Extract RE was obtained from the roots of Althaea officinalis in a yield of 8.1%, related to the dried plant material, by extraction with MeOH-H2O (1:1), followed by precipitation with EtOH to remove high molecular weight constituents. Phytochemical investigation of RE revealed the presence of N-phenylpropenoyl-l-amino acid amides 1-5, 8% glycine betaine 6, about 9% total amino acids with proline as the main compound, and about 61% mono- and oligomeric carbohydrates with sucrose as the main compound. Further fractionation revealed the presence of a hypolaetin diglycoside (12) and four hypolaetin glycosides (7-9 and 11) with O-sulfocarbohydrate moieties; additionally, 4'-O-methylisoscutellarein-8-O-β-d-(3″-O-sulfo)glucuronopyranoside (10) and the diglycosylated coumarin haploperoside D (13) were identified. The hypolaetin-O-sulfoglycosides 7-10 are new natural products. RE inhibited the enzymatic activity of surface-displayed human hyaluronidase-1 on Escherichia coli F470 cells with an IC50 of 7.7 mg/mL. RE downregulated mRNA expression of hyal-1 in HaCaT keratinocytes at 125 and 250 μg/mL, respectively. These data contribute to a deeper phytochemical understanding of marshmallow root extracts and to the positive influence of extracts used for therapy of irritated and inflamed buccal tissue and cough.