Phloroglucinol Benzophenones and Xanthones from the Leaves of Garcinia cowa and Their Nitric Oxide Production and α-Glucosidase Inhibitory Activities

Abstract

Five new compounds-two phloroglucinol benzophenones, garciniacowones F (<b>1</b>) and G (<b>2</b>), and three xanthones, garciniacowones H (<b>3</b>), I (<b>4</b>), and J (<b>5</b>)-together with seven known xanthones (<b>6</b>-<b>12</b>) were isolated from the fresh leaves of <i>Garcinia cowa</i>. Their structures were elucidated by detailed analysis of NMR and MS data. Compounds <b>1</b> and <b>2</b> are phloroglucinol benzophenones containing a polyprenylated bicyclo[3.3.1]nonane ring system, while compounds <b>3</b>-<b>5</b> are rare xanthones having farnesyl (<b>3</b> and <b>5</b>) and geranylgeranyl (<b>5</b>) units at C-8. Compounds <b>1</b>, <b>3</b>, <b>4</b>, <b>7</b>, <b>8</b>, and <b>10</b> exhibited inhibitory effects on NO production in LPS-induced RAW264.7 macrophage cells with IC₅₀ values ranging from 5.4 to 18.6 μM. Compounds <b>4</b> and <b>8</b> had α-glucosidase inhibitory activities with IC₅₀ values of 15.4 and 11.4 μM, respectively, which were more potent than that of the acarbose control.