Biochanin A similarly influences the fluidity of liposomes formed from charged and zwitterionic lipids.

Biochanin A is a naturally occurring isoflavone, most commonly found in legumes, especially in soya beans or in red clover. The spectrum of biochanin As biological activities is very wide: it displays antioxidative, cardioprotective, anti-inflammatory, anticancer and enzyme inhibitory properties. At least some of those activities may involve the interaction of biochanin A with the lipid phase of membranes. A recent study was performed to characterise the interactions of biochanin A with liposomes formed from different lipids. The influence of biochanin A on the fluidity of liposome membranes was studied by means of (DPH) fluorescence polarisation measurements. Liposomes prepared from egg yolk phosphatidylcholine (EYPC), bovine brain phosphatidylserine (BBPS), dipalmitoyl phosphatidylcholine (DPPC) and dimyristoyl:phosphatidylcholine (DMPC), phosphatidylglycerol (DMPG), and phosphatidylethanolamine (DMPE). The set of lipids used enabled us to follow the effects of biochanin A on both the gel and liquid crystalline states of the lipid bilayer as well as on zwitterionic or charged lipids. For all the lipids under study, we observed a concentration-dependent decrease in DPH fluorescence intensity induced by biochanin A. The fluorescence polarisation degree was significantly increased by the presence of the studied isoflavone in liposomes composed of lipids (EYPC, DMPC, DMPG, BBPS) which were in the liquid crystalline state under the experimental conditions (room temperature). Almost no changes in the DPH polarisation degree were observed for mixtures of biochanin A with DPPC and DMPE ' lipids which are in the gel state at room temperature. No changes in DPH polarisation were seen even when isoflavone/DPPC liposome suspensions were prepared at temperatures above the gel-liquid crystalline phase transition and subsequently measured at room temperature. Comparing the relative polarisation alterations induced by biochanin A in different lipids, we may conclude that bilayers composed of charged DMPG and all zwitterionic lipids were rigidified by the presence of biochanin A to the same extent, while BBPS bilayers were less altered by isoflavone.