Three New Prenylated Dihydrobenzofurans and a New Flavonoid Glycoside from the Aerial Parts of Myrsine seguinii

In this study, we aimed to determine the chemical constituents of <i>M. seguinii</i>, which led to the isolation and identification of 26 compounds. Three new prenylated dihydrobenzofurans [myrsinoic acids I (<b>1</b>), J (<b>2</b>), and K (<b>3</b>)] and a new flavonoid glycoside, mearnsetin 3-<i>O</i>-<i>α</i>-L-arabinopyranoside (<b>4</b>), were discovered, and the absolute configuration of the known compound, myrsinoic acid B (<b>5</b>), was re-established. To ensure the structural accuracy of these compounds, comprehensive spectroscopic analyses were performed, including one- and two-dimensional nuclear magnetic resonance spectroscopy, mass spectrometry, and circular dichroism spectroscopy. In addition, computational analysis methods such as density functional theory (DFT)-based Electronic Circular Dichroism (ECD) simulations and Gauge-Including Atomic Orbitals (GIAOs) ¹H and ¹³C NMR chemical shift calculations with DP4+ probability analysis were utilised to further support the structural assignments.