, which was about 13 days longer than larvae fed on FXBX. Besides, the survival rate of larvae fed on BLTY2 was 22.5 ± 0.0%, indicating that the leaves of BLTY2 can kill S. litura larvae. Correlation analysis showed that larval survival rate, emergence rate, female adult longevity, and pupal weight were positively correlated with the vitamin C, amino acids, protein, cellulose, and soluble sugar contents, but were negatively correlated with wax and flavonoids contents.

CONCLUSION

We identified two different modes of direct defense exhibited by pepper cultivars against S. litura. One involves the release of repellent volatiles to avoid been fed on (FXBX cultivar). The other involves the inhibition of the growth and development or the direct killing of S. litura larvae which feeds on it (BLTY2 cultivar). © 2022 Society of Chemical Industry.

Antifeeding and Oviposition Deterrent Effect of Ludwigia spp. (Onagraceae) against Plutella xylostella (Lepidoptera: Plutellidae)

Plants produce a wide variety of bioactive compounds with insecticidal properties, such as secondary metabolites capable of interfering with the nutrition and reproduction of pest species such as Plutella xylostella. Thus, the objective of this study was to evaluate the effects of aqueous and ethanolic extracts of Ludwigia spp. (Onagraceae) on the feeding and oviposition of P. xylostella. Choice bioassays were performed using aqueous and ethanolic extracts. The aqueous extract of L. tomentosa resulted in an approximately 81% reduction in larval feeding compared to that in the control, with an antifeedant index (AI) of 52%. The aqueous and ethanolic extract of L. nervosa acted by stimulating larval feeding. The oviposition was significantly reduced in the kale leaves treated with aqueous and ethanolic extracts of Ludwigia spp. The aqueous extracts promoted an average 90% reduction in oviposition when compared to that in the control, and an oviposition deterrent index (ODI) above 61% was classified as an oviposition deterrent. In addition, ethanolic extracts affected 81% of oviposition, with an ODI above 41%. Bioassays should be performed to clarify the use of aqueous and ethanolic extracts of L. nervosa as they acted as phagostimulants in the feeding tests and as deterrents in the oviposition tests. The phenolic compounds-flavonoids, condensed tannins, and alkaloids-were more abundant in L. nervosa, L. tomentosa, L. sericea, and L. longifolia. The extracts of L. longifolia and L. tomentosa showed the best results, interfering with the host choice for feeding and oviposition in P. xylostella and representing an alternative for the control of diamondback moths.

Anti-trypanosomal screening of Salvadoran flora

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, and in Central America, it is considered one of the four most infectious diseases. This study aimed to screen the anti-trypanosomal activity of plant species from Salvadoran flora. Plants were selected through literature search for plants ethnobotanically used for antiparasitic and Chagas disease symptomatology, and reported in Museo de Historia Natural de El Salvador (MUHNES) database. T. cruzi was incubated for 72 h with 2 different concentrations of methanolic extracts of 38 species, among which four species, Piper jacquemontianum, Piper lacunosum, Trichilia havanensis, and Peperomia pseudopereskiifolia, showed the activity (≤ 52.0% viability) at 100 µg/mL. Separation of the methanolic extract of aerial parts from Piper jacquemontianum afforded a new flavanone (4) and four known compounds, 2,2-dimethyl-6-carboxymethoxychroman-4-one (1), 2,2-dimethyl-6-carboxychroman-4-one (2), cardamomin (3), and pinocembrin (5), among which cardamomin exhibited the highest anti-trypanosomal activity (IC₅₀ = 66 µM). Detailed analyses of the spectral data revealed that the new compound 4, named as jaqueflavanone A, was a derivative of pinocembrin having a prenylated benzoate moiety at the 8-position of the A ring.

Domestication of Plants of Ugni molinae Turcz (Myrtaceae) Interferes in the Biology of Chilesia rudis (Lepidoptera: Erebidae) Larvae

In terms of the domestication process in murtilla, studies have found changes in the concentration of phenolic compounds, with reduction of chemical defense of plants, depending on the change in the feeding behavior of insects. Thus, we hypothesized that the domestication of Ugni molinae decreases the content of phenolic compounds and modifies the feeding preference of Chilesia rudis larvae. Leaves of three parental ecotypes and four cultivated ecotypes were used in preference experiments to evaluate the mass gain and leaves consumption of larvae. Phenolic extracts from leaves of U. molinae were analyzed by HPLC. Identified compounds were incorporated in an artificial diet to assess their effect on mass gain, consumption, and survival of the larvae. The presence of phenolic compounds in bodies and feces was also evaluated. In terms of choice assays, larvae preferred parental ecotypes. Regarding compounds, vanillin was the most varied between the ecotypes in leaves. However, plant domestication did not show a reduction in phenolic compound concentration of the ecotypes studied. Furthermore, there was no clear relation between phenolic compounds and the performance of C. rudis larvae. Whether this was because of sequestration of some compounds by larvae is unknown. Finally, results of this study could also suggest that studied phenolic compounds have no role in the C. rudis larvae resistance in this stage of murtilla domestication process.

Nitrogen Supply Alters Rice Defense Against the Striped Stem Borer Chilo suppressalis

Plant nutrition status is closely associated with plant defense against insect herbivores. However, the way nitrogen supply regulates rice anti-herbivore is not clear. This study investigated the effects of low (LN, 0.3 mM) and high (HN, 3 mM) nitrate levels on rice resistance against the striped stem borer Chilo suppressalis (SSB), one of the major destructive rice pests. Seven-day-old rice seedlings were cultured with different nitrate levels for 30 days and then inoculated with third instars of SSB. LN significantly enhanced rice anti-herbivore defense and lowered the total nitrogen content in the plants, but increased the content of free amino acids after SSB infestation. Additionally, LN significantly increased the accumulation of phenolic acids and flavonoids, especially lignin, resulting in enhanced constitutive defense in SSB-infested plants. SSB feeding led to a rapid accumulation of secondary metabolites. HN application led to the accumulation of metabolites derived from cinnamic acid, p-coumaric acid, p-coumaric CoA, feruloyl CoA, and apigenin, while LN led to the accumulation of metabolites derived from 3-dehydroquinic acid, phenylalanine, acetyl CoA, and aspartic acid. Collectively, our finding suggests that nitrogen deficiency enhances rice anti-herbivore defense via constitutive defense by the accumulation of phenolic acids and flavonoids.

Phytochemical Screening and Bioactivity of Ludwigia spp. in the Control of Plutella xylostella (Lepidoptera: Plutellidae)

Simple Summary

Ludwigia species have several pharmacological applications, but their insecticidal proprieties have not been tested. This research thus aimed to study the effects of aqueous extracts on the biological characteristics of Plutella xylostella. We noted that the L. tomentosa, L. longifolia and L. sericea extracts were active. These species showed the best results regarding their ability to control P. xylostella populations, due to the presence of substances that inhibit food consumption and interfere in the morphological and physiological transformations of the offspring and adult oviposition.

Abstract

We tested the bioactivity of aqueous extracts of Ludwigia spp. (Myrtales: Onagraceae) on the biological cycle of Plutella xylostella. We assessed the duration of and viability during the larval, pupal and adult phases, as well as the influence of the extracts on the fecundity and hatching of P. xylostella eggs. Subsequently, we phytochemically screened the extracts. The extracts of L. tomentosa and L. longifolia reduced the pupal weight instead of prolonging the larval stage of P. xylostella. The L. tomentosa effect caused higher larval mortality and reduced the fecundity and hatching of P. xylostella eggs, and L. sericea reduced the egg survival. The phenolic compounds—flavonoids, condensed tannins and alkaloids—were more abundant in L. nervosa, L. tomentosa, L. sericea and L. longifolia. The L. tomentosa, L. longifolia and L. sericea extracts were bioactive, and these species showed the best results regarding their ability to control P. xylostella populations, because these plants produce substances able to inhibit food consumption and interfere with the morphological and physiological transformations of the offspring and the oviposition of adults.

Molecular docking analyses of CYP450 monooxygenases of Tribolium castaneum (Herbst) reveal synergism of quercetin with paraoxon and tetraethyl pyrophosphate: in vivo and in silico studies

Pest management in stored grain industry is a global issue due to the development of insecticide resistance in stored grain insect pests. Excessive use of insecticides at higher doses poses a serious threat of food contamination and residual toxicity for grain consumers. Since the development of new pesticide incurs heavy costs, identifying an effective synergist can provide a ready and economical tool for controlling resistant pest populations. Therefore, the synergistic property of quercetin with paraoxon and tetraethyl pyrophosphate has been evaluated against the larvae and adults of Tribolium castaneum (Herbst). Comparative molecular docking analyses were carried out to further identify the possible mechanism of synergism. It was observed that quercetin has no insecticidal when applied at the rate of 1.5 and 3.0 mg/g; however, a considerable synergism was observed when applied in combination with paraoxon. The comparative molecular docking analyses of CYP450 monooxygenase (CYP15A1, CYP6BR1, CYP6BK2, CYP6BK3) family were performed with quercetin, paraoxon and tetraethyl pyrophosphate which revealed considerable molecular interactions, predicting the inhibition of CYP450 isoenzyme by all three ligands. The study concludes that quercetin may be an effective synergist for organophosphate pesticides depending upon the dose and type of the compound. In addition, in silico analyses of the structurally diversified organophosphates can effectively differentiate the organophosphates which are synergistic with quercetin.

Application of ultrasonic-assisted inclusion complex formation with α-cyclodextrin for simultaneous spectrophotometric determination of gallic acid and vanillic acids in fruit samples

There are various methodologies to generate second-order data. Spectrophotometric method owing to its high sensitivity continues to be of wide interest to analytical chemists. Spectra recording at different interval time while the reaction is proceeded, or at different pHs, or at different concentrations of complexing agent are examples of strategies by which one can generate second-order data by the spectrophotometric method. In this work, for the first time, we employed α-CD as an inclusion complexing agent under ultrasonic irradiation for simultaneous determination of gallic acid (GA) and vanillic acid (VA). UV spectra of a mixture of two analytes were recorded as a function of α-CD concentration. A calibration set containing 9 reference samples was used to construct model using bilinear least squares/residual bilinearization (BLLS/RBL) as second-order calibration method. The predictive ability of the resulting model was validated by a test set including 5 samples. Finally, the proposed model was successfully applied to simultaneously determine the content of GA and VA in five fruit juice samples. Satisfactory results in terms of the recovery yields were obtained. In a word, UV-spectroscopy coupled with a strategy to yield a second-order data in combination to second-order calibration methods has high potential to be a simple, quick and accurate analysis procedure for the determination of various types of chemical structures in practice.

Biochemical composition and antioxidant activity affected by spraying potassium sulfate in black grape (Vitis vinifera L. cv. Rasha)

BACKGROUND

The physiological and metabolic processes involved with grapevine growth and production are influenced by key macro- and micronutrients. Potassium is an essential plant nutrient that affects growth and fruit quality. In this study, the impact of foliar spraying of potassium sulfate (K₂ SO₄ ) on qualitative characteristics of grape berries was evaluated in the cultivar 'Rasha', a commonly cultivated cultivar in Kurdistan province of Iran. Leaves of the fully grown vines were sprayed with each of the 1.5 and 3 g L^-1 K₂ SO₄ solutions once (1 month after petal senescence) and twice (15 days after first spraying). The control plants were sprayed with distilled water. Various biochemical contents and enzyme activities on the ripe berries were analyzed.

RESULTS

Significant increases in anthocyanin, total protein content, and antioxidant enzyme activities were observed in the berries treated twice with 3 g L^-1 K₂ SO₄ . Concentrations of total carbohydrate, phenol, and antioxidant activity in berries sprayed with K₂ SO₄ were higher than in the controls. We observed a strong correlation between antioxidant activity and different phenolic compounds.

CONCLUSION

These findings suggest that K₂ SO₄ treatment influences biosynthesis of phenolic compounds and antioxidant enzymes. Thus, treatment by K₂ SO₄ could improve nutritional and qualitative attributes of grape. © 2018 Society of Chemical Industry.

Utilization of Quercetin as an Oviposition Stimulant by Lab-Cultured Coleomegillamaculata in the Presence of Conspecifics and a Tissue Substrate

Background: The discovery of natural products to improve the reproductive performance of mass-reared predators is an important aim for successful augmentative biological control. We tested the hypothesis that quercetin (a bioflavonoid) stimulates oviposition by the ladybird beetle Coleomegillamaculata in the presence of conspecifics and a tissue substrate. Methods: We conducted bioassays in solitary cages (housing one female) and communal cages (housing 10 females) to estimate daily oviposition site preferences, egg production in response to quercetin in the presence or absence of a tissue paper substrate, and female “resting” positions. Results: Females preferentially oviposited within 1–2 cm of quercetin powder, held in a tiny dish, at the base of cages. When given a choice, females oviposited in the dish with quercetin over a tissue paper substrate. In one of two experiments, they produced more egg clutches, regardless of oviposition site, when the quercetin and tissue were in close juxtaposition. Females “rested” on the tissue in the presence or absence of quercetin. Conclusion: This study provides evidence that quercetin can be utilized as an oviposition stimulant by C. maculata in a rearing system. Future research should determine if quercetin stimulates oviposition in other ladybird beetle species.

Insecticidal effects of Vernonanthura nebularum against two economically important pest insects

Vernonanthura nebularum (Cabrera) H. Rob. (Asteraceae), an endemic species from the north of Argentina, is a rich source of elephantopus-type sesquiterpene lactones. These compounds have proved to be promising antiparasitic agents, but there is no report about their action against pest insects. In this work we studied for the first time the antifeedant and toxic effects of V. nebularum natural products against the fall army warm Spodoptera frugiperda Smith and the oviposition deterrent activity against the fruit fly Ceratitis capitata Wiedemann. As a result, we found that extracts, fractions composed of sesquiterpene lactones and pure sesquiterpene lactones altered larval feeding behavior in the food choice test. Nutritional parameters of S. frugiperda larvae were also affected. Fraction II (300 μg/g of diet.), containing compounds 1, 2 and 3, was the most toxic substance with 80% pupal mortality and wing malformations in adults. In oviposition deterrent experiments against Ceratitis capitata, we observed a moderate effect at 30 μg/cm² of the test compound. The most active substances were the methanolic extract, dichloromethane subextract and lactone 2. According to our results, V. nebularum natural products could be used for maximizing the effectiveness and specificity in future insecticide design with specific or multiple target sites, while ensuring the economic and ecological sustainability, in addition to combat the increasing resistance rates developed by synthetic pesticides.

Chemical Compounds and Bioactivity of Aqueous Extracts of Alibertia spp. in the Control of Plutella xylostella L. (Lepidoptera: Plutellidae)

Successive applications of insecticides to control Plutella xylostella L. (Lepidoptera: Plutellidae) have resulted in the emergence of resistant populations of this insect. A novel control measure for this target insect could be the use of botanical insecticides derived from plant tissues. Hence, we experimentally tested aqueous extracts of Alibertia edulis (Rich.), Alibertia intermedia (Mart.), and Alibertia sessilis (Vell.) K. Schum. found in the Brazilian savannah in order to investigate their potential to disrupt the life cycle of P. xylostella. Aqueous extracts of the leaves of A. intermedia and A. sessilis negatively affected the development of P. xylostella in all stages of the life cycle, prolonging the larval stage and causing mortality in the larval or pupal stages. Treatments with A. intermedia and A. sessilis extracts caused the lowest fecundity and the number of hatched larvae. The harmful effects of these aqueous extracts on the life cycle of P. xylostella may be attributable to the flavonoids and other phenolic compounds present in A. intermedia and A. sessilis. These aqueous botanical extracts are low in toxicity when compared to non-aqueous pesticides, and may emerge as an effective approach for control of populations of P. xylostella.

Plant Flavonoid Content Modified by Domestication

Plant domestication can modify and weaken defensive chemical traits, reducing chemical defenses in plants and consequently their resistance against pests. We characterized and quantified the major defensive flavonols and isoflavonoids present in both wild and cultivated murtilla plants (Ugni molinae Turcz), established in a common garden. We examined their effects on the larvae of Chilesia rudis (Butler) (Lepidoptera: Arctiidae). Insect community and diversity indices were also evaluated. We hypothesized that domestication reduces flavonoid contents and modifies C. rudis preference, the insect community, and diversity. Methanolic extracts were obtained from leaves of U. molinae plants and analyzed by high performance liquid chromatography. Results showed higher insect numbers (86.48%) and damage index (1.72 ± 0.16) in cultivated plants. Four new first records of insects were found associated with U. molinae. Diversity indices, such as Simpson, Shannon, and Margalef, were higher in cultivated plants than in wild plants. Furthermore, eight isoflavonoids were identified in U. molinae leaves for the first time. The five flavonols showed higher concentrations in wild U. molinae leaves (89.8 µg/g) than in cultivated plants (75.2 µg/g); however, no differences were found in isoflavonoids between wild and cultivated plants. The larvae of C. rudis consumed more leaf material of cultivated plants than wild plants in choice (3.8 vs. 0.8 mm2) and no-choice (7.5 vs. 3.0 mm2) assays. Our study demonstrates that domestication in U. molinae reduces the amount of flavonoids in leaves, increasing the preference of C. rudis and the insect community.

Feeding-induced phenol production in Capsicum annuum L. influences Spodoptera litura F. larval growth and physiology

We studied the role of induced plant phenols as a defense response to insect herbivory. Phenolic compounds were induced in Capsicum annuum L., the source of many culinary peppers, after feeding by different stages of the insect pest, Spodoptera litura F. The phenols were identified and quantified using high performance liquid chromatography (HPLC) and effects produced by these phenols on larval development were studied. Vanillic acid was identified in plants challenged by second, fourth, and fifth instar larvae, but not in plants challenged by third instar nor unchallenged plants. Syringic acid production was induced in chili plants infested with second (0.429 ± 0.003 μg/g fresh weight, fourth (0.396 ± 0.01 μg/g fresh weight), and fifth instar (5.5 ± 0.06 μg/g fresh weight) larvae, compared to untreated plants (0.303 ± 0.01 μg/g fresh weight) plants. Leaves surface treated with the rutin deterred oviposition. Dietary exposure to chlorogenic acid, vanillic acid, syringic acid, sinapic acid, and rutin led to enhanced activities of detoxifying enzymes, β-glucosidase, carboxyl esterase, glutathione S-transferase, and glutathione reductase in the midgut tissues of all the larval instars, indicating the toxic nature of these compounds. Protein carbonyl content and acetylcholinesterase activity was analyzed to appreciate the role of induced plant phenols in insect protein oxidation and terminating nerve impulses.

Chemical Constituents of Supercritical Extracts from Alpinia officinarum and the Feeding Deterrent Activity against Tribolium castaneum

Alpinia officinarum has been confirmed to possess bioactivities against some pests. In this work, a sample was obtained from A. officinarum rhizomes by supercritical fluid CO₂ extraction (SFE). According to GC-MS analysis, the main chemical components for SFE-sample included benzylacetone (26.77%), 1,7-diphenyl-5-hydroxy-3-heptanone (17.78%), guaiacylacetone (10.03%) and benzenepropanal (7.42%). The essential oil of A. officinarum rhizomes (LD₅₀ = 20.71 μg/adult) exhibited more contact toxicity than SFE extract (LD₅₀ = 82.72 μg/adult) against Tribolium castaneum. From SFE extracts, one new compound, 1-phenyl-4-(16,17-dimethyl-9,13-octadiene)-5-isopentenyl-7-(4"-methoxyl-3"-hydroxyl-phenyl)-3-heptanone (3), together with five known compounds identified as 5-hydroxy-1,7-diphenyl-3-heptanone (1), 1,7-diphenyl-4-hepten-3-one (2), galangin (4), galangin-3-methyl ether (5) and pinocembrin (6), were isolated and their feeding deterrent activities against T. castaneum adults were assessed. It was found that compounds 1-6 had feeding deterrent activities against T. castaneum with feeding deterrent indices of 18.21%, 18.94%, 19.79%, 26.99%, 20.34%, and 35.81%, respectively, at the concentration of 1500 ppm. Hence, the essential oil and SFE extracts/compounds of A. officinarum rhizomes represent promising alternatives in the control of T. castaneum adults.

Plant genotypes affect aboveground and belowground herbivore interactions by changing chemical defense

Spatially separated aboveground (AG) and belowground (BG) herbivores are closely linked through shared host plants, and both patterns of AG-BG interactions and plant responses may vary among plant genotypes. We subjected invasive (USA) and native (China) genotypes of tallow tree (Triadica sebifera) to herbivory by the AG specialist leaf-rolling weevil Heterapoderopsis bicallosicollis and/or the root-feeding larvae of flea beetle Bikasha collaris. We measured leaf damage and leaves rolled by weevils, quantified beetle survival, and analyzed flavonoid and tannin concentrations in leaves and roots. AG and BG herbivores formed negative feedbacks on both native and invasive genotypes. Leaf damage by weevils and the number of beetle larvae emerging as adults were higher on invasive genotypes. Beetles reduced weevil damage and weevils reduced beetle larval emergence more strongly for invasive genotypes. Invasive genotypes had lower leaf and root tannins than native genotypes. BG beetles decreased leaf tannins of native genotypes but increased root tannins of invasive genotypes. AG herbivory increased root flavonoids of invasive genotypes while BG herbivory decreased leaf flavonoids. Invasive genotypes had lower AG and BG herbivore resistance, and negative AG-BG herbivore feedbacks were much stronger for invasive genotypes. Lower tannin concentrations explained overall better AG and BG herbivore performances on invasive genotypes. However, changes in tannins and flavonoids affected AG and BG herbivores differently. These results suggest that divergent selection on chemical production in invasive plants may be critical in regulating herbivore performances and novel AG and BG herbivore communities in new environments.

Insecticidal Properties of a Highly Potent Wax Isolated from Dolichandra cynanchoides Cham

Bioassay-guided fractionation of an ethanolic extract of the aerial parts of Dolichandra cynanchoides Cham. (Bignoniaceae) led to the isolation of a natural wax with anti-insect activity against Spodoptera frugiperda (Noctuidae) and Epilachna paenulata (Coleptera). The compound was identified spectroscopically as an ester of a C27 fatty acid and a C25 alcohol, pentacosyl heptacosanoate (1). The effective doses of 1 for 50% feeding inhibition (ED50) of S. frugiperda and E. paenulata were 0.82 and 8.53 µg/cm², respectively, in a choice test, while azadirachtin showed ED50 of 0.10 and 0.59 µg/cm², respectively. In a no-choice test, both insects refused to feed on leaves treated with 1 at doses of 0.1 µg/cm² or greater inhibiting larval growth and dramatically reducing survival. The lethal doses 50 (LD50) of 1 were 0.39 and 0.68 µg/cm² for S. frugiperda and E. paenulata, respectively. These results indicate that 1 has potential for development as botanical insecticides. Similar esters might be obtainable in large quantities as many edible crops produce wax esters that are discarded during food processing. Research on these materials could lead to the detection of similar waxes with insecticidal activity.

PHYSIOLOGICAL EFFECTS OF RESVERATROL AND COUMARIC ACID ON TWO MAJOR GROUNDNUT PESTS AND THEIR EGG PARASITOID BEHAVIOR

Groundnut, Arachis hypogea L., is one of the plant species that synthesizes phenolic compounds, resveratrol and coumaric acid. They are induced as a defense strategy in plant in response to feeding lepidopterans. The present study investigated the role of resveratrol and coumaric acid in producing antiherbivore effects as a direct defense against two major groundnut pests, Spodoptera litura F. and Amsacta albistriga W., and in indirect defense by attracting the egg parasitoid Trichogramma chilonis Ishii under laboratory conditions. The phenolic compounds deterred the feeding of both pests and caused reduction in the larval weights in a dose-dependent manner in leaf disk bioassays. Antioxidant mechanisms of larvae fed with these phenols were measured by estimating the activities of superoxide dismutase (SOD), ascorbate peroxidase (APOX), and catalase (CAT). Enzyme activities increased significantly in experimental larvae, more so in resveratrol-treated than in coumaric acid treated larvae. Feeding larvae with resveratrol and coumaric acid resulted in enhanced activities of detoxifying enzymes, carboxyl esterase (EST), and glutathione-S-transferase (GST) in the midgut tissues of both species, indicating the toxic nature of these compounds. Trichogramma chilonis was more attracted toward coumaric acid treatments in Y-olfactometer tests than to resveratrol. This study contributes to the understanding of the roles of resveratrol and coumaric acid in direct as well as indirect defense, we infer a possible utilization of these compounds in alternate measures of groundnut pest control in future.

New environmentally-friendly antimicrobials and biocides from Andean and Mexican biodiversity

Persistent application of pesticides often leads to accumulation in the environment and to the development of resistance in various organisms. These chemicals frequently degrade slowly and have the potential to bio-accumulate across the food chain and in top predators. Cancer and neuronal damage at genomic and proteomic levels have been linked to exposure to pesticides in humans. These negative effects encourage search for new sources of biopesticides that are more "environmentally-friendly" to the environment and human health. Many plant or fungal compounds have significant biological activity associated with the presence of secondary metabolites. Plant biotechnology and new molecular methods offer ways to understand regulation and to improve production of secondary metabolites of interest. Naturally occurring crop protection chemicals offer new approaches for pest management by providing new sources of biologically active natural products with biodegradability, low mammalian toxicity and environmentally-friendly qualities. Latin America is one of the world's most biodiverse regions and provide a previously unsuspected reservoir of new and potentially useful molecules. Phytochemicals from a number of families of plants and fungi from the southern Andes and from Mexico have now been evaluated. Andean basidiomycetes are also a great source of scientifically new compounds that are interesting and potentially useful. Use of biopesticides is an important component of integrated pest management (IPM) and can improve the risks and benefits of production of many crops all over the world.

Insect Antifeedant Potential of Xanthohumol, Isoxanthohumol, and Their Derivatives

Xanthohumol (14) and isoxanthohumol (6) derived from hop (Humulus lupulus L., Cannabaceae) and selected chalcone and chromene derivatives, obtained by chemical synthesis, were studied for antifeedant activity against the peach-potato aphid (Myzus persicae [Sulz.]). The study used also commercially available 4-chromanone (1), flavanone (4), naringenin (5), chromone (7), flavone (8), 7-aminoflavone (9), trans-chalcone (10), and 4-methoxychalcone (12). For chromone derivatives it was observed that the presence of a phenyl substituent at C-2 in the chromone (7) skeleton increased the insect antifeedant activity, and this activity was observed for a longer time. Also, the introduction of an amino group at C-7 of flavone (8) considerably increased the insect antifeedant activity, which was observed for the whole test time. Among the compounds examined, the strongest deterrents were isoxanthohumol (6), 7-methoxy-2,2-dimethylchroman-4-one (3), 7-aminoflavone (9), and 4-ethyl-4'-methoxychalcone (13).

Domestication in Murtilla (Ugni molinae) Reduced Defensive Flavonol Levels but Increased Resistance Against a Native Herbivorous Insect

Plant domestication can have negative consequences for defensive traits against herbivores, potentially reducing the levels of chemical defenses in plants and consequently their resistance against herbivores. We characterized and quantified the defensive flavonols from multiple cultivated ecotypes with wild ancestors of murtilla, Ugni molinae Turcz, an endemic plant from Chile, at different times of the year, and examined their effects on a native insect herbivore, Chilesia rudis Butler (Lepidoptera: Arctiidae). We hypothesized that domestication results in a decrease in flavonol levels in U. molinae plants, and that this negatively affected C. rudis performance and preference. Ethanolic extracts were made from leaves, stems, and fruit of murtilla plants for flavonol analysis. Flavonols identified were kaempferol, quercetin, rutin, and quercetin 3-D-β-glucoside, the last two being the most abundant. More interestingly, we showed differences in flavonol composition between wild and cultivated U. molinae that persisted for most of the year. Relative amounts of all four flavonols were higher in wild U. molinae leaves; however, no differences were found in the stem and fruit between wild and cultivated plants. In choice and no-choice assays, C. rudis larvae gained more mass on, and consumed more leaf material of, wild as compared with cultivated U. molinae plants. Moreover, when applied to leaves, larvae ate more leaf material with increasing concentrations of each flavonol compound. Our study demonstrates that domestication in U. molinae reduced the amount of flavonols in leaves as well as the performance and preference of C. rudis, indicating that these compounds stimulate feeding of C. rudis.

Drought enhances folivory by shifting foliar metabolomes in Quercus ilex trees

At the molecular level, folivory activity on plants has mainly been related to the foliar concentrations of nitrogen (N) and/or particular metabolites. We studied the responses of different nutrients and the whole metabolome of Quercus ilex to seasonal changes and to moderate field experimental conditions of drought, and how this drought may affect folivory activity, using stoichiometric and metabolomic techniques. Foliar potassium (K) concentrations increased in summer and consequently led to higher foliar K : phosphorus (P) and lower carbon (C) : K and N : K ratios. Foliar N : P ratios were not lowest in spring as expected by the growth rate hypothesis. Trees exposed to moderate drought presented higher concentrations of total sugars and phenolics and these trees also experienced more severe folivory attack. The foliar increases in K, sugars and antioxidant concentrations in summer, the driest Mediterranean season, indicated enhanced osmoprotection under natural drought conditions. Trees under moderate drought also presented higher concentrations of sugars and phenolics; a plant response to avoid water loss. These shifts in metabolism produced an indirect relationship between increased drought and folivory activity.

Phytotoxicity of secondary metabolites isolated from Flourensia oolepis S.F.Blake

The aim of this study was to isolate the active principles of Flourensia oolepis S.F.Blake (Asteraceae), which completely inhibited the germination of Raphanus sativus seeds at 10 mg/ml. Flavanone pinocembrin and sesquiterpene ilicol, were isolated by bioassay-guided fractionation. They were active both against monocot and dicot seeds. Pinocembrin was the most active compound, with an IC50 (germination) value of 0.24, 3.40, 3.28, and 3.55 mM against Panicum miliaceum, Avena sativa, Lactuca sativa, and R. sativus, respectively; ilicol, however, exhibited IC50 (germination) values of 0.67, 2.73, 5.25, and 9.66 mM for the same species, respectively. Pinocembrin and ilicol inhibited root growth and showed IC50 (root growth) values of 0.199, 14.68, 8.05, 7.69 mM, and 1.22, 2.90, 7.35, 8.07 mM, against P. miliaceum, A. sativa, L. sativa, and R. sativus, respectively. Pinocembrin and ilicol reduced Allium cepa cell division without chromosome aberrations.

Effect of Hadda beetle, Epilachna vigintioctopunctata Fab. (Coleoptera: Coccinellidae) infestation on eggplant leaf (Solanum melongena L.) and bio-control potential of essential oil formulations

The present study evaluates the nature of feeding damage of Epilachna vigintioctopunctata on leaves of Solanum melongena L. and antifeedant activities of essential oil formulations against E. vigintioctopunctata. Investigations were made on the morphological and anatomical damage caused by the feeding activity of the adults and grubs of E. vigintioctopunctata. Adult E. vigintioctopunctata scraped the green matter of the upper and lower sides of the leaves of Solanum melongena leaving behind only a network of veins. This characteristic scraping made the leaves papery and the infested eggplants exhibited inter venal damage or holes on the leaves. The reduction percentage of leaf fresh weight and leaf dry weight in infested leaves after one generation were 11.4 and 15.2%, respectively. In the grub infested leaves of eggplant, fully damaged epidermis, parenchyma cells and phloem cells of vascular bundles were observed. The total mean percentage of infested leaf damage was 12.75 +/- 0.43%. Maximum antifeedant activities of 80.06, 61.92% were observed in oil formulation III and formulation I, respectively at 100 ppm concentration against the fourth instars grub of E. vigintioctopunctata. This would be a good alternative for the chemical pesticides.

Techniques for analysis of plant phenolic compounds

Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

Herbal extracts and phytochemicals: plant secondary metabolites and the enhancement of human brain function

Humans consume a wide range of foods, drugs, and dietary supplements that are derived from plants and which modify the functioning of the central nervous sytem (CNS). The psychoactive properties of these substances are attributable to the presence of plant secondary metabolites, chemicals that are not required for the immediate survival of the plant but which are synthesized to increase the fitness of the plant to survive by allowing it to interact with its environment, including pathogens and herbivorous and symbiotic insects. In many cases, the effects of these phytochemicals on the human CNS might be linked either to their ecological roles in the life of the plant or to molecular and biochemical similarities in the biology of plants and higher animals. This review assesses the current evidence for the efficacy of a range of readily available plant-based extracts and chemicals that may improve brain function and which have attracted sufficient research in this regard to reach a conclusion as to their potential effectiveness as nootropics. Many of these candidate phytochemicals/extracts can be grouped by the chemical nature of their potentially active secondary metabolite constituents into alkaloids (caffeine, nicotine), terpenes (ginkgo, ginseng, valerian, Melissa officinalis, sage), and phenolic compounds (curcumin, resveratrol, epigallocatechin-3-gallate, Hypericum perforatum, soy isoflavones). They are discussed in terms of how an increased understanding of the relationship between their ecological roles and CNS effects might further the field of natural, phytochemical drug discovery.