Antifungal Phenols from <i>Woodfordia uniflora</i> Collected in Oman

Abstract

<i>Woodfordia uniflora</i> is a flowering shrub unique to the Dhofar region of Oman and is used locally as a sedative and remedy for skin infection. However, no study to date has examined the pharmacological properties of this plant, and studies regarding phytochemicals present in <i>W. uniflora</i> are limited. Herein, phytochemical screening of the extract of <i>W. uniflora</i> was performed using LC/MS. Three new phenolic compounds, (±)-woodfordiamycin (<b>1</b>), woodfordic acid (<b>2</b>), and rhamnetin 3-<i>O</i>-(6″-galloyl)-β-d-glucopyranoside (<b>3</b>), together with 16 known compounds <b>4</b>-<b>19</b>, were isolated from the antifungal fraction of the extract. The structures of the new compounds were established by NMR and HR-MS data, and their absolute configurations were established using chemical transformations, including Mosher's method, comparison of experimental and calculated electronic circular dichroism data, and gauge-including atomic orbital NMR chemical shift calculations, followed by DP4+ analysis. The isolated compounds (<b>1</b>-<b>19</b>) were tested for antifungal activity against human fungal pathogens <i>Cryptococcus neoformans</i> and <i>Candida albicans</i>. Compounds (±)<b>-1</b> and <b>8</b> showed antifungal activity against <i>C. neoformans</i>, with the lowest minimum inhibitory concentrations of 1.8-1.9 μM, which was ∼10-fold lower than that of the currently available antifungal drug fluconazole, while (±)<b>-1</b>, <b>8</b>, and <b>19</b> showed antifungal activity against <i>C. albicans</i>.