Abstract

PHARMACOLOGICAL EVALUATION OF MARINE MACROALGAE FROM YEMENI COASTAL WATERS: EXPANDED INVESTIGATION INTO THEIR ANTIMICROBIAL AND ANTIOXIDANT ACTIVITIES

Amina El-Shaibany, Mahmoud Mahyoob Alburyhi*, Mursal Ali Aoun and Hanan Abdullah Ghallab

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Abstract

Background: Marine macroalgae are rich sources of secondary metabolites with potential as natural therapeutics against antimicrobial resistance (AMR) and oxidative stress-related diseases. Yemeni coastal waters, an underexplored region, harbor unique algal species with uncharacterized pharmacological potential. Objective: This study evaluates the antimicrobial and antioxidant activities of four macroalgal species—Sargassum muticum, Padina australis, Taonia atomaria, and Codium reediea—from the Red Sea coast of Al- Hudaida, Yemen, and assesses their phytochemical profiles. Methods: Algae collected in December 2020 underwent methanolic extraction. Antimicrobial activity was tested via agar disc diffusion against five human pathogens. Antioxidant capacity was measured using the DPPH radical scavenging assay. Thin-layer chromatography (TLC) identified flavonoids, tannins, and related compounds. Results: Codium reediea showed strong antimicrobial activity against Staphylococcus aureus (19 mm inhibition zone). All extracts had limited efficacy against Escherichia coli, indicating Gram-negative resistance. Padina australis exhibited the highest antioxidant activity (IC₅₀ = 113 μg/mL). TLC confirmed flavonoids and tannins in all extracts. Conclusion: Yemeni macroalgae are promising candidates for antimicrobial and antioxidant drug development. Their unique metabolite profiles, shaped by high salinity and UV exposure, warrant further bioassay-guided and metabolomic studies.

Keywords: Marine macroalgae, antimicrobial activity, Antioxidant potential, Yemeni Red Sea coast, Phytochemical screening.