Identification of phenolic content, antibacterial and antioxidant activities of Lonicera caucasica PALLAS subsp. orientalis leaves

Abstract

Phenolic compounds, which are a prevalent type of secondary metabolite, are responsible for the antioxidant and antimicrobial properties found in the extracts. To contribute new knowledge to scientific literature, it is essential to study the phenolic content and bioactivity of plant parts that have not been previously studied or are unknown. Lonicera caucasica PALLAS subsp. orientalis is an endemic species that grows in a few cities in Türkiye. The study involved extracting L. caucasica leaves using methanol. The resulting fraction was then analyzed using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) to determine the phenolic content of the extract. The quantities of 22 out of the 67 phenolic compounds that were identified were determined. Among these, the top three in terms of quantity are chlorogenic acid, with a concentration of 2.223 ± 0.065 mg g-1, followed by quinic acid at 2.163 ± 0.057 mg g-1, and syringic acid at 1.192 ± 0.036 mg g-1. The antioxidant activities of the extracts were determined using the ABTS•+, DPPH (SC50, mg/mL) and FRAP (μM, TEAC) methods. The values were calculated to be 0.0135 ± 0.0001, 0.0136 ± 0.0001, and 2368.88 ± 2.94, respectively. Furthermore, the extracted substance was subjected to tests against three gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella aerogenes, and Escherichia coli) and three gram-positive bacteria (Enterococcus faecalis, Bacillus megaterium, and Streptococcus pyogenes). The outcomes of the tests were documented. The highest level of antibacterial activity was found to be against P. aeruginosa. Based on the findings, it has been determined that the leaves of L. caucasica contain a considerable amount of phenolic content, exhibit exceptional antioxidant activity, and display a strong antibacterial effect.