ABSTRACT

Aim: This study aimed to investigate the chemical transformation of the phenolic hydroxyl groups into less hydrophilic moieties and detect the impact of this transformation on the biological activities of natural coumarins.

Methodology: Two coumarins have been isolated from the seeds of Red Delicious and Granny Smith apples. The investigated biological activities included antioxidant, antiproliferative, antibacterial, and antifungal potentials. The antioxidant potential was tested by figuring the capacity of these derivatives to trap hydroxyl and DPPH radicals. The antiproliferative potential was tested by MTT photometric assay against eight cancer lines named HeLa, SK-OV-3, AR42J, MCF-7, AB12, KYSE-30, LC540, and AMN3. The antibacterial potential was visualized via a well-defined disc diffusion assay employing six common pathogenic bacterial strains: Escherichia coli, Salmonella typhi, Klebsiella pneumonia, Haemophilus influenzae, Shigella dysenteriae, and Pseudomonas aeruginosa. The antifungal potential was highlighted against three pathogenic fungi named Candida albicans, Aspergillus flavus, and Aspergillus niger by applying the same general assay.

Results: From the outcomes of the tested biological activities, it is indicated that the phenolic hydroxyl groups are involved in the antioxidant activity of the natural coumarins by donating their protons to trap the free radicals. Also, the antitumor activity of the natural coumarins can be attributed to their antioxidant activity. Besides, the antimicrobial activity of the natural coumarins is improved by covering their phenolic hydroxyl groups by methylation. This alkylation can be improved the lipophilicity and in turn, enhanced the penetration of the tested coumarins into the pathogens.

Conclusion: It could be concluded that the phenolic hydroxyl groups exert a beneficial effect on the antioxidant and antiproliferative activities of the tested natural derivatives and a detrimental role in their antimicrobial activity.

Keywords: Coumarins, Antioxidant, Antiproliferative, Antibacterial, Antifungal, Hydroxyl group, Chemical modification.