Anticancer activities of proanthocyanidins from the plant Urceola huaitingii and their synergistic effects in combination with chemotherapeutics.

Phytochemical investigation of the stem of Urceola huaitingii resulted in the isolation of nine proanthocyanidins (1-9), including a new compound (9). Their chemical structures were determined by UV, (HR) ESI-MS, 1D-, 2D-NMR, and CD spectra in combination with chemical derivatization. Determination of the absolute configuration of proanthocyanidins were discussed, which suggested that positive Δε values at 245nm can be applied to determine the absolute configuration of them. In addition, anticancer activities of proanthocyanidins (1-9) and their synergistic anticancer effects in combination with chemotherapeutics were evaluated. The results showed that some proanthocyanidins, especially compound 7 possessing two doubly interflavonoid linkages, exhibited significant synergistic anticancer effects with some chemotherapeutics in multiple cancer cell lines.