Phenolic Compounds from Hypericum cerastoides (Spach) N. Robson: Dereplication via UHPLC-HRMS/MS, Isolation, Identification, and Preliminary Biological Evaluation Focusing on Radical-Scavenging, Anti-α-Glucosidase, and Pro-Lipase Activities

<b>Background/Objectives:</b><i>Hypericum cerastoides</i> (Spach) N. Robson is a lesser-known species with potential pharmacological importance. This study aimed to profile phenolic compounds in its aerial parts and assess biological activities of isolated constituents, focusing on radical-scavenging, anti-α-glucosidase, and pro-lipase effects. <b>Methods:</b> Phenolic compounds from <i>H. cerastoides</i> aerial parts were dereplicated via UHPLC-HRMS/MS. The structures of isolated compounds were determined using spectroscopic methods (1D and 2D NMR, UV, and HRMS-ESI). Radical-scavenging was evaluated by DPPH and ABTS assays; anti-α-glucosidase and pro-lipase activities were measured by LC-MS. <b>Results:</b> UHPLC-HRMS profiling of a hydroalcoholic extract tentatively identified and quantified 39 phenolic compounds, mainly flavonoids and hydroxycinnamic acid derivatives. Furthermore, two new phenolic compounds, namely hypercerastoside A (<b>HC4</b>) and hypercerastoside B (<b>HC6</b>), together with three known compounds, coumaroylquinic acid (<b>HC1</b>), myricetin-3-O-glycoside (<b>HC2</b>), and myricetin-3-O-galactoside (<b>HC3</b>), as well as two artifacts, namely methyl ester of chlorogenic acid (<b>HC5</b>) and hypercerastoside C (<b>HC7</b>), were isolated from the ethylacetate extract of the aerial parts of title plant. Compounds <b>HC2</b>, <b>HC3</b>, and <b>HC5</b> displayed the highest radical-scavenging activity. The anti-α-glucosidase test showed that compounds <b>HC1</b> (IC₅₀ = 44 µM) and <b>HC3</b> (IC₅₀ = 206 µM) possessed similar activity to acarbose (IC₅₀ = 206 µM). Myricetin glycosides <b>HC2</b> and <b>HC3</b> enhanced lipase activity fivefold at 200 µM. <b>Conclusions:</b><i>H. cerastoides</i> is a promising source of bioactive phenolic compounds with significant radical-scavenging and enzyme-modulating activities. These preliminary findings support further exploration of its therapeutic potential, especially for oxidative stress-related disorders, type 2 diabetes, and cachexia.