Effect of acidless orange on P-glycoprotein function

Abstract

Keywords: Sweet orange; Polymethoxyflavones; P-glycoprotein; Drug efflux

Objectives: This study was performed to evaluate the potential role of green acidless orange as a P-glycoprotein (P-gp) modulator.

Methods: Squeezed juice from green acidless orange was extracted by subjecting to amberlite XAD-16 column and eluted with methanol and acetone. Methanol and acetone extracts were combined and evaporated to dryness to obtain crude extract. The dried crude extract was then partitioned between dichloromethane and water. The dried dichloromethane extract was applied to silica gel PF254 column chromatography to isolate active ingredients. The effect of crude extract on digoxin transport was studied in Caco-2. The effects of isolated polymethoxyflavones on calcein-AM (CAM) accumulation were examined in overexpressed human P-gp cell line, LLC-GA5-COL300, compared with that of LLC-PK₁.  

Results: Crude extract of green acidless orange significantly decreased the efflux ratio of digoxin transport across Caco-2 monolayer from 25.2 to 6.1 times, suggesting that this citrus may inhibit P-gp function. The active ingredients were elucidated as polymethoxyflavones including 5,6,7,3’,4’-pentamethoxyflavone (sinensetin), 3,5,6,7,3’,4’-hexamethoxyflavone (quercetagetin hexamethyl ether), and 3,5,6,7,8,3’,4’-heptamethoxyflavone. All three polymethoxyflavones obviously increased CAM accumulation in LLC-GA5-COL300 in a concentration-dependent manner. 3,5,6,7,8,3’,4’-heptamethoxyflavone found in this citrus fruit demonstrated the most potent effect on human P-gp function.

Conclusion: Taken together, the results from this study indicate that acidless orange could inhibit P-gp function. The active ingredients were elucidated to be polymethoxyflavones.