Separation and quantitative analysis of natural pyrethrins by high-performance liquid chromatography

Tanacetum species: Bridging empirical knowledge, phytochemistry, nutritional value, health benefits and clinical evidence

Introduction: The Tanacetum genus consists of 160 accepted flowering species thriving throughout temperate regions, mainly in the Mediterranean Basin, Northern America, and southwestern and eastern Asia. Tanacetum species bear a long-standing record of use in the folk medicine of indigenous tribes and communities worldwide, along with multitudinous applications in traditional cuisines, cosmeceuticals, and agricultural fields. Methods: Up-to-date data related to traditional uses, phytochemistry, biological activities, toxicity and clinical trials of the genus Tanacetum were systematically reviewed from several online scientific engines, including PubMed, Web of Science, Scopus, SciFinder, Wiley Online, Science Direct, and Cochrane library. Results and discussion: Over the past three decades, 241 metabolites have been isolated from nearly twenty species, including phenolic acids, flavonoids, coumarins, fatty acids and alkanes, aldehydes, volatile compounds, and naphthoquinones. Some unique metabolites have also been identified, such as the ceramides tanacetamide (A-D) from T. artemisioides, pyrethrins from T. cinerariifolium, and sesquiterpene lactones from several species. However, these secondary metabolites are still poorly studied despite in vitro clues highlighting their colossal pharmacological properties, especially as hypotensive, neuroprotective, anticancer, and antimicrobial agents. Scientific studies have validated some traditional claims of the plant, such as antidiabetic, anticancer, anthelmintic, insecticide, antioxidant, and hepatoprotective activities, as well as against festering wounds, skin ulcers, urinary tract infections, and sexually transmitted diseases. Other ethnomedicinal uses for arthritis, gout, rheumatism, anemia, and as a litholytic, antivenom and diaphoretic have not yet been supported and would constitute the subject of further research.

Pyrethrum extract induces oxidative DNA damage and AMPK/mTOR-mediated autophagy in SH-SY5Y cells

Pyrethrum extract is used to produce the most widely applied botanical pesticides in agriculture. Though it primarily targets voltage-gated sodium channels in pests, its toxic effects in non-target systems, particularly in humans, is unclear. In this study, we investigated potential cytotoxic effects and their underlying mechanisms on human nerve cells in vitro. We found that pyrethrum extract exposure markedly inhibited cell viability and triggered oxidative DNA damage in human SH-SY5Y cells. It also induced LC3-II formation, upregulated Beclin-1 protein production, downregulated p62 protein production, and facilitated the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR). These results indicate that cytotoxic exposure to pyrethrum extract could be associated with AMPK/mTOR-mediated autophagy in human nerve cells. Furthermore, the oxidative DNA damage suggests that pyrethrum extract exerts severe toxic effects on human nerve cells. In conclusion, pyrethrum extract carries a risk to human health by inducing cytotoxicity.

Augmentation of pyrethrins content in callus of Chrysanthemum cinerariaefolium and establishing its insecticidal activity by molecular docking of NavMS Sodium Channel Pore receptor

Pyrethrins are effective food-grade bio-pesticides obtained from the flowers of Chrysanthemum cinerariaefolium and this crop cannot be cultivated widely in India due to its specific agro-climatic requirement. Hence pyrethrins are mostly imported from Kenya. Therefore, the present study aims to develop a process for augmentation of pyrethrin contents in C. cinerariaefolium callus and establish the correlation between early knockdown effects through docking on grain storage insect. In vitro seedlings were used as explants to induce callus on MS medium with different concentrations of auxins and cytokinins. Pyrethrin extracted from the callus was estimated by RP-HPLC. In callus, total pyrethrin was found to be 17.5 µg/g, which is higher than that found in natural flowers of certain Pyrethrum cultivars. The concentrations of cinerin II, pyrethrin II and jasmoline II were quite high in callus grown on solid medium. Bio-efficacy of pyrethrum extracts of flower and callus on insect Tribolium sp., showed higher repellency and early knock-down effect when compared with pure compound pestanal. Further, the rapid knockdown effect of all pyrethrins components was established by molecular docking studies targeting NavMS Sodium Channel Pore receptor docking followed by multiple ligands simultaneous docking, performed to investigate the concurrent binding of different combinations of pyrethrin. Among the six pyrethrin components, the pyrethrin I and II were found to be a more efficient, binding more firmly to the target, exhibiting higher possibilities of insecticidal effect by an early knockdown mechanism.

Determination of natural pyrethrins by liquid chromatography-electron ionisation-mass spectrometry

INTRODUCTION

Pyrethrum extract is a mixture of six insecticidal compounds from the flower heads of Chrysanthemum cinerariaefolium L.. Since they only have low to moderate mammalian toxicity they can be used as natural insecticides in agriculture or to develop low cost and safe dermatological formulations. Because of the thermal instability of pyrethrins, analytical methods based on liquid chromatography (LC) are preferred over those based on gas chromatography (GC). A few applications using LC with mass spectrometry detection are presented in the literature. Current protocols for their characterisation by LC rely on the use of less sophisticated detectors such as UV detection.

OBJECTIVE

To develop the first liquid chromatography-electron ionisation-mass spectrometry (LC-EI-MS) method for pyrethrins detection and quantitation in pyrethrum extracts.

METHODOLOGY

A commercial pyrethrum extract and various samples of flower heads from C. cinerariaefolium L. were investigated using reversed-phase nano-liquid chromatography coupled to direct electron ionisation-mass spectrometry (nanoLC-direct EI-MS). The eluted compounds were identified through searches of the US National Institute of Standards and Technology (NIST) library, exploiting the direct EI capability to produce high quality EI mass spectra.

RESULTS

The method demonstrated satisfactory sensitivity (limit of detection (LOD) range: 0.04-0.38 mg/g), linearity (R² range: 0.9740-0.9983) and precision (RSD% range: 4-13%) for the quantitation of the natural pyrethrins in extracts from C. cinerariaefolium L.

CONCLUSION

The nanoLC-direct EI-MS technique can be a useful tool for the detection of pyrethrins.

Antiplasmodial and antitrypanosomal activity of pyrethrins and pyrethroids

In a screen of 1800 plant and fungal extracts for antiplasmodial, antitrypanosomal, and leishmanicidal activity, the n-hexane extract of Chrysanthemum cinerariifolium (Trevir.) Vis. flowers showed strong activity against Plasmodium falciparum. We isolated the five pyrethrins [i.e., pyrethrin II (1), jasmolin II (2), cinerin II (3), pyrethrin I (4), and jasmolin I (5)] from this extract. These were tested together with 15 synthetic pyrethroids for their activity against P. falciparum and Trypanosoma brucei rhodesiense and for cytotoxicity in rat myoblast L6 cells. The natural pyrethrins showed antiplasmodial activity with IC(50)s between 4 and 12 μM, and antitrypanosomal activity with IC(50)s from 7 to 31 μM. The pyrethroids exhibited weaker antiplasmodial and antitrypanosomal activity than the pyrethrins. Both pyrethrins and pyrethroids showed moderate cytotoxicity against L6 cells. Pyrethrin II (1) was the most selective antiplasmodial compound, with a selectivity index of 24.

Advanced method using microwaves and solid-phase microextraction coupled with gas chromatography–mass spectrometry for the determination of pyrethroid residues in strawberries

A microwave-assisted desorption method was developed and coupled with solid-phase microextraction and GC-MS for the analysis of pyrethroid residues in strawberries. In the first step, pyrethroid analytes were desorbed from the whole fruits in an aqueous acetonitrile solution at 50% under microwave assistance, so preventing these compounds to be captured with strong matrix effects by endogenous constituents. Then, the 100 microm poly(dimethylsiloxane)-coated fibre was exposed for 30 min in the obtained extracting solution. Calibration curves, realised from blank strawberries spiked at different concentrations with standards, showed a linear range between 1 microg/kg and 250 microg/kg with r2 > 0.992 and variation coefficients below 15%. Limits of detection and quantitation were found lower than 14 microg/kg and 40 microg/kg, respectively. Observed analysis results by using this method and relative to field incurred strawberry samples were also compared to those obtained by two accredited trading laboratories using traditional methods.

Action of pyrethrum-based formulations against grain weevils

Pyrethrum extract, containing six insecticidal esters, has a long history of successful application in the control of stored products. Its low environmental hazard makes it an ideal pesticide for outdoor pre-harvest treatment. However the disadvantage of its low light stability then becomes apparent. This drawback can be overcome by the complexation of pyrethrum extract with gamma-cyclodextrin. Primary object of the conducted studies was to investigate the effect of complexation upon the insecticidal action against the grain weevil, an important storage pest in temperate climates. To slow down the quick metabolism of pyrethrum by the insects' microsomal system synergistic substances are added. Additional to the already well-known piperonyl butoxide two natural synergists, sesamol and tocopherol acetate, were combined with pyrethrum extract to investigate their synergistic activity. A complex of pyrethrum with gamma-cyclodextrin, with piperonyl butoxide as synergist, has a slightly enhanced action compared to a commercial product, which contained pyrethrum in its free form. Sesamol and tocopherol acetate also display a synergistic action, but to a much smaller degree, even if applied in larger amounts. The optimal concentration of pyrethrum was found to be 0.3% combined with 3% piperonyl butoxide.

Selective enrichment of 17 pyrethroids from lyophilised agricultural samples

The screening of agricultural samples to determine 17 synthetic pyrethroids was investigated. Samples were lyophilised without losses of the insecticides, and then extracted with n-hexane. A simple, continuous preconcentration-elution system was developed, which included a silica sorbent column (packed with 50 mg) and used an air stream to carry the eluent (ethyl acetate) which minimised the eluate volume thus increasing the preconcentration factor; so no evaporation step was required. Pyrethroids were determined by gas chromatography-electron capture detection (GC-ECD) by using a 5% phenylmethylpolysiloxane-coated fused-silica capillary column; gas chromatography-mass spectrometry was used to identify the pyrethroids detected by GC-ECD monitoring. Limits of detection varied between 0.1 and 0.8 ng/ml (except for piperonyl butoxide, 25 ng/ml) with linear ranges from 1 to 200 ng/ml; the precision of the method was high (3-6%). Recoveries of 17 insecticides from 14 different agricultural samples fortified at levels of 20-100 ng/g ranged from 66 to 102% (bifenthrin and deltamethrin were those providing the lowest values, 66-87%). Pyrethroids were detected in eight samples (from the 100 unfortified agricultural samples tested) at concentrations lower than the established maximum residue limits (MRLs).

Separation of the insecticidal pyrethrin esters by capillary electrochromatography

A simple, rapid technique for the direct separation and quantification of the six insecticidally active pyrethrin esters in typical extracts and commercial formulations by capillary electrochromatography (CEC) has been described. The separation of the pyrethrin esters was achieved by optimizing several parameters including the length of stationary phase, the mobile phase composition and column temperature. The mobile phase composition had the most pronounced effect toward resolving these structurally similar compounds. A ternary mobile phase composed of acetonitrile-aqueous buffer-tetrahydrofuran (55:35:10) provided the elutropic solvent strength needed to resolve the six esters from an extract mixture in under 16 min. A 25 cm packed bed of Hypersil 3 microm C18 stationary phase was used with the ternary mobile phase at 25 degrees C and 30 kV voltage. These conditions also yielded excellent separation of the pyrethrin esters in two different commercially available insecticidal formulations. In addition, the developed CEC method was shown to be a fast and easy way of quantifying the amount of these esters in typical pyrethrin formulations.