Microwave-Assisted Extraction of Ricinine from Ricinus communis Leaves

The alkaloid ricinine (3-cyano-4-methoxy-N-methyl-2-pyridone) is found in di erent parts of the Ricinus communis plant and is known to possess several bioactive properties, including strong antioxidant activity. In this study, a new microwave-assisted extraction (MAE) method was developed for the recovery of ricinine from R. communis leaves. The extraction variables studied were extraction temperature (between 125 C and 175 C), microwave power (between 500Wand 1000 W), extraction time (between 5 min and 15 min), extraction solvent (between 10% and 90% of EtOAc in MeOH), and solvent-to-sample ratio (between 25:1 mL and 50:1 mL of solvent per gram of the sample). On studying the e ects of extraction variables, both solvent and liquid-to-solid ratio were found to exhibit the highest e ects on ricinine recovery. A fast (15 min) microwave-assisted extraction method was developed (high temperatures can be applied because the stability of ricinine is proven in the literature), allowing for the recovery of ricinine from R. communis leaves. The study revealed that R. communis leaves had almost 1.5 mg g1 (dried weight) of ricinine

Sesquiterpene lactones enriched-fractions obtained from Cynara cardunculus extract diaultrafiltration

Sesquiterpene lactones (SL) are allelopathic compounds that demonstrate great potential of use in sustainable weed management. In this study, membrane processing technology was used for ethanolic Cynara cardunculus leaves extract (CcLE) ultra- and nanofiltration to produce SL-enriched fractions with increased phytotoxic activity. Experiments were conducted to select an ultrafiltration membrane (DuraMem500, DuraMem900 and SuezGH2000) for SL recovery and high molecular weight compounds (MWC) removal. SuezGH2000, which had rejection percentage of 50 % and 88 % for cynaropicrin (Cyn) and chlorophyll, respectively, was used for a sequential purification along with DuraMem200 for lower MWC removal. Since Cyn content on initial feed (11.9 %) and permeate (11.2 %) were similar, as well as phytotoxic activity, the results suggested that DuraMem200 was unsuitable for CcLE fractionation. SuezGH2000 revealed a slight increase on SL content, so, the permeation profile and enhancement of SL content were evaluated. An increase on SL content (36.0–71.0 %) was obtained after 2.3 diavolumes, followed by a decrease between 2.6 and 4.7 diavolumes. Phytotoxic activity evaluations revealed a direct association with SL content with enhancement of activity, particularly at inhibiting shoot growth of Portulaca oleracea. This study revealed SuezGH2000 effectiveness on SL purity improvement on CcLE fractions after 2.3 diavolumes and its potential to be used as a bioherbicide active component

Optimized Ultrasound-Assisted Extraction of Psidium laruotteanum Roots: A Concentrated Source of Piceid from the Brazilian Savanna

Psidium laruotteanum is a subshrub Myrtaceae, native to the Brazilian savanna, and distributed in Central and South America. Here, the health beneficial compound piceid (reservatrol-3-β-mono-d-glucoside) is described for the first time in the genus Psidium. The ultrasound-assisted extraction from P. laruotteanum roots was optimized by a response surface methodology. A central composite design was used to assess six extraction variables. Optimal extractions were obtained with 62.5% MeOH in water at 69.1 °C, amplitude of 70%, cycle of 0.5 s−1, pH 5.7 and solvent–solid ratio of 40:1, for 10 min. The method showed excellent recovery (90%–95%) and precision (CV: 0.69% for repeatability and 0.43% for intermediate precision). This species appears as the most concentrated plant source of piceid reported to date (29.15 mg·g−1 in dry roots). Additionally, a very fast extraction (5 min) can afford 96% recovery of piceid from Psidium laruotteanum roots. It could be used as a natural and cheap source of piceid for several applications

Sunflower Metabolites Involved in Resistance Mechanisms against Broomrape

Several strategies have been proposed to control parasitic plants and these include biological control, the use of herbicides, and suicidal germination or trap crops. In the case of sunflower, the most effective solution is genetic resistance. Nevertheless, the use of resistant cultivars is followed by the appearance of new and more virulent races of the parasite that overcome the existing sources of resistance. For this reason, it is necessary to increase our knowledge of the mechanisms involved in the resistant varieties. In this study, the presence of compounds involved in pre-attachment resistance mechanisms in sunflower varieties was analyzed. The production of stimulators of the germination of parasitic plant seeds and the concentration of the haustorial elongation inhibitor, scopoletin, were measured in exudates of resistant and susceptible sunflower varieties. It was found that dehydrocostuslactone and orobanchyl acetate are not involved in the resistance of the sunflower varieties studied. The results demonstrate that costunolide, heliolactone, and scopoletin are related to sunflower resistance. The sunflower varieties studied do not use all available options to fight parasitic plants. This could be one of the reasons that sunflower resistance is rapidly overcome by broomrape

Strategies for the synthesis of canonical, non-canonical and analogues of strigolactones, and evaluation of their parasitic weed germination activity

Strigolactones (SLs) are natural products with promising applications as agrochemicals to prevent infestation with parasitic weeds due to their ability to trigger seed germination. However, their use is still limited because of the low yields in which they are isolated from natural sources. As such, numerous studies have led to strategies for obtaining them, and various structural analogues, by organic synthesis. These analogues have focused attention on the study of SLs, as some of them are easier to synthesize and possess enhanced properties, such as the level of bioactivity. This review provides an overview of the synthesis of SLs, subsequently focusing on the production of analogues with the canonical structure. The germinating activity of the compounds is also described herein, with positive effects on different species of the problematic genera Striga, Orobanche and Phelipanche having been found. The highly active analogue GR24 is currently the most widely studied in the literature, and relevant structural-activity relationships have been proposed as a result of the study of derivatives functionalized in different positions. Analogues based on other natural SLs such as strigol and orobanchol have also been developed, as have some novel canonical SLs derived from eudesmanolide or guaianolide sesquiterpene lactones. This review aims to provide useful information for the development of bioactive compounds applicable in new generation herbicides, in an attempt to employ similar compounds to those produced naturally in ecosystems that provoke effective herbicide effects at low concentrations.This work was supported by the ``Ministerio de Economi ' a, Industria y Competitividad'' (MINEICO), Spain, Project AGL2017-88-083-R

Facile Preparation of Bioactive seco-Guaianolides and Guaianolides from Artemisia gorgonum and Evaluation of Their Phytotoxicity

Commercially available santonin was used to synthesize seven sesquiterpene lactones using a facile strategy that involved a high-yielding photochemical reaction. Three natural products from Artemisia gorgonum were synthesized in good yields, and in the case of two compounds, absolute configurations were determined from X-ray quality crystals. The structures previously reported for these compounds were revised. Sesquiterpene lactones were tested using the etiolated wheat coleoptile bioassay, and the most active compounds were assayed in standard target species. seco-Guaianolide (4) showed higher phytotoxic activities than the known herbicide Logran. This high activity could be due to the presence of a cyclopentenedione ring. These results suggest that compound 4 should be involved in defense of A. gorgorum, displaying a wide range of activities that allow proposing them as new leads for development of a natural herbicide model with a seco-guaianolide skeleton

Phytotoxicity Study of Ortho-Disubstituted Disulfides and Their Acyl Derivatives

Six different ortho-disubstituted disulfides were synthesized and evaluated in wheat coleoptiles bioassays. The most active ones were evaluated on seeds of four different plant species (Solanum lycopersicum L., Lolium rigidum Gaudin, Echinochloa crus-galli (L.) Beauvois, and Urochloa decumbens (Stapf) R. D. Webster) to evaluate their effects on the germination and plant growth, presenting, in general, higher activity than the model herbicide Logran. The results shown in this study indicate that these compounds are potential candidates as herbicide leads for weed control in agriculture

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.This research was supported by CAPES-Coordination for the Improvement of Higher Education Personnel (Brazil) (Project 88881.119937/2016-01) and 'Ministerio de Economia, Industria y Competitividad' (MINEICO), Spain, Project AGL2017-88-083-R

Phytotoxicity evaluation of sesquiterpene lactones and diterpenes from species of the Decachaeta, Salvia and Podachaenium genera

Decachaeta, Salvia and Podachaenium genera are known for their wide variety of biological activities. Synthetic herbicides have caused a variety of environmental and resistance problems. Natural products represent an important alternative to combat such issues. Sesquiterpene lactones and diterpenes are families of bioactive natural products for which a range of activities have been described. The bioactivities of nine sesquiterpene lactones, eight heliangolides, one guaianolide and twenty two diterpenes isolated from species of the Decachaeta, Salvia and Podachaenium genera were tested by applying a methodical procedure that involves assays of compounds on etiolated wheat coleoptiles (Triticum aestivum), Standard Target Species (STS) and two important weeds (barnyardgrass and brachiaria). The results clearly show that all of the sesquiterpene lactones studied were active on coleoptiles. In addition, six lactones were phytotoxic on both STS and weeds, meaning that these compounds could be used in the development of natural herbicide models

Allelopathic studies with furanocoumarins isolated from Ducrosia anethifolia. In vitro and in silico investigations to protect legumes, rice and grain crops

Six different furanocoumarins were isolated from the aerial parts of Ducrosia anethifolia and tested in vitro for plant cell elongation in etiolated wheat coleoptile. They were also tested for their ability to control three different weeds: ribwort plantain, annual ryegrass, and common purslane. These compounds exhibited strong inhibition of plant cell elongation. In the case of (+)-heraclenin, the IC50 was lower than 20 μM, indicating a better inhibition than the positive control Logran®. Computational experiments for docking and molecular dynamics revealed for the investigated furanocoumarins bearing an epoxide moiety an improved fitting and stronger interaction with the auxin-like TIR1 ubiquitin ligase. Furthermore, the formed inhibition complex remained also stable during dynamic evaluation. Bidental interaction at the active site, along with an extended hydrogen-bond lifetime, explained the enhanced activity of the epoxides. The in vitro weed bioassay results showed that Plantago lanceolata was the most affected weed for germination, root, and shoot development. In addition, (+)-heraclenin displayed better inhibition values than positive control even at 300 μM concentration