Pyrrolizidine Alkaloids: The Botanical Origin of Pollen Collected during the Flowering Period of Echium vulgare and the Stability of Pyrrolizidine Alkaloids in Bee Bread

UHPLC-Q-TOF analysis of pyrrolizidine alkaloids in North-Macedonian honey

Honey contaminated with pyrrolizidine alkaloids (PAs) could pose a risk for human consumption, being a widely consumed food product. A fast and simple LC/MS method for the analysis of pyrrolizidine alkaloids in honey was optimised to collect occurrence data. The extraction efficiency was evaluated by a systematic study of multiple solvent mixtures and clean-up procedures. The best results for PA extraction were obtained using a formic acid/methanol mixture with subsequent clean-up by the QuEChERS method, resulting in a mean recovery range of 91.8-102%. The method validation showed satisfactory intra-day (RSD < 5.1%) and inter-day precision (RSD < 9.1%). The proposed method was applied to 14 samples. A total of six PAs and two N-oxides were detected, with levels between 89 and 8188 µg/kg. This assessment highlights the potential risk of intoxication and the need for further investigations regarding an effective quality system for manufacturers to control PAs in honey.

Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review

Pyrrolizidine alkaloids (PAs) are naturally occurring secondary metabolites of plants. To date, more than 660 types of PAs have been identified from an estimated 6000 plants, and approximately 120 of these PAs are hepatotoxic. As a result of PAs being found in spices, herbal teas, honey, and milk, PAs are considered contaminants in foods, posing a potential risk to human health. Here, we summarize the chemical structure, toxic effects, levels, and regulation of PAs in different countries to provide a better understanding of their toxicity and risk assessment. With recent research on the risk assessment of PAs, this review also discusses the challenges facing this field, aiming to provide a scientific basis for PA toxicity research and safety assessment.

Investigation of Botanical Origin, Phenolic Compounds, Carotenoids, and Antioxidant Properties of Monofloral and Multifloral Bee Bread

Bee bread is a unique natural product made by bees and good for human health. It has many bioactive molecules that can treat or prevent diseases. In this study, melissopalynological methods were used to examine five bee bread samples. Major plant sources found in bee bread were Lotus spp., Trifolium spp., and Xeranthemum spp., which are from the Fabaceae and Asteraceae families. Then, the amount of phenolic compounds and major carotenoids in bee bread (BB) samples were quantified. Gallic acid, caffeic acid, quercetin, and kaempferol were found in all BB samples, with β-carotene being the most abundant carotenoid in all but BB1. In addition, the total phenolic/flavonoid content and antioxidant activities of all BB samples were determined. Total flavonoid, total phenolic, DPPH⋅, and ABTS⋅⁺ values were varied between 5.6-10.00 mg GAE/g DW, 1.2-4.3 mg QE/g DW, 1.2-5.5 mg TEAC/g DW, and 2.6-15.4 mg TEAC/g DW, respectively.

Fate of Food-Relevant Toxic Plant Alkaloids during Food Processing or Storing and Analytical Strategies to Unveil Potential Transformation Products

Toxic plant alkaloids (TPAs) may contaminate food and pose a threat to consumer health; as a consequence, they are undesired in foodstuff or food commodities. Similar to other ingredients, TPA may be affected by storing or processing of food, often associated with decreased levels of the parent alkaloids. Up to now, little is known about potential transformation products or if they still may exhibit toxic potential to consumers. This perspective briefly summarizes the current knowledge regarding the behavior of opium, pyrrolizidine, and tropane alkaloids toward processing or storing and highlights analytical strategies to identify and elucidate potential transformation products.

High abundance of pyrrolizidine alkaloids in bee pollen collected in July 2019 from Southern Germany

Pyrrolizidine alkaloids (PA) are secondary plant defense compounds and known pre-toxins when containing a 1,2-double bond. They are commonly produced by various plants and may thus be present in bee pollen which may be consumed by humans as food supplements. In this study, PA were determined in bee pollen samples from 57 locations in Southern Germany sampled by means of pollen traps in July 2019. Samples were analyzed by using palynological methodology and solid-phase extraction (SPE) followed by LC-MS/MS. In total, 52 pollen samples featured total pyrrolizidine alkaloids (ΣPA) with concentrations up to 48,000 ng/g bee pollen, while the N-oxides (NO) echinatine-NO and rinderine-NO clearly dominated. In contrast, the palynological analysis only detected 33 samples with pollen from PA-producing plants. Accordingly, the results showed that palynological analysis is not sufficient to determine PA in pollen. In addition, a risk assessment was followed to estimate the risk of the detected PA concentrations to humans.

Comparative analysis of the main medicinal substances and applications of Echium vulgare L. and Echium plantagineum L.: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Echium vulgare L. and Echium plantagineum L. originated in the Mediterranean, and were later domesticated in Africa, America, Asia, Europe and Oceania, where they were widely used to treat many diseases including cough, urinary tract infection, fever, inflammation and muscle strain.

AIM OF THE STUDY

The purpose of this review is to provide scientific literature on the traditional uses, bioactive chemical components and pharmacological activities of two species of Echium, and to critically analyze the information provided, so as to understand the current work on these two species and explore the possible prospect of this plant in pharmaceutical research.

METHODS

Systematic review and meta-analysis were conducted according to Prisma guidelines, and the related literatures searched on Google Academic, Science Direct, Baidu Scholars and China National Knowledge Infrastructure (CNKI) up to June 2021 were reviewed. The key words used are: Echium, E.vulgare, E.plantagineum, plant components, chemical components, pharmacological activities, pharmaceutical products and applications. Thereafter all eligible studies are analyzed and summarized in this review. The selection of manuscripts is based on the following inclusion criteria: the article has years of research or publication, is published in English, Portuguese or Spanish and Chinese, and there are keywords in the title, abstract, keywords or full text of the article. For the selection of manuscripts, first, select articles according to titles, then summarize them, and finally, analyze the full text of the publication. Elimination criteria: 1. Duplicate reports; 2. There are research design defects and poor quality; 3. Incomplete data and unclear ending effect; 4. The statistical method is wrong and cannot be corrected.

RESULTS

The pharmacological characteristics of E.vulgare and E.plantagineum can basically support their traditional use, but the medicinal substances contained in them are quite different in composition and content, and the development and application of corresponding products are also different.

CONCLUSIONS

At present, there is little clinical data about drugs related to the two species, and more research is needed in the future, especially human experiments and clinical trials, to evaluate the cellular and molecular mechanisms based on pharmacological, biological activity and safety studies, and to provide more powerful scientific basis for their traditional medicinal properties. In addition, the further application and development of the medicinal products of E.vulgare and E.plantagineum still need to be precise and identified, so as to give full play to their medicinal potential.

Characterization and Lifetime Dietary Risk Assessment of Eighteen Pyrrolizidine Alkaloids and Pyrrolizidine Alkaloid N-Oxides in New Zealand Honey

Pyrrolizidine alkaloids (PAs) are a large group of botanical toxins of concern, as they are considered genotoxic carcinogens, with long-term dietary exposure presenting an elevated risk of liver cancer. PAs can contaminate honey through honeybees visiting the flowers of PA-containing plant species. A program of monitoring New Zealand honey has been undertaken over several years to build a comprehensive dataset on the concentration, regional and seasonal distribution, and botanical origin of 18 PAs and PA N-oxides. A bespoke probabilistic exposure model has then been used to assess the averaged lifetime dietary risk to honey consumers, with exposures at each percentile of the model characterized for risk using a margin of exposure from the Joint World Health Organization and United Nations Food and Agriculture Organization Expert Committee on Food Additives (JECFA) Benchmark Dose. Survey findings identify the typical PA types for New Zealand honey as lycopsamine, echimidine, retrorsine and senecionine. Regional and seasonal variation is evident in the types and levels of total PAs, linked to the ranges and flowering times of certain plants. Over a lifetime basis, the average exposure an individual will receive through honey consumption is considered within tolerable levels, although there are uncertainties over high and brand-loyal consumers, and other dietary contributors. An average lifetime risk to the general population from PAs in honey is not expected. However, given the uncertainties in the assessment, risk management approaches to limit or reduce exposures through honey are still of value.

Metabolic Toxification of 1,2-Unsaturated Pyrrolizidine Alkaloids Causes Human Hepatic Sinusoidal Obstruction Syndrome: The Update

Saturated and unsaturated pyrrolizidine alkaloids (PAs) are present in more than 6000 plant species growing in countries all over the world. They have a typical heterocyclic structure in common, but differ in their potential toxicity, depending on the presence or absence of a double bond between C1 and C2. Fortunately, most plants contain saturated PAs without this double bond and are therefore not toxic for consumption by humans or animals. In a minority of plants, however, PAs with this double bond between C1 and C2 exhibit strong hepatotoxic, genotoxic, cytotoxic, neurotoxic, and tumorigenic potentials. If consumed in error and in large emouns, plants with 1,2-unsaturated PAs induce metabolic breaking-off of the double bonds of the unsaturated PAs, generating PA radicals that may trigger severe liver injury through a process involving microsomal P450 (CYP), with preference of its isoforms CYP 2A6, CYP 3A4, and CYP 3A5. This toxifying CYP-dependent conversion occurs primarily in the endoplasmic reticulum of the hepatocytes equivalent to the microsomal fraction. Toxified PAs injure the protein membranes of hepatocytes, and after passing their plasma membranes, more so the liver sinusoidal endothelial cells (LSECs), leading to life-threatening hepatic sinusoidal obstruction syndrome (HSOS). This injury is easily diagnosed by blood pyrrolizidine protein adducts, which are perfect diagnostic biomarkers, supporting causality evaluation using the updated RUCAM (Roussel Uclaf Causality Assessment Method). HSOS is clinically characterized by weight gain due to fluid accumulation (ascites, pleural effusion, and edema), and may lead to acute liver failure, liver transplantation, or death. In conclusion, plant-derived PAs with a double bond between C1 and C2 are potentially hepatotoxic after metabolic removal of the double bond, and may cause PA-HSOS with a potential lethal outcome, even if PA consumption is stopped.

Natural contaminants in bee pollen: DNA metabarcoding as a tool to identify floral sources of pyrrolizidine alkaloids and fungal diversity

The use of bee pollen as a food supplement has increased in recent years as it contains several nutrients and phytochemicals. However, depending on floral composition, bee pollen can be contaminated by pyrrolizidine alkaloids (PAs), PA N-oxides (PANOs) and toxigenic fungi found in plants, which may pose a potential health risk for consumers. Thus, a DNA metabarcoding approach based on internal transcribed spacer 2 (ITS2) region was used to identify the plant sources of 17 PAs/PANOs detected by a validated method in liquid chromatography coupled to mass spectrometry (LC-MS/MS), as well as floral and fungal diversity in 61 bee pollen samples. According to LC-MS/MS analysis, 67% of the samples contained PAs/PANOs with mean concentration of 339 µg/kg. The contamination pattern was characterised by lycopsamine- and senecionine-type PAs/PANOs. PA/PANO-producing plants were identified in 54% of the PA/PANO-contaminated samples analysed by DNA metabarcoding, which also allowed identifying the overall floral and fungal composition of 56 samples. To evaluate the performance of the molecular approach, a subset of 25 samples was analysed by classical palynology. Palynological analysis partially confirmed the results of DNA metabarcoding, which had a better performance in distinguishing pollens of different genera from Asteraceae (76%) and Brassicaceae (88%). However, the molecular analysis did not identify pollens from Castanea, Eucalyptus, Hedera and Salix, which were abundant in 11 samples according to palynology. On the other hand, the molecular analysis allowed identifying several fungal genera in 33 samples, including the toxigenic fungi Alternaria and Aspergillus, which were positively correlated to the plant genus Hypericum. Despite limitations in identifying some pollen types, these preliminary results suggest that the DNA metabarcoding could be applied in a multidisciplinary approach to give a picture of floral and fungal diversity, which can be sources of natural contaminants in bee pollen and would help to control its safety.

Pyrrolizidine alkaloids and beehive products: A review

Pyrrolizidine alkaloids (PA) are secondary metabolites of plants, which are mostly found in the genus Senecio, Echium, Crotalaria, and Eupatorium. The presence of 1,2-unsaturated PA in foods is a concern to food regulators around the world because these compounds have been associated to acute and chronic toxicity, mainly in the liver. The intake foods with PA/PANO usually occur through accidental ingestion of plants and their derivatives, besides to products of vegetal-animal origin, such as honey. PA/PANO are transferred to honey by their presence in nectar, honeydew, and pollen, which are collected from the flora by bees. In addition to honey, other beekeeping products, such as pollen, royal jelly, propolis, and beeswax, are also vulnerable to PA contamination. In this context, this review provides information about chemical characteristics, regulation, and toxicity, as well as summarizes and critically discusses scientific publications that evaluated PA in honeys, pollens, royal jelly, and propolis.

Discriminant analysis of pyrrolizidine alkaloid contamination in bee pollen based on near-infrared data from lab-stationary and portable spectrometers

Bee pollen may be contaminated with pyrrolizidine alkaloids (PAs) and their N-oxides (PANOs), which are mainly detected by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS), even though the use of fast near-infrared (NIR) spectroscopy is an ongoing alternative. Therefore, the main challenge of this study was to assess the feasibility of both a lab-stationary (Foss) and a portable (Polispec) NIR spectrometer in 60 dehydrated bee pollen samples. After an ANOVA-feature selection of the most informative NIR spectral data, canonical discriminant analysis (CDA) was performed to distinguish three quantitative PA/PANO classes (µg/kg): < LOQ (0.4), low; 0.4–400, moderate; > 400, high. According to the LC–MS/MS analysis, 77% of the samples were contaminated with PAs/PANOs and the sum content of the 17 target analytes was higher than 400 µg/kg in 28% of the samples. CDA was carried out on a pool of 18 (Foss) and 22 (Polispec) selected spectral variables and allowed accurate classification of samples from the low class as confirmed by the high values of Matthews correlation coefficient (≥ 0.91) for both NIR spectrometers. Leave-one-out cross-validation highlighted precise recognition of samples characterised by a high PA/PANO content with a low misclassification rate (0.02) as false negatives. The most informative wavelengths were within the < 1000, 1000–1660 and > 2400 nm regions for Foss and > 1500 nm for Polispec that could be associated with cyclic amines, and epoxide chemical structures of PAs/PANOs. In sum, both lab-stationary and portable NIR systems are reliable and fast techniques for detecting PA/PANO contamination in bee pollen.

Spread of Jacobaea vulgaris and Occurrence of Pyrrolizidine Alkaloids in Regionally Produced Honeys from Northern Germany: Inter- and Intra-Site Variations and Risk Assessment for Special Consumer Groups

Pyrrolizidine alkaloids (PA) and PA N-oxides (PANO) are secondary plant metabolites exhibiting genotoxic and carcinogenic properties. Apart from the roots and leaves, PA/PANO are particularly present in pollen and nectar. Therefore, the spread of Jacobaea vulgaris in certain regions of northern Germany has an impact on the safety of honey produced in that region. In this study, raw honey samples (n = 437) were collected from usually three individual beehives per site (n = 73) in the district of Ostholstein and analyzed for 25 PA/PANO. The results reveal mean levels of 8.4, 1.5, and 72.6 µg/kg and maximum levels of 111, 59.4, and 3313 µg/kg, depending on the season (summer 2015 and spring/summer 2016, respectively). As far as individual data are concerned, sites near areas with J. vulgaris growth did not necessarily result in high PA/PANO values. Furthermore, intra-site investigations revealed remarkable differences in PA/PANO levels of raw honey collected by different bee colonies at the same site. Consumption of these regionally produced honeys entails an increased exposure to PA/PANO, especially in children and high consumers. Margin of exposure values of <10,000 and an exceedance of the health-based guidance value highlight that regionally produced and marketed honey must be considered with care for a proper risk assessment and risk management.

Safflospermidines from the bee pollen of Helianthus annuus L. exhibit a higher in vitro antityrosinase activity than kojic acid

Background

Ozone deterioration in the atmosphere has become a severe problem causing overexposure of ultraviolet light, which results in humans in melanin overproduction and can lead to many diseases, such as skin cancer and melasma, as well as undesirable esthetic appearances, such as freckles and hyperpigmentation. Although many compounds inhibit melanin overproduction, some of them are cytotoxic, unstable, and can cause skin irritation. Thus, searching for new natural compounds with antityrosinase activity and less/no side effects is still required. Here, bee pollen derived from sunflower (Helianthus annuus L.) was evaluated.

Materials and methods

Sunflower bee pollen (SBP) was collected from Apis mellifera bees in Lopburi province, Thailand in 2017, extracted by methanol and sequentially partitioned with hexane and dichloromethane (DCM). The in vitro antityrosinase activity was evaluated using mushroom tyrosinase and the half maximal inhibitory concentration (IC₅₀) is reported. The antioxidation activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and reported as the half maximal effective concentration. Two pure compounds with antityrosinase activity were isolated by silica gel 60 column chromatography (SG₆₀CC) and high performance liquid chromatography (HPLC), and their chemical structure deduced by Nuclear Magnetic Resonance (NMR) analysis.

Results

The DCM partitioned extract of SBP (DCMSBP) had an antityrosinase activity (IC₅₀, 159.4 μg/mL) and was fractionated by SG₆₀CC, providing five fractions (DCMSBP1-5). The DCMSBP5 fraction was the most active (IC₅₀ = 18.8 μg/mL) and further fractionation by HPLC gave two active fractions, revealed by NMR analysis to be safflospermidine A and B. Interestingly, both safflospermidine A and B had a higher antityrosinase activity (IC₅₀ of 13.8 and 31.8 μM, respectively) than kojic acid (IC₅₀ of 44.0 μM). However, fraction DCMSBP5 had no significant antioxidation activity, while fractions DCMSBP1-4 showed a lower antioxidation activity than ascorbic acid.

Conclusion

Safflospermidine A and B are potential natural tyrosinase inhibitors.

Pyrrolizidine alkaloids in bee pollen identified by LC-MS/MS analysis and colour parameters using multivariate class modeling

Toxic pyrrolizidine alkaloids (PAs) and their N-oxides (PANOs) can be present in bee pollen depending on the plants visited by bees. A liquid chromatography-mass spectrometry (LC-MS/MS) method was developed and validated to monitor 17 PAs/PANOs in 44 bee pollens. The CIE-L∗a∗b∗ colour coordinates with the specular component either included or excluded were recorded in pellets and ground aliquots. Lightness (L∗) and yellowness (b∗) of ground bee pollen were significantly correlated to PAs/PANOs content. The L∗ and b∗ cut-offs sorted by a receiver operating characteristic analysis to predict PAs/PANOs presence showed a significant increase in the relative risk to detect amounts higher than 84 μg kg-1. Two supervised canonical discriminant analyses confirmed that pollen without PAs could be distinguished from those containing PAs/PANOs. The data suggest that instrumental colour coupled with supervised models could be used as a screening test for PAs/PANOs in bee pollen, before the confirmatory LC-MS/MS analysis.

The Application of Pollen as a Functional Food and Feed Ingredient-The Present and Perspectives

Pollen is recognized as an excellent dietary supplement for human nutrition, which is why it can be found in different forms on the market (granules, capsules, tablets, pellets, and powders). But, the digestibility of pollen’s nutrients is strongly affected by the presence of a pollen shell, which can decrease the bioavailability of nutrients by 50% and more. Since consumers have become more aware of the benefits of a healthy diet and the necessity to improve pollen digestibility, different pollen-based functional food products have been developed and extensive studies were done to estimate the beneficial effects of pollen-based feed on animal growth, health, and rigor mortise stage. Considering the positive effects of pollen nutrients and phytometabolites on human and animal health, the aim of this paper was to give an overview of recent achievements in the application of pollen in the formulation of functional food and animal diets. Special attention was paid to the effects of pollen’s addition on the nutritional, functional, techno-functional, and sensory properties of the new formulated food products. Anti-nutritional properties of pollen were also discussed. This review points out the benefits of pollen addition to food and feed and the possible directions in the further development of functional food and feed for the wellbeing of everyone.