Identification of the Toxic Compounds in Camellia oleifera Honey and Pollen to Honey Bees (Apis mellifera)

Abstract

Identifying the components of Camellia oleifera honey and pollen and conducting corresponding toxicological tests are essential to revealing the mechanism of Camellia oleifera toxicity to honey bees. In this research, we investigated the saccharides and alkaloids in honey, nectar, and pollen from Camellia oleifera, which were compared with honey, nectar, and pollen from Brassica napus, a widely planted flowering plant. The result showed that melibiose, manninotriose, raffinose, stachyose, and lower amounts of santonin and caffeine were found in Camellia oleifera nectar, pollen, and honey but not in B. napus nectar, pollen, and honey. Toxicological experiments indicated that manninotriose, raffinose, and stachyose in Camellia oleifera honey are toxic to bees, while alkaloids in Camellia oleifera pollen are not toxic to honey bees. The toxicity mechanism of oligosaccharides revealed by temporal metabolic profiling is that oligosaccharides cannot be further digested by honey bees and thus get accumulated in honey bees, disturbing the synthesis and metabolism of trehalose, ultimately causing honey bee mortality.

Caffeine Consumption Helps Honey Bees Fight a Bacterial Pathogen

“…As important as the finding of protection against pathogens is the finding that exposure to low doses of caffeine has no evident fitness cost to bees. Survival rates of caffeine-exposed bees usually increase ( 22 ) or remain the same ( 30 ), at least under concentrations found in nectar. In our study, caffeine exposure did not affect survival rates of honey bees, although we observed a trend toward increased survival rates.…”

“…However, this increased persistence and specificity to a forage location may lead to suboptimal foraging strategies on caffeinated nectar sources with low sugar content ( 24 , 26 ). Moreover, naturally occurring concentrations of caffeine may help to ameliorate effects caused by insecticide exposure in bees ( 27 – 29 ), and they do not impact survival rates of larvae or worker bees ( 30 ), sometimes even improving survival rates ( 22 ).…”

Kaempferitrin: A Flavonoid Marker to Distinguish Camellia oleifera Honey

“…plants. Previous studies have found that C. oleifera honey contains oligosaccharides (manninotriose, raffinose, and stachyose), and it can lead to the death of honeybee larvae and adult worker bees [ 12 , 13 ]. Raffinose and stachyose are classified as raffinose family oligosaccharides (RFOs), one type of prebiotic that has biological functions such as regulating gut flora, preventing inflammatory bowel disease, protecting the liver, and lowering blood sugar and blood lipids, etc., [ 14 , 15 , 16 , 17 ].…”

Distant Hybridization: A Potential Solution to the Pollination Deficit of Camellia oleifera

“…In an effort to address the lack of pollinators for C. oleifera , raised honey bees have been introduced. Because the raffinose, stachyose, and manninotriose in the nectar of C. oleifera are toxic to both larval and adult honey bees, however, C. oleifera flowers are only weakly attractive to the honey bees . Moreover, the toxic nectar of C. oleifera flowers can cause the demise of bee colonies when honey bees are raised in C. oleifera woodlands, thereby resulting in economic losses for bee keepers.…”

“…Pollination deficit is a key issue that is impeding the production of C. oleifera , and one strategy for resolving this issue lies in addressing the conflict between C. oleifera and honey bees. However, to date, the studies conducted on the 16 varieties of C. oleifera that are mainstream modern varieties in C. oleifera oil production in China are focused on fruit yield and quality, except one report in which the chemical composition of nectar and pollen from the mixed sample ‘Xianglin 210’ and ‘Changlin 4’ has been identified . In this report, the toxic sugar content of stachyose in the nectar is higher than that of manninotriose, which is similar to our result.…”