Isolation and chemical characterization of secondary metabolites from Gazania rigens and their antimicrobial and cytotoxic activities

Abstract

Phytochemical study of Gazania rigens whole plant led to isolation and structural characterisation of six known compounds including lupeol (1), lupenone (2), β-sitosterol 3-O-β-glucopyranoside (3), dunalianoside D (4), 3,5-di-O-caffeoylquinic acid (5), and tachioside (6). Compounds (1–4, and 6) 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 in vitro antimicrobial activity against various bacterial and fungal strains. Only lupeol (1) exhibited a moderate antibacterial activity against K. pneumoniae with IC₅₀ value of 19.05 µg/mL. The cytotoxic potential of the total ethanol extract and its derived fractions of G. rigens was evaluated against the MDA-MB-468 TNBC cell line using MTT assay. The petroleum ether, EtOAc and n-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.

Graphical Abstract

Keywords:

• Asteraceae
• Gazania rigens
• phytoconstituents
• antimicrobial
• cytotoxicity

Acknowledgments

The authors are grateful to the Egyptian Government and the National Center for Natural Products Research, School of Pharmacy, University of Mississippi, USA, for financial support. We are also thankful to Dr. Bharathi Avula and Dr. Siddharth Kaushal Tripathi for doing HR-ESI-MS and antimicrobial assay, respectively.

Disclosure statement

All authors declare that they have no conflict of interest.

Additional information

Funding

This work did not receive any fund.