Many type B polycyclic polyprenylated acylphloroglucinols (PPAPs) bear a lavandulyl-derived substituent, and the configurational assignment of this side chain can be difficult and sometimes leads to erroneous conclusions. In this study, 21 PPAPs, including the new xanthochymusones A-I (<b>1</b>-<b>9</b>), have been isolated from the fruits of <i>Garcinia xanthochymus</i> and structurally characterized. The relative configuration of the C-30 stereocenter was assigned by a combination of chemical transformations, <sup>1</sup>H-<sup>1</sup>H coupling constants, conformational analysis, and NOE experiments. The configurational assignment of compound <b>7</b> indicates that the relative configuration at C-30 of PPAPs is not always the same. The absolute configurations of the new compounds were assigned by ECD and X-ray diffraction data, as well as by biosynthetic considerations. Analysis of NMR data enabled the configurational revision of garcicowins C and D. All the isolated PPAPs were tested for antiproliferative activity against three human hepatocellular carcinoma cell lines, including Huh-7, Hep 3B, and HepG2. Compounds <b>5</b> and <b>6</b>, 7-<i>epi</i>-isogarcinol (<b>16</b>), and coccinone C (<b>17</b>) exhibited moderate antiproliferative activity. Compounds <b>6</b> and <b>16</b> induced apoptosis and inhibited cell migration in Huh-7 cells, probably through downregulating the STAT3 signaling pathway. This study provides effective methods for configurational assignments of type B PPAPs.