Three New Iridoid Derivatives Have Been Isolated from the Stems of Neonauclea reticulata (Havil.) Merr. with Cytotoxic Activity on Hepatocellular Carcinoma Cells

Abstract

Three new iridoids, namely neonanin A (<b>1</b>), neonanin B (<b>2</b>) and neoretinin A (<b>3</b>), as well as twelve known compounds, 6-hydroxy-7-methyl-1-oxo-4-carbomethoxyoctahydrocyclopenta[<i>c</i>]pyran (<b>4</b>), 4-<i>epi</i>-alyxialactone (<b>5</b>), loganetin (<b>6</b>), loganin (<b>7</b>), phenylcoumaran-α'-aldehyde (<b>8</b>), cleomiscosin A (<b>9</b>), ficusal (<b>10</b>), balanophonin (<b>11</b>), vanillic acid (<b>12</b>), <i>p</i>-coumaric acid (<b>13</b>), <i>cis,trans</i>-abscisic acid (<b>14</b>), and <i>trans,trans</i>-abscisic acid (<b>15</b>) were isolated from the stems of <i>Neonauclea reticulata</i> (Havil.) Merr. These new structures were determined by the detailed analysis of spectroscopic data and comparison with the data of known analogues. Compounds 1⁻13 were evaluated using an in-vitro MTT cytotoxic assay for hepatocellular carcinoma (HCC) cells, and the preliminary results showed that ficusal (10), balanophonin (11), and <i>p</i>-coumaric acid (13) exhibited moderate cytotoxic activity, with EC₅₀ values of 85.36 ± 4.36, 92.63 ± 1.41, and 29.18 ± 3.48 µg/mL against Hep3B cells, respectively.