Isolation and chemical characterization of secondary metabolites from <i>Gazania rigens</i> and their antimicrobial and cytotoxic activities

Phytochemical study of <i>Gazania rigens</i> whole plant led to isolation and structural characterisation of six known compounds including lupeol (<b>1</b>), lupenone (<b>2</b>), <i>β</i>-sitosterol 3-<i>O</i>-<i>β</i>-glucopyranoside (<b>3</b>), dunalianoside D (<b>4</b>), 3,5-di-<i>O</i>-caffeoylquinic acid (<b>5</b>), and tachioside (<b>6</b>). Compounds (<b>1-4</b>, and <b>6</b>) were isolated for the first time. The structures of the isolated compounds were elucidated using different spectroscopic analyses such as ¹H,¹³C, and DEPT NMR analyses, besides HR-ESI-MS analysis. The isolated compounds and fractions were screened for <i>in vitro</i> antimicrobial activity against various bacterial and fungal strains. Only lupeol (<b>1</b>) exhibited a moderate antibacterial activity against <i>K. pneumoniae</i> with IC₅₀ value of 19.05 µg/mL. The cytotoxic potential of the total ethanol extract and its derived fractions of <i>G. rigens</i> was evaluated against the MDA-MB-468 TNBC cell line using MTT assay. The petroleum ether, EtOAc and <i>n</i>-BuOH fractions exhibited a moderate inhibitory action with IC₅₀ values of 22.42 ± 0.63, 25.55 ± 1.53, and 28.07 ± 0.63, respectively.