Extraction and Characterization of Phenolic Acid Compounds of Zahidi and Khastawi Dates Seed Extract and Evaluation of their Antibacterial Activity.

Abstract

Background: The date fruit is a remarkable source of nutraceuticals and bioactive compounds. Different types of phenolic compounds with high antioxidant capacity are found in date seed extract. Additionally, these compounds can be potential antibacterial agents to combat antibiotic resistance strains. Therefore, the main idea of the current study was to quantify five key phenolic acids in the ethanolic extract of Zahidi and Khastawi dates seed and to examine their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA).

Methods: The concentration of gallic acid, ferulic acid, p-coumaric acid, sinapic acid and cinnamic acid in the seed extracts were determined by high performance liquid chromatography (HPLC). Then, antibacterial activity of date seed extracts was analyzed using well diffusion method. Furthermore, a scanning electron microscopy (SEM) analysis was performed to confirm the antibacterial effects of the seed extracts.

Results: Phenolic acids were found to be in the range of 10.59 to 33.65 µg mg^-1 in Zahidi and 13.69 to 41.56 µg mg^-1 in Khastawi date seed extract. Gallic acid was the dominant phenolic acid, while cinnamic acid was seen in the lowest concentrations compared with the other phenolic acids in both cultivars. Antibacterial activity study showed that the growth inhibition effect of Khastawi date (14±0.21 mm) was higher than that of Zahidi date (8±0.13 mm) against MRSA. As well, the maximum DPPH scavenging percentage was 79% and 62% for the Khastawi and Zahidi date seed extracts, respectively. Also, SEM analysis suggested that treatment of MRSA with date seed extract resulted in a significant disruption of bacterial structure.

Conclusion: It can be concluded that date seed extract can be considered as a potential source of antibacterial compounds for the drug discovery purposes.