Abstract
A fast and sensitive ultra-high performance liquid chromatography-photodiode array (UHPLC-PDA) method for simultaneous quantification of oleanolic acid (OA) and ursolic acid (UA) in plant materials was developed. A central composite design combined with a response surface methodology was utilized to establish optimal separation conditions. The final separation was accomplished on a Zorbax Eclipse XDB-C18 column (1.8 μm, 100 mm × 3 mm I.D., Agilent, Santa Clara, CA, USA) using a mixture 90:10 (v/v) of methanol and 1% (w/v) aqueous orthophosporic acid as a mobile phase at a flow rate of 0.44 mL/min and temperature of 18 °C. The analysis was completed in 6.2 min with satisfactory resolution of 1.5 between the target analytes. The developed method proved to be precise (relative standard deviations below 3.2%), accurate (recoveries in the range of 95.27%–98.60%), and sensitive (limits of detection (LODs) in the range of 0.047–0.051 mg/mL). The method was then successfully applied to evaluate OA and UA content in real samples of selected Ericaceae plant materials (leaves of Arctostaphylos uva ursi, Vaccinium myrtillus, Vaccinium vitis idaea, Gaultheria procumbens). The content of OA and UA in investigated samples varied in the range of 0.74–4.47 mg/g dry weight (dw) and 1.30–18.61 mg/g dw, respectively.
Highlights
Oleanolic acid (3β-3-hydroxyolean-12-en-28-oic acid, oleanolic acid (OA)) and ursolic acid (3β-3-hydroxyurs12-en-28-oic acid, UA) are two isomeric pentacyclic triterpenes (Figure 1) that are ubiquitous constituents of various medicinal and dietary plants [1]
The potent antimicrobial activity of both compounds has been demonstrated towards various bacterial strains including Escherichia coli—a common pathogen of urinary tract infection [3]
Solvents used in extraction of plant materials (Avantor Performance Materials, Gliwice, Poland) were of analytical grade
Summary
Oleanolic acid (3β-3-hydroxyolean-12-en-28-oic acid, OA) and ursolic acid (3β-3-hydroxyurs12-en-28-oic acid, UA) are two isomeric pentacyclic triterpenes (Figure 1) that are ubiquitous constituents of various medicinal and dietary plants [1]. Numerous studies have demonstrated their versatile biological properties with anti-inflammatory activity being the most important from phytotherapeutic point of view. As the underlying mechanism of this action, the suppression of immune cells and cytokines (TNF-α, IL-12, IL-6, interferon-γ) production either via inhibition of pro-inflammatory enzymes (elastase, cyclooxygenases, lipoxygenases, nitric oxide synthase) and NF-κB-regulated genes expression or direct cytokine receptor interactions has been proposed [1,2]. The potent antimicrobial activity of both compounds has been demonstrated towards various bacterial strains including Escherichia coli—a common pathogen of urinary tract infection [3]. OA and UA were found to modulate bacterial resistance to some antibiotics and produce in.
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