Antioxidant, antitubercular and cytotoxic activities of Piper imperiale

Phenolic compounds are widely distributed in Nature and act as pharmacologically active constituents in many herbal medicines. They have multiple biological properties, most notably antioxidant, antibacterial and cytotoxic activities. In the present study an attempt to correlate the phenolic composition of leaf, flower and wood extracts of Piper imperiale, with antioxidant, antitubercular and cytotoxic activities was undertaken. The total phenol content ranged from 1.98 to 6.94 mg GAE/gDW among ethanolic extracts, and gallic acid, catechin, epicatechin, ferulic acid, resveratrol and quercetin were identified and quantified by HPLC. DPPH and ABTS assays showed high antioxidant activity of the leaf extract (EC(50ABTS) = 15.6 µg/mL, EC(50DPPH) = 27.3 µg/mL) with EC₅₀ in the same order of magnitude as the hydroxyquinone (EC(50ABTS) = 10.2 µg/mL, EC(50DPPH) = 15.7 µg/mL). The flower extract showed strong antimicrobial activity against Mycobacterium tuberculosis H₃₇Rv. All the extracts exhibited dose-dependent cytotoxic effects against MCF-7 cancer cells. This is the first time that a Piper extract has been found to be highly active against M. tuberculosis. This study shows the biological potential of Piper imperiale extracts and gives way to bio-guided studies with well-defined biological activities.