Isolation of Bioactive Compounds from Sunflower Leaves (Helianthus annuus L.) Extracted with Supercritical Carbon Dioxide

An Integrated ANN-PRA/DP4+ Tandem Computational Approach Contributing to the Ordering of the Heliannuol Family

Heliannuols are a unique class of sesquiterpenes isolated mostly from Helianthus annuus, commonly known as sunflower. The interesting allelopathic properties, combined with their unprecedented carbon skeletons, have drawn wide attention to phytochemistry and synthetic groups. So far, 14 heliannuols (heliannuols A-N) have been described in the literature, although some of them have not yet been validated by total synthesis. Moreover, the structural proposal of some compounds was based on the similarity of NMR data reported for previously isolated analogues (which in many instances turned out to be incorrect), coupled with little or no stereochemical analysis. Consequently, the structural reassignment is a recurring theme in heliannuol's family. Through a rigorous and comprehensive quantum chemical simulation of NMR parameters, encompassing an integrated ANN-PRA/DP4+ tandem approach, we intended to advance unexplored directions regarding the structure of the entire heliannuol family. Furthermore, we found that the size of the fused ring significantly influences the signals corresponding to the aromatic ring, making this discovery an excellent diagnostic tool for quickly determining the core structure of these compounds.

New and Antifungal Diterpenoids of Sunflower against Gray Mold

Sunflower (Helianthus annuus L.) is cultivated around the world as an oil crop, and its receptacle is the byproduct and is usually deemed to be an agro-industrial waste. Then, phytochemical constituents and antifungal bioactivity of the sunflower receptacle against phytopathogenic fungi were investigated. As a result, 17 diterpenoids including 4 new compounds were isolated, and most of them showed potential antifungal activity against Botrytis cinerea, in which compounds 1, 3, 5, and 15 exhibited better inhibitory effect with the minimum inhibitory concentration values of 0.05-0.1 mg/mL. Meanwhile, four antifungal diterpenoids destructed plasma membrane integrity, suspended the biofilm formation ability, and increased the extravasation of cellular contents of B. cinerea. Moreover, the EtOAc extract of sunflower receptacle could keep 42.9% of blueberries from the invasion of B. cinerea at 1.6 mg/mL. The finding suggested that sunflower receptacle might be a biocontrol agent for preventing fruit from postharvest diseases.

The Allelopathic Activity of Aqueous Extracts of Helianthus annuus L., Grown in Boreal Conditions, on Germination, Development, and Physiological Indices of Pisum sativum L

Evaluation of the allelopathy relationship between different crops is a sensible strategy fallowing the correct use of positive effects and to avoid the disadvantageous effects among plants. This study aimed to detect the allelopathic effect of aqueous extracts of sunflower (Helianthus annuus L.), grown in a boreal climatic zone, on the growth, subsequent development, and physiological traits of pea (Pisum sativum L.). Three factors have been studied: donor plant fertilization (unfertilized and fertilized), aqueous extracts from donor plant organs (leaves and stems (L+S), heads (H) and roots (R)); four concentrations of extracts (0%, 25%, 50% and 75%). The aqueous extracts from fertilized sunflower donor plant at 25% and 50% concentration acted as potential biostimulants that stimulated pea seed germination (SG), whereas L+S and R extracts at 75% concentration from unfertilized donor plant inhibited SG, at 4 days after sowing. The aqueous extracts demonstrated a stimulating effect on above-ground and root dry mass, compared to the control. The concentration of extracts demonstrated a significant inhibitory effect on SPAD. R extract revealed the strongest allelopathic effect on physiological traits of pea. L+S and H extracts at 25% concentration had stimulating effects, while 50% and 75% concentrations showed inhibiting effects on the photosynthetic rate. The water use efficiency, stomatal conductance, and stomatal limitation were inhibited, whereas, the transpiration rate, photosynthetic water use efficiency and intercellular CO₂ concentration were stimulated, with an increasing of extract concentrations, comparatively to the control.

Oral administration of Helianthus annuus leaf extract ameliorates atopic dermatitis by modulation of T cell activity in vivo

BACKGROUND

Atopic dermatitis (AD) is multifactorial disease that is highly involved in the activity of T cells from the skin lesion. Seeds of Helianthus annuus extract have been traditionally used as anti-inflammatory reagent but few studies have been reported on leaf of H. annuus that are discarded uselessly as an immunomodulator.

PURPOSE

Therefore, here, the regulatory effect of Helianthus annuus extract (HAE) on AD via suppression of T cell activity was investigated.

METHODS

The efficacy of HAE was evaluated in T cells stimulated with CD3/CD28 antibody and PMA/A23187. And demonstration of the alleviating effect of HAE on AD in the ears of Balb/c female mice stimulated with mite extract and DNCB.

RESULTS

Pre-treatment with HAE abrogates IL-2 production from activated T cells. It was also found that HAE suppresses the expression of surface molecules in activated T cells. Cell viability results demonstrated that HAE is not associated with cytotoxicity in resting and activated T cells. Besides, we exhibited that regulated phosphorylation of MAPK through TAK1-IKKα-NFκB by pre-treatment with HAE leads to the suppressive effect of HAE on T cell activation. Oral administration of HAE attenuates manifestations of AD including reduced thickness of dermis and epidermis, decreased IgE level in serum, and declined mRNA levels of atopic cytokines on ear tissues. The ameliorative effect of HAE on AD was found to be associated with suppressed activity of T cells from draining lymph nodes.

CONCLUSION

Therefore, our results provide that HAE alleviates AD symptoms via modulation of T cell activity. In addition, these results suggest the immunomodulatory effect of HAE on T-cell mediated diseases.

Transition Metal Catalyzed Hiyama Cross-Coupling: Recent Methodology Developments and Synthetic Applications

Hiyama cross-coupling is a versatile reaction in synthetic organic chemistry for the construction of carbon-carbon bonds. It involves the coupling of organosilicons with organic halides using transition metal catalysts in good yields and high enantioselectivities. In recent years, hectic progress has been made by researchers toward the synthesis of diversified natural products and pharmaceutical drugs using the Hiyama coupling reaction. This review emphasizes the recent synthetic developments and applications of Hiyama cross-coupling.

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.

Revisiting the structure of Heliannuol L: A computational approach

Recently, structural elucidation of natural products has undergone a revolution. The combined use of different modern spectroscopic methods has allowed obtaining a complete structural assignment of natural products using small amounts of sample. However, despite the extraordinary ongoing advances in spectroscopy, the mischaracterization of natural products has been and remains a recurrent problem, especially when the substance presents several stereogenic centers. The misinterpretation of nuclear magnetic resonance (NMR) data has resulted in frequent reports addressing structural reassignment. In this context, a great effort has been devoted to developing quantum chemical calculations that simulate NMR parameters accurately, allowing to achieve a more precise spectral interpretation. In this work, we employed a protocol for theoretical calculations of ¹ H NMR chemical shifts and coupling constants using density functional theory (DFT), followed by the application of the DP4+ method to revisit the structure of Heliannuol L, a member of the Heliannuol class, isolated from Helianthus annuus. Our results indicate that the originally proposed structure of Heliannuol L needs a stereochemical reassignment, placing the hydroxyl bonded to C10 in the opposite side of the methyl and hydroxyl groups bonded to C7 and C8, respectively.

The use of alternative food sources to improve health and guarantee access and food intake

To feed and provide Food Security to all people in the world is a big challenge to be achieved with the 2030 Agenda. Undernutrition and obesity are to the opposite of a healthy nutritional status. Both conditions are associated with unbalanced nutrition, absence of food or excess of non-nutritive foods intake. These two nutritional conditions associated with food production are closely related to some goals highlighted by the United Nations in the 2030 Agenda to achieve sustainable world development. In this context, the search for alternative foods whose sustainable production and high nutritional quality guarantee regular access to food for the population must be encouraged. Alternative foods can contribute to Food Security in many ways as they contribute to the local economy and income generation. Popularizing and demystifying the uses of unconventional food plants, ancestral grains, flowers, meliponiculture products, and edible insects as sources of nutrients and non-nutrients is another challenge. Herein, we present an overview of alternative foods - some of them cultivated mostly in Brazil - that can be explored as sources of nutrients to fight hunger and malnutrition, improve food production and the economic growth of nations.

Bioactive Diterpenes from the Brazilian Native Plant (Moquiniastrum pulchrum) and Their Application in Weed Control

Even today, weeds continue to be a considerable problem for agriculture. The application of synthetic herbicides produces serious environmental consequences, and crops suffer loss of their activity due to the appearance of new resistant weed biotypes. Our aim is to develop new effective natural herbicides that improve the problem of resistance and do not harm the environment. This work is focused on a bioassay-guided isolation and the characterization of natural products present in Moquiniastrum pulchrum leaves with phytotoxic activity and its preliminary application in weeds. Moquiniastrum pulchrum was selected for two reasons: it is an abundant species in the Cerrado region (the second most important ecosystem in Brazil, after the Amazon)—the explanation behind its being a dominant species is a major focus of interest—and it has traditional employment in folk medicine. Six major compounds were isolated in this plant: one flavone and five diterpenes, two of which are described for the first time in the literature. Four of the six compounds exhibited phytotoxic activity in the bioassays performed. The results confirmed the phytotoxic potential of this plant, which had not been investigated until now.

Insights into the Supercritical CO2 Extraction of Perilla Oil and Its Theoretical Solubility

In the current research, the supercritical carbon dioxide (SCCO2) procedure was used to extract volatile oils from perilla leaves. The yields of the volatile oils and the four main constituents, limonene, perillaldehyde, β-caryophyllene, and (Z,E)-α-farnesene obtained by the SCCO2 procedure were 1.31-, 1.12-, 1.04-, 1.05-, and 1.07-fold higher than those obtained by the hydrodistillation technique, respectively. Furthermore, the duration and temperature of extraction were 40 min and 45 °C lower, respectively, in the former procedure compared to the latter technique. These advantages reveal that SCCO2 not only obtains high-quality extracts, but also meets the requirements of green environmental protection. The theoretical solubilities of the volatile oils acquired by the SCCO2 dynamic extraction at various temperatures and pressures were 1.385 × 10−3–8.971 × 10−3 (g oil/g CO2). Moreover, the three density-based models were well correlated with these theoretical solubility data, with a high coefficient of determination and low average absolute relative deviation.

Heliannuol: Distribution, Biological Activities, 1H and 13C-NMR Spectral Data

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Heliannuols are an important class of compounds isolated from Helianthus annuus, a common sunflower, with allelopathic properties. Interestingly, two of these fourteen compounds have been isolated from a gorgonian, Pseudopterogorgia rigida. This review compiles data on the isolation and biological activity of heliannuols described in the literature and briefly reports the papers describing their syntheses. This review could stimulate research into other natural species and syntheses. Further, it describes the 1H and 13C-NMR spectral data described in the literature for the 14 heliannuols already isolated and correlates them with their respective structures. Therefore, we believe that these searchable data enable a rapid identification in routine analysis of the crude extracts of sunflowers or gorgonians.

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry.

Phytotoxic Diterpenoids from Plants and Microorganisms

Phytotoxic natural products with either unique or various structures are one of the most abundant sources for the discovery of potential allelochemicals, natural herbicides, and plant growth regulators. Phytotoxic diterpenoids, a relatively large class of natural products, play an important role in the plant-plant or plant-microorganism interactions. This article argues that the phytotoxic diterpenoids isolated from the plants and microorganisms can either inhibit the seed germination and the growth of plant seedlings or lead to some disease symptoms on the tested plant tissues and plant seedlings.

Crystal Structures and Cytotoxicity of ent-Kaurane-Type Diterpenoids from Two Aspilia Species

A phytochemical investigation of the roots of Aspilia plurisetaled to the isolation of ent-kaurane-type diterpenoids and additional phytochemicals (1⁻23). The structures of the isolated compounds were elucidated based on Nuclear Magnetic Resonance (NMR) spectroscopic and mass spectrometric analyses. The absolute configurations of seven of the ent-kaurane-type diterpenoids (3⁻6, 6b, 7 and 8) were determined by single crystal X-ray diffraction studies. Eleven of the compounds were also isolated from the roots and the aerial parts of Aspilia mossambicensis. The literature NMR assignments for compounds 1 and 5 were revised. In a cytotoxicity assay, 12α-methoxy-ent-kaur-9(11),16-dien-19-oic acid (1) (IC₅₀ = 27.3 ± 1.9 µM) and 9β-hydroxy-15α-angeloyloxy-ent-kaur-16-en-19-oic acid (3) (IC₅₀ = 24.7 ± 2.8 µM) were the most cytotoxic against the hepatocellular carcinoma (Hep-G2) cell line, while 15α-angeloyloxy-16β,17-epoxy-ent-kauran-19-oic acid (5) (IC₅₀ = 30.7 ± 1.7 µM) was the most cytotoxic against adenocarcinomic human alveolar basal epithelial (A549) cells.

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

Several Hiyama cross-coupling reactions of oxasilacycloalkenes and aryl iodides are described that produce trisubstituted Z-styrenes in moderate to excellent yields. Both electron-rich and electron-poor aryl iodides are tolerated in the cross-coupling reaction. The oxasilacycloalkene coupling partners were prepared by ruthenium-catalyzed intramolecular anti-hydrosilylation of alkynols. One of the cross-coupling products was converted to a 1-benzoxocane, albeit in low yield, using an intramolecular Buchwald–Hartwig etherification. The cyclic ether produced contains the carbon skeleton of heliannuol A.

Production of oridonin-rich extracts from Rabdosia rubescens using hyphenated ultrasound-assisted supercritical carbon dioxide extraction

BACKGROUND

Among active components in Rabdosia rubescens, oridonin has been considered a key component and the most valuable compound because it has a wide range of activities beneficial to human health. To produce a high-quality oridonin extract, an alternative hyphenated procedure involving an ultrasound-assisted and supercritical carbon dioxide (HSC-CO₂ ) extraction method to extract oridonin from R. rubescens was developed in this study. Fictitious solubilities of oridonin in supercritical CO₂ (SC-CO₂ ) with ultrasound assistance were measured by using the dynamic method at temperatures ranging from 305.15 K to 342.15 K over a pressure range of 11.5 to 33.5 MPa.

RESULTS

Fictitious solubilities of oridonin at different temperatures and pressures were over the range of 2.13 × 10^-6 to 10.09 × 10^-6 (mole fraction) and correlated well with the density-based models, including the Bartle model, the Chrastil model, the Kumar and Johnston model and the Mendez-Santiago and Teja model, with overall average absolute relative deviations (AARDs) of 6.29%, 4.39%, 3.12% and 5.07%, respectively.

CONCLUSION

Oridonin exhibits retrograde solubility behaviour in the supercritical state. Fictitious solubility data were further determined and obtained a good fit with four semi-empirical models. Simultaneously, the values of the total heat of solution, vaporisation and solvation of oridonin were estimated. © 2016 Society of Chemical Industry.

Base-Promoted Formal [4 + 3] Annulation between 2-Fluorophenylacetylenes and Ketones: A Route to Benzoxepines

The first base-promoted formal [4 + 3] annulation between 2-fluorophenylacetylenes and ketones has been disclosed. The reaction proceeds through a tandem α-vinylation of ketones followed by an intramolecular nucleophilic aromatic substitution (SNAr) reaction of the in situ generated β,γ-unsaturated ketone intermediates, providing a straightforward access to a wide range of functionalized benzoxepines in moderate to high yields. The transition-metal-free methodology featured a wide substrate scope, the use of easily available starting materials, and a high functional group tolerance.

Helikaurolides A-D with a Diterpene-Sesquiterpene Skeleton from Supercritical Fluid Extracts of Helianthus annuus L. var. Arianna

Four novel compounds (1-4) with an unprecedented skeleton that combines a sesquiterpene lactone and a kaurane diterpene acid were isolated from Helianthus annuus L. var. Arianna extract, which was obtained under supercritical conditions. The structures of 1-4 were elucidated by NMR and MS analyses. The biosynthetic routes involve sesquiterpene lactones and kauranic acid, both of which were previously isolated from this species.