Chemical Composition of the Hazelnut Kernel (<i>Corylus avellana</i> L.) and Its Anti-inflammatory, Antimicrobial, and Antioxidant Activities

Abstract

The chemical composition of hazelnut kernels (<i>Corylus avellana</i> L.) and their COX-2 inhibitory, antimicrobial, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activities were investigated. Six previously undescribed indoleacetic acid glycosides, hazelnutins A-F (<b>1</b>-<b>6</b>), and five known compounds (<b>7</b>-<b>11</b>) were isolated from the hazelnut kernels. The structures of compounds <b>1</b>-<b>6</b> were successfully identified by high-resolution-electrospray ionization-mass spectrometry and NMR data, and their absolute configurations were established by electron-capture detector spectroscopy analyses in corporation with quantum chemical calculations. Furthermore, the absolute configurations of compounds <b>7</b> and <b>8</b> were unambiguously confirmed for the first time. Compounds <b>8</b>-<b>11</b> were discovered in hazelnut kernels for the first time. Compounds <b>1</b>-<b>5</b> inhibited COX-2 expression with inhibition rates ranging from 36.10 to 64.08%. Compounds <b>3</b>, <b>4</b>, and <b>8</b> could inhibit the proliferation of <i>Candida albicans</i>. Compound <b>11</b> exhibited potent antioxidant activity against ABTS and DPPH with IC₅₀ values of 11.22 and 13.21 μmol/L, respectively. Compounds <b>8</b> and <b>10</b> exhibited moderate antioxidant activity against ABTS.