Honeybees Tolerate Cyanogenic Glucosides from Clover Nectar and Flowers

Diversity and Chemical Characterization of Apple (Malus sp.) Pollen: High Antioxidant and Nutritional Values for Both Humans and Insects

Pollen represents a reward for pollinators and is a key element in plant-insect interactions, especially in apples, which are entomophilous species and require cross-pollination to produce economically valuable yields. The aim of this study was to analyze the chemical content of the pollen in 11 apple cultivars ('Red Aroma', 'Discovery', 'Summerred', 'Rubinstep', 'Elstar', 'Dolgo', 'Professor Sprenger', 'Asfari', 'Eden', 'Fryd' and 'Katja') grown in Norway and try to establish a relationship between them and insect attractiveness. In the applied chemical analysis, 7 sugars and sugar alcohols, 4 organic acids, 65 phenolic compounds, 18 hydroxycinnamic acid amides (phenylamides), a large number of polypeptides with a molecular weight of 300 kDa to <6.5 kDa, lipids, carotenoids, starch, pectin and cellulose were determined. The crab apples 'Dolgo' and 'Professor Sprenger', which are used as pollenizers in commercial orchards, had the highest level of sucrose, total polyphenol content (prevent oxidative damages in insects), antioxidant capacity, hydroxybenzoic acids and derivatives, quercetin and derivatives, dihyrochalcone, epicatechin, putrescine derivates, and proteins with molecular weight 66-95 kDa and >95 kDa, which made them interesting for insect pollenizers. Only the pollen of the crab apples contained quercetin-3-O-(2″-O-malonyl)-hexoside, which can be used as a marker for the apple species Malus sylvestris (L.) Mill. Apple floral pollen is a rich source of bioactive components and can be used to prevent and/or cure diseases or can be included in diets as a "superfood".

Effects of Apis dorsata Honey on the mRNA Expression of Selected CYP450, Pro-apoptotic, and Anti-apoptotic Genes during Induced Cytotoxicity in Cyclophosphamide-treated Human Lung Carcinoma (A549) Cells

Introduction

One of the novel strategies in cancer treatment is the combination of conventional chemotherapeutic drugs and natural products. In a previous study, co-treatment of the anti-cancer drug cyclophosphamide (CP) with honey from giant honey bee (Apis dorsata) resulted to a dose-dependent increase in its cytotoxic effect in human lung carcinoma (A549) cells. However, the molecular mechanism of this combinatorial effect remains unknown.

Objectives

In this study, the effect of A. dorsata honey on the expression of selected CYP450 genes at the mRNA level, as well as the proapoptotic gene CASP8 and antiapoptotic gene BCL2 was investigated in CP-treated A549 cells.

Methods

MTT Assay was performed to determine the cell viability of A549 cells after treatment with CP with or without A. dorsata honey, as well as the EC50 of CP with honey thereafter. RT-qPCR was then performed to study the effect of A. dorsata honey on the expression of selected CYP450 genes as well as CASP8 and BCL2 genes in CP-treated A549 cells. LC-MS was carried out to screen for putative compounds in A. dorsata honey which may possibly have anti-cancer activity.

Results

Honey in the lowest concentration (0.6% v/v) most effectively enhanced the cytotoxic effect of CP. CYP2J2 and CYP1B1 indicated a 2.38-fold and 1.49-fold upregulation, respectively as compared to untreated cells. This cytotoxic effect is further enhanced by upregulation of CASP8 that is paralleled by a downregulation of BCL2. Phytosphingosine and sphinganine are honey constituents which may be linked to the increased cytotoxicity of CP observed in A549 cells.

Conclusion

This study provides further knowledge on the molecular basis by which A. dorsata honey potentiates the cytotoxic effect of cyclophosphamide in A549 cells.

Phytochemical profiles of honey bees (Apis mellifera) and their larvae differ from the composition of their pollen diet

Pollen and nectar consumed by honey bees contain plant secondary metabolites (PSMs) with vital roles in plant-insect interactions. While PSMs can be toxic to bees, they can also be health-promoting, e.g. by improving pesticide and pathogen tolerances. As xenobiotics, PSMs undergo post-ingestion chemical modifications that can affect their bioactivity and transmission to the brood. Despite the importance of understanding honey bee PSM metabolism and distribution for elucidating bioactivity mechanisms, these aspects remain largely unexplored. In this study, we used HPLC-MS/MS to profile 47 pollen PSMs in honey bees and larvae. Both adult bees and larvae had distinct PSM profiles that differed from their diet. This is likely due to post-ingestion metabolism and compound-dependent variations in PSM transmission to the brood via nurse bee jelly. Phenolic acids and flavonoid aglycones were most abundant in bees and larvae, whereas alkaloids, cyanogenic glycosides and diterpenoids had the lowest abundance despite being consumed in higher concentrations. This study documents larval exposure to a variety of PSMs for the first time, with concentrations increasing from early to late larval instars. Our findings provide novel insights into the post-ingestion fate of PSMs in honey bees, providing a foundation for further exploration of biotransformation pathways and PSM effects on honey bee health.

Host-microbiome metabolism of a plant toxin in bees

While foraging for nectar and pollen, bees are exposed to a myriad of xenobiotics, including plant metabolites, which may exert a wide range of effects on their health. Although the bee genome encodes enzymes that help in the metabolism of xenobiotics, it has lower detoxification gene diversity than the genomes of other insects. Therefore, bees may rely on other components that shape their physiology, such as the microbiota, to degrade potentially toxic molecules. In this study, we show that amygdalin, a cyanogenic glycoside found in honey bee-pollinated almond trees, can be metabolized by both bees and members of the gut microbiota. In microbiota-deprived bees, amygdalin is degraded into prunasin, leading to prunasin accumulation in the midgut and hindgut. In microbiota-colonized bees, on the other hand, amygdalin is degraded even further, and prunasin does not accumulate in the gut, suggesting that the microbiota contribute to the full degradation of amygdalin into hydrogen cyanide. In vitro experiments demonstrated that amygdalin degradation by bee gut bacteria is strain-specific and not characteristic of a particular genus or species. We found strains of Bifidobacterium, Bombilactobacillus, and Gilliamella that can degrade amygdalin. The degradation mechanism appears to vary since only some strains produce prunasin as an intermediate. Finally, we investigated the basis of degradation in Bifidobacterium wkB204, a strain that fully degrades amygdalin. We found overexpression and secretion of several carbohydrate-degrading enzymes, including one in glycoside hydrolase family 3 (GH3). We expressed this GH3 in Escherichia coli and detected prunasin as a byproduct when cell lysates were cultured with amygdalin, supporting its contribution to amygdalin degradation. These findings demonstrate that both host and microbiota can act together to metabolize dietary plant metabolites.

LC-MS/MS Quantification Reveals Ample Gut Uptake and Metabolization of Dietary Phytochemicals in Honey Bees (Apis mellifera)

The honey bee pollen/nectar diet is rich in bioactive phytochemicals and recent studies have demonstrated the potential of phytochemicals to influence honey bee disease resistance. To unravel the role of dietary phytochemicals in honey bee health it is essential to understand phytochemical uptake, bioavailability, and metabolism but presently limited knowledge exists. With this study we aim to build a knowledge foundation. For 5 days, we continuously fed honey bees on eight individual phytochemicals and measured the concentrations in whole and dissected bees by HPLC-MS/MS. Ample phytochemical metabolization was observed, and only 6-30% of the consumed quantities were recovered. Clear differences in metabolization rates were evident, with atropine, aucubin, and triptolide displaying significantly slower metabolism. Phytochemical gut uptake was also demonstrated, and oral bioavailability was 4-31%, with the highest percentages observed for amygdalin, triptolide, and aucubin. We conclude that differences in the chemical properties and structure impact phytochemical uptake and metabolism.

Colony-Level Effects of Amygdalin on Honeybees and Their Microbes

Amygdalin, a cyanogenic glycoside, is found in the nectar and pollen of almond trees, as well as in a variety of other crops, such as cherries, nectarines, apples and others. It is inevitable that western honeybees (Apis mellifera) consistently consume amygdalin during almond pollination season because almond crops are almost exclusively pollinated by honeybees. This study tests the effects of a field-relevant concentration of amygdalin on honeybee microbes and the activities of key honeybee genes. We executed a two-month field trial providing sucrose solutions with or without amygdalin ad libitum to free-flying honeybee colonies. We collected adult worker bees at four time points and used RNA sequencing technology and our HoloBee database to assess global changes in microbes and honeybee transcripts. Our hypothesis was that amygdalin will negatively affect bee microbes and possibly immune gene regulation. Using a log2 fold-change cutoff at two and intraday comparisons, we show no large change of bacterial counts, fungal counts or key bee immune gene transcripts, due to amygdalin treatment in relation to the control. However, relatively large titer decreases in the amygdalin treatment relative to the control were found for several viruses. Chronic bee paralysis virus levels had a sharp decrease (-14.4) with titers then remaining less than the control, Black queen cell virus titers were lower at three time points (<-2) and Deformed wing virus titers were lower at two time points (<-6) in amygdalin-fed compared to sucrose-fed colonies. Titers of Lotmaria passim were lower in the treatment group at three of the four dates (<-4). In contrast, Sacbrood virus had two dates with relative increases in its titers (>2). Overall, viral titers appeared to fluctuate more so than bacteria, as observed by highly inconstant patterns between treatment and control and throughout the season. Our results suggest that amygdalin consumption may reduce several honeybee viruses without affecting other microbes or colony-level expression of immune genes.

Chemical Fingerprint of 'Oblačinska' Sour Cherry (Prunus cerasus L.) Pollen

The aim of this research was to analyze sugars and phenolics of pollen obtained from 15 different ‘Oblačinska’ sour cherry clones and to assess the chemical fingerprint of this cultivar. Carbohydrate analysis was done using high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD), while polyphenols were analyzed by ultra-high-performance liquid chromatography–diode array detector–tandem mass spectrometry (UHPLC-DAD MS/MS) system. Glucose was the most abundant sugar, followed by fructose and sucrose. Some samples had high level of stress sugars, especially trehalose. Rutin was predominantly polyphenol in a quantity up to 181.12 mg/kg (clone III/9), with chlorogenic acid (up to 59.93 mg/kg in clone III/9) and p-coumaric acid (up to 53.99 mg/kg in clone VIII/1) coming after. According to the principal component analysis (PCA), fructose, maltose, maltotriose, sorbitol, and trehalose were the most important sugars in separating pollen samples. PCA showed splitting off clones VIII/1, IV/8, III/9, and V/P according to the quantity of phenolics and dissimilar profiles. Large differences in chemical composition of studied ‘Oblačinska sour cherry’ clone pollen were shown, proving that it is not a cultivar, but population. Finally, due to the highest level of phenolics, clones IV/8, XV/3, and VIII/1 could be singled out as a promising one for producing functional food and/or in medicinal treatments.