Toxic and antifeedant activities of prenylated flavonoids isolated from Tephrosia apollinea L. against three major coleopteran pests of stored grains with reference to their structure-activity relationship

Phytochemistry and pharmacology of natural prenylated flavonoids

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

Heterozygous frameshift mutation in FaMYB10 is responsible for the natural formation of red and white-fleshed strawberry (Fragaria x ananassa Duch)

During natural evolution and artificial selection, the fruit color of many species has been repeatedly gained or lost and is generally associated with mutations in genes encoding R2R3-MYB transcription factors, especially MYB10. In this study, we show that a heterozygous frameshift mutation (FaMYB10^AG-insert/FaMYB10^wild ) is responsible for the loss of anthocyanins in the flesh of cultivated strawberry. Comparative transcriptomic and metabolomic analyses of red- and white-fleshed strawberry indicated that the low expression level of FaUFGT (flavonol-O-glucosyltransferases) was responsible for the loss of anthocyanins and accumulation of proanthocyanidin in the white-fleshed strawberry and was the crucial gene that encodes enzymes of the anthocyanin biosynthesis pathway. Accordingly, overexpression and silencing of FaUFGT altered anthocyanin content and changed the flesh color of strawberry fruits. Furthermore, whole-genome resequencing analyses identified an AG insertion in the FaMYB10 coding region (FaMYB10^AG-insert ) of white-fleshed strawberry. Y1H and EMSA assays showed that FaMYB10^wild was able to bind to the promoter of the FaUFGT gene, while the FaMYB10^AG-insert could not. The skin and flesh color were tightly linked to the number of fully functional FaMYB10 copies in the selfing progeny of white-fleshed strawberry. Our results suggested that heterozygous frameshift mutation of FaMYB10 resulted in the loss of the ability to activate the expression of the FaUFGT gene, was responsible for the natural formation of red and white-fleshed strawberry.

Flavonoids as biopesticides - Systematic assessment of sources, structures, activities and environmental fate

Biopesticides obtained from renewable resources and associated with biodegradability have the potential to address resource limitations and environmental pollution, often caused by many conventional pesticides, due to the facility of natural products to run in natural nutrient cycles. Flavonoids are considered benign substitutes for pesticides, however, little comprehensive information of their pesticidal activities and critical evaluation of their associated advantages is available. Therefore, this systematic review assessed sources, structures, activities and the environmental fate of flavonoids on a basis of 201 selected publications. We identified 281 different flavonoids that were investigated for their pesticidal activity as either a pure compound or a flavonoid-containing extract, with quercetin, kaempferol, apigenin, luteolin and their glycosides as the most studied compounds. Agricultural or food waste, a potential sustainable source for flavonoids, represent 10.6% of the plant sources of flavonoids within these studies, showing the currently underutilization of these preferable feedstocks. Analysis of pesticidal activities and target organisms revealed a broad target spectrum for the class of flavonoids, including fungi, insects, plants, bacteria, algae, nematodes, molluscs and barnacles. Little information is available on the environmental fate and biodegradation of flavonoids, and a connection to studies investigating pesticidal activities is largely missing. Emerging from these findings is the need for comprehensive understanding of flavonoids pesticidal activities with emphasis on structural features that influence activity and target specificity to avoid risks for non-target organisms. Only if the target spectrum and environmental fate of a potential biopesticide are known it can serve as a benign substitute. Then, flavonoids can be integrated in a valorization process of agricultural and food waste shifting the extract-produce-consume linear chain to a more circular economy.

A Cotton Lignin Biosynthesis Gene, GhLAC4, Fine-Tuned by ghr-miR397 Modulates Plant Resistance Against Verticillium dahliae

Plant lignin is a component of the cell wall, and plays important roles in the transport potential of water and mineral nutrition and plant defence against biotic stresses. Therefore, it is necessary to identify lignin biosynthesis-related genes and dissect their functions and underlying mechanisms. Here, we characterised a cotton LAC, GhLAC4, which participates in lignin biosynthesis and plant resistance against Verticillium dahliae. According to degradome sequencing and GUS reporter analysis, ghr-miR397 was identified to directedly cleave the GhLAC4 transcript through base complementary. GhLAC4 knockdown and ghr-miR397 overexpression significantly reduced basal lignin content compared to the control, whereas ghr-miR397 silencing significantly increased basal lignin levels. Based on staining patterns and GC/MS analysis, GhLAC4 acted in G-lignin biosynthesis. Under V. dahliae infection, we found that G-lignin content in ghr-miR397-knockdowned plants significantly increased, compared to these plants under the mock treatment, while G-lignin contents in GhLAC4-silenced plants and ghr-miR397-overexpressed plants treated with pathogen were comparable with these plants treated with mock, indicating that GhLAC4 participates in defence-induced G-lignin biosynthesis in the cell wall. Knockdown of ghr-miR397 in plants inoculated with V. dahliae promoted lignin accumulation and increased plant resistance. The overexpression of ghr-miR397 and knockdown of GhLAC4 reduced lignin content and showed higher susceptibility of plants to the fungal infection compared to the control. The extract-free stems of ghr-miR397-knockdowned plants lost significantly less weight when treated with commercial cellulase and V. dahliae secretion compared to the control, while the stems of ghr-miR397-overexpressed and GhLAC4-silenced plants showed significantly higher loss of weight. These results suggest that lignin protects plant cell walls from degradation mediated by cellulase or fungal secretions. In summary, the ghr-miR397-GhLAC4 module regulates both basal lignin and defence-induced lignin biosynthesis and increases plant resistance against infection by V. dahliae.

Chemical composition, insecticidal and biochemical effects of two plant oils and their major fractions against Aedes aegypti, the common vector of dengue fever

In an attempt to reduce the massive application of the toxic chemical pesticides, essential oils (EOs) of Achillea biebersteinii and Juniperus procera were obtained through hydrodistillation and analyzed using (GC–FID) and (GC–MS). α-terpinene and p-cymene were detected as the major components in the EO of A. biebersteinii, while eugenol and ß-caryophyllene were the major constituents in the EO of J. procera. The plant EOs and major fractions act as considerable mosquitocides against Aedes aegypti L, the common transmitter of Dengue fever. The EOs and major fractions were tested at 6.25, 12.5, 25, 50 and 100 μl/l. Insect mortality was time and dose-dependent, and the adult stage was more sensitive than larvae. At a concentration of 50 μl/l, 24 post treatment larval and adult mortality ranged between (40.3 and 89.3%) and (51.4 and 95.6%), respectively. The LC₅₀ values ranged between 12.2 and 70.1 μl/l against larvae and between 10.1 and 63.12 μl/l against adults. All of the crude EOs were more potent than their major fractions. Eugenol and ß-caryophyllene showed strong mosquitocidal activity than p-cymene and α-terpinene. The corrected percentage mortality was increased over time with all of the test materials. In terms of lethal time required to kill 50% of the population (LT₅₀), a concentration of 100 μl/l of J. procera EO showed LT₅₀ values of 2.3 and 1.7 h against larvae and adult, respectively. The EOs induced considerable inhibition of acetylcholinesterase activity, where J. procera crude oil (IC₅₀ = 13.12mM) and eugenol (IC₅₀ = 19.65mM) were the most potent. Results proved that the test plant oils and their major fractions could be developed as natural pest control agents to control A. aegypti.

A chalcone (Pongamol) and phytoconstituents of Tephrosia purpurea

Tephrosia purpurea stem extract fractions shows more amount of Cyclohexane, 1-ethenyl-1-methyl-2,4-bis(1-methylethenyl)-, (1α,2β,4β)- (62.32%). Secondary metabolites contents were higher in stem than root of T. purpurea. It is the first time a chalcone (Pongamol) was crystallised from the column chromatography fraction of T. purpurea stem extract identified by using FT-IR and XRD. Quantitative analysis of T. purpurea stem and root reveals that total saponins, tannins and phenols (mg/g plant powder) contents were higher in the former than the latter part of the plant, respectively.

Flavonoids in Agriculture: Chemistry and Roles in, Biotic and Abiotic Stress Responses, and Microbial Associations

The current world of climate change, global warming and a constantly changing environment have made life very stressful for living entities, which has driven the evolution of biochemical processes to cope with stressed environmental and ecological conditions. As climate change conditions continue to develop, we anticipate more frequent occurrences of abiotic stresses such as drought, high temperature and salinity. Living plants, which are sessile beings, are more exposed to environmental extremes. However, plants are equipped with biosynthetic machinery operating to supply thousands of bio-compounds required for maintaining internal homeostasis. In addition to chemical coordination within a plant, these compounds have the potential to assist plants in tolerating, resisting and escaping biotic and abiotic stresses generated by the external environment. Among certain biosynthates, flavonoids are an important example of these stress mitigators. Flavonoids are secondary metabolites and biostimulants; they play a key role in plant growth by inducing resistance against certain biotic and abiotic stresses. In addition, the function of flavonoids as signal compounds to communicate with rhizosphere microbes is indispensable. In this review, the significance of flavonoids as biostimulants, stress mitigators, mediators of allelopathy and signaling compounds is discussed. The chemical nature and biosynthetic pathway of flavonoid production are also highlighted.

Tephrosia apollinea seed: a new rich source of essential polyunsaturated fatty acids, tocopherols, sterols, and squalene

Tephrosia apollinea is a legume species, native to southwest Asia and northeast Africa, rich in bioactive flavonoids (hydrophilic compounds). T. apollinea seeds were not considered previously as a potential source of lipophilic compounds such as: essential fatty acids, tocopherols, sterols, and squalene, hence, the present study were performed. The oil yield in T. apollinea seeds amounted to 11.8% dw. The T. apollinea seed oil was predominated by the polyunsaturated fatty acids - linoleic (26.8%) and α-linolenic (22.7%). High levels were recorded also for oleic (27.6%) and palmitic (14.9%) acids. Four tocopherols and one tocotrienol, with the domination of γ-tocopherol (98%) were identified in T. apollinea seed oil. The β-sitosterol (59%), Δ5-stigmasterol (21%) and campesterol (9%) were detected as main sterols in T. apollinea seed oil. The total content of tocochromanols, sterols, carotenoids and squalene in the T. apollinea seed oil was 256.7, 338.1, 12.5 and 1103.8 mg/100 g oil, respectively. T. apollinea seeds oil, due to the high concentration of lipophilic bioactive compounds can find a potential application in the food, cosmetic and pharmaceutical industry.

Medicinally active principles analysis of Tephrosia apollinea (Delile) DC. growing in the United Arab Emirates

Background

Tephrosia apollinea is a leguminous plant and is native to southwest Asia, Arabia, northwestern India and northeast Africa. In traditional system, it is used for medicinal and coloring purpose. The present study aims to explore the phytochemical, proximate analysis, element contents and antioxidant potential of T. apollinea extract.

Methods

The phytochemical screening was done with qualitative methods. Proximate analysis and elemental composition were performed from powdered sample. In vitro antioxidant assays such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and reducing power-scavenging assays were used for evaluating the antioxidant properties.

Results

Qualitative screening of methanolic extract of T. apollinea showed the presence of alkaloids, phenolics, flavonoids, terpenoids, glycosides and saponins. The methanolic extract of T. apollinea exhibited a significant dose dependent inhibition of DPPH activity, with a 50% inhibition (IC⁵⁰) at a concentration found to be 29.41 µg/ml, which was compared with standard GAE (IC⁵⁰ = 31.09 μg/ml). The reducing power shows good linear relationship in both standard gallic acid (R² = 0.956) and T. apollinea extract (0.984).

Conclusions

The results of our study clearly suggested that the methanolic extract of T. apollinea may serve as potential source of natural antioxidant for nutraceutical application.

Two novel prenylated kaempferol derivatives from fresh bud's fur of Platanus acerifolia and their anti-proliferative activities

Two novel prenylated kaempferol derivatives (1, 2), together with seven known metabolites were isolated from ethanol extract of fresh Platanus acerifolia bud's fur by multistep chromatographic processing. Structure of compounds 1 and 2 was confirmed by 1D, 2D NMR spectra and HR-ESI-MS. In addition, compound 1 was further analysed by X-ray crystallography. Anti-proliferative activities in vitro against human breast carcinoma (MCF-7) and human hepatocellular carcinoma (Hep-G2) cell lines for compound 1, 2 and 8 were evaluated. Compound 1 exhibited cytotoxic activity towards MCF-7 and Hep-G2 cell lines with the IC₅₀ values 38.2 and 39.5 μM, respectively. Moreover, compound 2 showed weak cytotoxic activities against the two cell lines.

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).