Polyphenolic Profile of Callistemon viminalis Aerial Parts: Antioxidant, Anticancer and In Silico 5-LOX Inhibitory Evaluations

Abstract

Five new compounds <i>viz</i> kaempferol 3-<i>O</i>-(4″-galloyl)-<i>β</i>-d-glucopyranosyl-(1‴→6″)-<i>O</i>-β-d-glucopyranoside (<b>1</b>), kaempferol 3-<i>O</i>-<i>β</i>-d-mannuronopyranoside (<b>2</b>), kaempferol 3-<i>O</i>-<i>β</i>-d-mannopyranoside (<b>3</b>), quercetin 3-<i>O</i>-<i>β</i>-d-mannuronopyranoside (<b>4</b>), 2, 3 (S)- hexahydroxydiphenoyl]-d-glucose (<b>5</b>) along with fifteen known compounds were isolated from 80% aqueous methanol extract (AME) of <i>C. viminalis</i>. AME and compounds exerted similar or better antioxidant activity to ascorbic acid using DPPH, O₂^-, and NO inhibition methods. In addition, compounds <b>16</b>, <b>4</b>, and <b>7</b> showed cytotoxic activity against MCF-7 cell lines while <b>3</b>, <b>7</b> and <b>16</b> exhibited strong activity against HepG2. An in silico analysis using molecular docking for polyphenolic compounds <b>2</b>, <b>3</b>, <b>7</b>, <b>16</b> and <b>17</b> against human stable 5-LOX was performed and compared to that of ascorbic acid and quercetin. The binding mode as well as the enzyme-inhibitor interactions were evaluated. All compounds occupied the 5-LOX active site and showed binding affinity greater than ascorbic acid or quercetin. The data herein suggest that AME, a source of polyphenols, could be used against oxidative-stress-related disorders.