Comprehensive Analysis of Phenolic Compounds in Desf.

Desf. (SG) has been well studied due to the presence of 1,25(OH)D glycosides, but little is known about the composition and presence of other phenolic glycosides that are also part of the plant's composition. In fact, only 8 phenolic ingredients have been described in the literature; thus, the current study aimed to comprehensively extend the phenolic composition. Aqueous leaf extracts were separated by reversed-phase chromatography or, after permethylation, on normal phase chromatography. Two novel quercetin derivatives were isolated, including 7--β-glucosyl-α-apiosyl rutin, which was never reported in the literature before. In total, five quercetin glycosides containing one to four sugar units were determined quantitatively for the first time in SG, reaching a total 4.16% dry matter. Additionally, arbutin and 27 cinnamoyl derivatives were identified and quantitated via LC-MS/MS, totaling 0.57% and 2.15% dry matter of leaves, respectively. The quantitative results were based on independent syntheses of 1--and 3--caffeoyl- and 3--feruloyl glucoside, isolation of 3/4--caffeoyl- and 3/4---coumaroyl glucaric acid from SG leaves, and the use of authentic reference material (3- and 5--cinnamoyl quinic acids). All of the isolated and synthesized substances were unequivocally verified by HR-MS and NMR spectroscopy.