Phenolic Compounds in Nectar of Crataegus monogyna Jacq. and Prunus spinosa L.

Abstract

Crataegus monogyna Jacq. and Prunus spinosa L. are common spring-flowering species in Slovenia. They occur in large stands and sometimes overgrow in unmanaged meadows. They are known as an excellent source of nectar for bees and other pollinators. Phenolic compounds are known as antioxidant for both pollinators and plants. We were interested in comparing plant species in terms of their phenolic compound content: rutin, quercetin, (iso)quercitrin, chlorogenic acid, and hyperoside. Their nectar was obtained from both plant species in 2024 in Ljubljana and the area surrounding Ljubljana. We took 96 samples of each species. The nectar was sampled with microcapillary tubes and analysed by HPLC. When studying the influence of abiotic factors on the concentration of phenolic compounds, the correlations were weak, so we cannot say with certainty which environmental factors affect which phenolic compounds and in what way. Rutin is predominant in the nectar of P. spinosa and chlorogenic acid is predominant in the nectar of C. monogyna. Hyperoside is found in the lowest concentration in both plant species. We found that although C. monogyna secreted much less nectar at midday, it was more concentrated in phenolic compounds at this time than in the morning. In P. spinosa, nectar secretion was highest in the morning, and the concentration of phenolic compounds was also highest in the morning.