The determination of certain phenolic acids employing a gradient HPLC method is described, in this study. The analysis was performed by using a gradient program with the two solvents system (A: methanol:water:formic acid (10∶88∶2 v/v); B: methanol:water:formic acid (90:8:2 v/v)). The flow rate of 1 mL · min⁻¹, injection volume of 10 µL was used and signals were detected at 280 nm. Propylparaben was a suitable compound as an internal standard for this system. The method was validated and highly repeatable (between RSD values of 0.35–1.65) and linear results were obtained. The LOD and LOQ values of the phenolic acids are in the range of (2.58×10⁻⁶−9.69×10⁻⁶ M) and (7.83×10⁻⁶−2.93×10⁻⁵ M), respectively. The applicability of the method was tested by using some plant source materials, and the phenolic acid contents were successfully determined via well‐defined peaks. Therefore, the progressed method is suggested for the quantification of phenolic acids in food industry and laboratories.

Context: Morus nigra L. (Moraceae) has various uses in traditional medicine. However, the effect of M. nigra on cognitive impairment has not been investigated yet. Objective: The objective of this study is to determine the phenolic acid content and DNA damage protection potential of M. nigra leaf extract and to investigate the extract effect on cognitive impairment and oxidative stress in aging mice. Materials and methods: Phenolic acid content was determined by quantitative chromatographic analysis. DNA damage protection potential was evaluated on pBR322 plasmid DNA. Thirty-two Balb-C mice were randomly divided into four groups (control, d-galactose, d-galactose + M. nigra 50, and d-galactose + M. nigra 100). Mice were administered d-galactose (100 mg/kg, subcutaneous) and M. nigra (50 or 100 mg/kg, orally) daily for 8 weeks. Behavioral responses were evaluated with Morris water maze. Activities of antioxidant enzymes and levels of malondialdehyde (MDA) were assayed in serum, brain, and liver. Results: In extract, vanillic (632.093 μg/g) and chlorogenic acids (555.0 μg/g) were determined. The extract between 0.02 and 0.05 mg/mL effectively protected all DNA bands against the hazardous effect of UV and H₂O₂. Morus nigra significantly improved learning dysfunctions (p < 0.01), increased memory retention (p < 0.01), reduced MDA levels (p < 0.05), and elevated SOD, GPx, and CAT activities (p < 0.05) compared with the d-galactose group. Discussion and conclusion: These results show that M. nigra has the potential in improving cognitive deficits in mice and that M. nigra may be useful to suppress aging, partially due to its scavenging activity of free radicals and high antioxidant capacity.