Phytochemistry and Inflorescences Morphometry of Invasive Solidago L. (Goldenrods) Species – Valuable Late Autumn Mellifers

Abstract

In Europe, two invasive North American species of Solidago L. have been detected: S. canadensis L. and S. gigantea Ait. Both species provide a stable late harvest and are valued by beekeepers for their ability to produce pollen and nectar in late fall. There is a significant correlation between the chemical components of flowers and goldenrod honey, so the study of the phytochemical composition of inflorescences (heads) seems to be very actual. The work aims to determine the total content of saccharides, phenolic compounds, and flavonoids in the heads of S. canadensis and S. gigantea for comparative evaluation of bee production quality, and also to specify morphometric differences in the heads of both species and to reveal the amplitude of their variability. The material was collected in the Moscow and Pskov Regions (Russia). The total content of the saccharides in S. canadensis heads was 27.33 ±0.54 %, with monosaccharides ~44–46 %. In S. gigantea’s heads total content of the saccharides was 1.5 times lower – 18.07 ±0.73 %, the content of monosaccharides was 7.39 ±0.15 %. The total content of phenolic compounds in the heads of S. canadensis was 105.36 ±1.45 mg GAE/100 g and in S. gigantea’s heads was 98.41 ±1.71 mg GAE/100 g. The total flavonoid content as quercetin equivalents was 58.23 ±0.17 mg QE/100 g in the heads of S. canadensis and 41.97 ±0.34 mg QE/100 g in S. gigantea’s heads. Thus, in S. canadensis heads the content of the total content of saccharides is 1.5 times higher, the content of phenolic compounds is 1.3 times higher, and the content of flavonoids is 1.4 times higher than in S. gigantea. A feature allowing the diagnosis of these species is the size of the heads: S. canadensis has smaller heads than S. gigantea (4.4×1.8 vs. 6.4×2.3 mm).