Antiproliferative activity of New Zealand propolis and phenolic compounds vs human colorectal adenocarcinoma cells.

New Zealand propolis is a "European" type propolis obtained by honey bees mainly from exudates of poplar. European type propolis is known to have anti-inflammatory and anti-cancer properties and this activity has been attributed to some of the main constituents such as chrysin and CAPE (caffeic acid phenethyl ester). As part of our studies on how New Zealand propolis might benefit gastro-intestinal health, we carried out in vitro bioactivity-guided fractionation of "Bio30™" propolis using both anti-inflammatory (TNF-α, COX-1, COX-2) and anti-colon cancer (DLD-1 colon cancer cell viability) assays; and determined the phenolic compounds responsible for the activity. The New Zealand wax-free Bio30™ propolis tincture solids had very high levels of the dihydroflavonoids pinocembrin and pinobanksin-3-O-acetate, and high levels of the dimethylallyl, benzyl and 3-methyl-3-butenyl caffeates relative to CAPE. The DLD-1 assays identified strong anti-proliferative activity associated with these components as well as chrysin, galangin and CAPE and a number of lesser known or lower concentration compounds including benzyl ferulate, benzyl isoferulate, pinostrobin, 5-phenylpenta-2,4-dienoic acid and tectochrysin. The phenolic compounds pinocembrin, pinobanksin-3-O-acetate, tectochrysin, dimethylallyl caffeate, 3-methyl-3-butenyl caffeate, benzyl ferulate and benzyl isoferulate also showed good broad spectrum activity in anti-proliferative assays against three other gastro-intestinal cancer cell lines; HCT-116 colon carcinoma, KYSE-30 oesophageal squamous cancer, and NCI-N87 gastric carcinoma. Activity is also observed in anti-inflammatory assays although it appears to be limited to one of the first cytokines in the inflammatory cascade, TNF-α.