Phytochemical Characterization of Low Molecular Weight Constituents from Marshmallow Roots (<i>Althaea officinalis</i>) and Inhibiting Effects of the Aqueous Extract on Human Hyaluronidase‑1

Extract <i>RE</i> was obtained from the roots of <i>Althaea officinalis</i> 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 <i>RE</i> revealed the presence of <i>N</i>-phenylpropenoyl-l-amino acid amides <b>1</b>–<b>5</b>, 8% glycine betaine <b>6</b>, 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 (<b>12</b>) and four hypolaetin glycosides (<b>7</b>–<b>9</b> and <b>11</b>) with <i>O</i>-sulfocarbohydrate moieties; additionally, 4′-<i>O</i>-methylisoscutellarein-8-<i>O</i>-β-d-(3″-<i>O</i>-sulfo)­glucuronopyranoside (<b>10</b>) and the diglycosylated coumarin haploperoside D (<b>13</b>) were identified. The hypolaetin-<i>O</i>-sulfoglycosides <b>7</b>–<b>10</b> are new natural products. <i>RE</i> inhibited the enzymatic activity of surface-displayed human hyaluronidase-1 on <i>Escherichia coli</i> F470 cells with an IC₅₀ of 7.7 mg/mL. <i>RE</i> downregulated mRNA expression of <i>hyal-1</i> 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