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Objectives This study investigated the chemical composition and the antioxidant and antimicrobial activities of the essential oil isolated from the aerial parts of Citrus aurantifolia L. Methods Fresh Citrus aurantifolia L. leaves were collected from farms in Sur city, located in the Al-Sharqia (Eastern) region of the Sultanate of Oman, during June–July of 2015. The essential oil was isolated using hydrodistillation. Gas chromatography–mass spectrometry (GC–MS) was used to identify and quantify the chemical constituents of the oil. An in-vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging method was used to determine the antioxidant activity of the isolated oil from the lime leaves while a disc diffusion method was used to evaluate the antibacterial activity against Gram-negative and Gram-positive bacteria. Results Thirty-three chemical compounds were identified, with d -limonene (63.35%) forming the major constituent. Other prominent constituents include 3,7-dimethyl-2,6-octadien-1-ol (7.07%), geraniol (6.23%), E -citral (4.35%), Z -citral (3.29%), and β-ocimene (2.25%). The essential oil of Citrus aurantifolia L. leaves showed excellent antibacterial activity against Staphylococcus aureus and moderate activity against pathogenic Escherichia coli strains. The oil exhibited promising in-vitro antioxidant activity (IC 50 value = 21.57 μg/mL) but showed moderate antibacterial activities. Conclusions The essential oil from Omani lime leaves is characterized by a high d -limonene content, making it useful for food, pharmaceutical, and perfumery industries.

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The pigment content in microalgae is a specific feature of each species. Pigments from natural sources are gaining more importance mainly due to health and environmental issues. Algae contain a wide range of pigments. Three major classes of pigments are chlorophylls, carotenoids (carotenes and xanthophylls) and phycobilins (Phycocyanin and phycoerythrin). Phycocyanin and phycoerythrin belong to the major class of phycobilins photosynthetic pigment while fucoxanthin and peridinin belong to carotenoid group of photosynthetic pigment. Macro-and microalgae (including cyanobacteria) have been recognized to provide a wide diversity of metabolites including pigments for energy capture and photo-protection.