Prenylflavonoids in hops and beer may slow proliferation of prostate cancer cells.

Prenylflavonoids are a unique class of phytochemicals found in the cluster of flowers on a branch of the hop plant Humulus lupulus. These compounds are also found in beer, which represents the main dietary source of prenylflavonoids.

The prenylated chalcone xanthohumol and related flavanones have been evaluated to determine their effects on normal cells as well as on cancer cells. Scientists at The Ohio State University have been comparing the biological effects of various hop-based prenylflavonoids on prostate cancer cell lines.

In experiments, the researchers isolated xanthohumol from hop extracts. Isoxanthohumol (IX) was formed by the cyclization of purified xanthohumol. Then they prepared 8-prenylnaringenin (8PN) and 6-prenylnaringenin (6PN) synthetically from commercially available naringenin.

All of the compounds were processed to more than 99% purity using high-performance liquid chromatography (HPLC). The scientists then exposed human (LNCaP, PC3) and rat (AT6.3) prostate cancer cell lines to individual hop prenylflavonoids for 48 hours. The effects of these compounds on cell growth were determined in vitro using a colorimetric cell viability assay (MTS) and a manual cell counting technique--the trypan blue exclusion technique.

The two most potent compounds, xanthohumol and isoxanthohumol, inhibited the growth of all cell lines based on their dosage. The strongest response to all treatments was observed in LNCaP cells, where xanthohumol and isoxanthohumol significantly decreased cell growth by 49% and 50%, respectively. Also, 8-prenylnaringenin and 6-prenylnaringenin significantly inhibited cell growth.

This research indicates that phytochemicals derived from hops and found in beer can influence the growth of prostate cancer cells in vitro. Additional studies will investigate the range of biological processes that might be modulated by prenylflavonoids and the mechanisms through which they act in normal and malignant prostate cells.

Further information. Steven Schwartz, Department of Food Science and Technology, The Ohio State University, Parker Food Sciences Building, 2015 Fyffe Rd., Room 235, Columbus, OH 43210; phone: 614-292-2934; fax: 614-292-4233; email: schwartz.177@osu.edu.