Hepatoprotective amide constituents from the fruit of Piper chaba: Structural requirements,mode of action,and new amides

The 80% aqueous acetone extract from the fruit of Piper chaba (Piperaceae) was found to have hepatoprotective effects on d-galactosamine (d-GalN)/lipopolysaccharide-induced liver injury in mice. From the ethyl acetate-soluble fraction, three new amides, piperchabamides E, G, and H, 33 amides, and four aromatic constituents were isolated. Among the isolates, several amide constituents inhibited d-GalN/tumor necrosis factor-α (TNF-α)-induced death of hepatocytes, and the following structural requirements were suggested: (i) the amide moiety is essential for potent activity; and (ii) the 1,9-decadiene structure between the benzene ring and the amide moiety tended to enhance the activity. Moreover, a principal constituent, piperine, exhibited strong in vivo hepatoprotective effects at doses of 5 and 10 mg/kg, po and its mode of action was suggested to depend on the reduced sensitivity of hepatocytes to TNF-α.