Antioxidant and Antibacterial Activities of Jasminum officinale L. f. var. grandiflorum (L.) Kob. Leaf Extracts

Abstract

The investigation of phytochemicals and their effects on plants is currently receiving significant attention due to the well-known fact that plants contain secondary metabolites that have high levels of usefulness in various applications. These applications include food additives, biopesticides, and pharmaceuticals. In a recent study, we thoroughly examined the total phenolic content (TPC), and the antioxidant, and antibacterial properties of Jasminum officinale L.f. var. grandiflorum (L.) Kob. (also known as Spanish jasmine) leaf extracts, providing valuable insights into its potential benefits. Our study performed a crude methanol (ME) extraction of Spanish jasmine leaves with acid-base solvent partitioning, resulting in an acidic fraction (AE), a neutral fraction (NE), and an aqueous fraction (AQ). The Folin-Ciocalteu method was used to determine the TPC of the extracts. The AE fraction displayed the highest TPC (79.8±0.61 mgGAE/g dry weight), followed by the NE and AQ fractions. The extracts were further evaluated for their antioxidant activity using the DPPH assay. The AE fraction had the highest antioxidant activity with an EC50 value of 4.6±0.40 µg/mL. The main active compound, oleuropein, was isolated and determined using spectral data. The isolated compound displayed excellent antioxidant activity with an EC50 value of 13.0±0.06 µg/mL. Moreover, the antibacterial activity of the Spanish jasmine leaf extracts was calculated using the disc diffusion method based on the minimum inhibitory concentration. The AE fraction exhibited activity against the Gram-negative bacteria, Vibrio parahaemolyticus, with a MIC value of 0.78 µg/mL. The AE fraction also displayed the highest degree of activity against Staphylococcus strains, including drug-resistant strains (MRSA and VRSA), with a MIC range of 0.39-12.5 µg/mL. It is important to highlight that the AE fraction demonstrated the highest level of activity against all VRSA strains tested despite their resistance to vancomycin and oxacillin. These findings strongly indicate that Spanish jasmine leaves possess potent natural antioxidant and antibacterial properties, positioning them as a highly promising plant source.