Occurrence of Benzoic Acid Esters as Putative Catabolites of Prunasin in Senescent Leaves of <i>Prunus laurocerasus</i>

<i>Prunus laurocerasus</i> is an evergreen shrub containing large quantities of the cyanogenic glycoside prunasin (<b>1</b>) in its leaves, which decomposes to prunasin amide (<b>2</b>) or glucose-1-benzoate (<b>4</b>) when the leaves become chlorotic as a result of senescence or pseudosenescence. This study was aimed at the systematic identification of senescence-associated metabolites to contribute further insight into the catabolism of <b>1</b>. LC-ESIMS profiles of senescent and green leaves were analyzed by principal component analysis. In senescent leaves, the concentrations of 36 compounds were increased significantly including several benzoic acid derivatives, of which prunasin amide-6′-benzoate (<b>5</b>) and prunasin acid-6′-benzoate (<b>6</b>) were isolated and identified. The observed metabolic changes were also induced by treatment of <i>P. laurocerasus</i> shrubs with exogenous ethylene. The data presented support an oxidative catabolism of <b>1</b> without release of hydrogen cyanide and the remobilization of its nitrogen in the course of senescence. The results are discussed in the context of functional diversification and drug discovery, where senescent plant material represents a widely unexplored source for the discovery of natural products

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