Research on the pharmacognostic characteristics, physicochemical properties and in vitro antioxidant potency of Rosa laxa Retz. flos

Rosa laxa Retz. is an unexplored Rosaceae plant in Xinjiang, China, and its flower is traditionally used in Kazak to treat the common cold, fever, and epileptic seizures and lessen the effects of aging. In the present study, the pharmacognostic profiles, physicochemical properties, phytochemical characteristics, and in vitro antioxidant potency of Rosa laxa Retz. flos (RLF) were presented. In the pharmacognostic evaluation of RLF, organoleptic characteristics, internal structures, and powder information were observed, and physicochemical parameters, including moisture content, ash, pH value, swelling degree, and extractives were examined. The quantitative analysis of the chemical composition of four different polar extracts of RLF showed that the aqueous part had the highest total triterpene acid, flavonoid, and polyphenol content (4.50 ± 0.04 mg/g, 50.56 ± 0.03 mg/g, and 60.20 ± 0.09 mg/g, respectively). A high-performance liquid chromatography (HPLC)-diode array detector (DAD) method was established and the contents of gallic acid, ellagic acid, astragalin, and tiliroside in RLF were determined simultaneously. In the set concentration range, the linear relationship among the four components was good (r > 0.999), the average recoveries were 97.36%–100.54%. The contents of gallic acid, ellagic acid, astragalin, and tiliroside in RLF samples were (9.46 ± 2.31) mg/g, (10.60 ±0.75) mg/g, (1.13 ± 2.50) mg/g, and (1.11 ± 2.65) mg/g, respectively. The types of its secondary metabolites were determined by fluorescence, color reaction by chemical solvent method, and ultraviolet–visible (UV–Vis) spectroscopy. The functional groups of its secondary metabolites were determined by Fourier transform infrared (FTIR) spectroscopy. Results showed that RLF contains a variety of secondary metabolic products, including flavonoids, phenolic acid, glycoside, and organic acid. TLC identification showed it contains ursolic acid, β-sitosterol, tiliroside, astragalin, isoquercitrin, kaempferol-3-O-rutinoside, gallic acid, and ellagic acid. The in vitro antioxidant activity of different polar parts of RLF was investigated by DPPH, ABTS, and reduction performance experiments. The aqueous extract had the strongest antioxidant capacity, consistent with the high content of triterpene acids, flavonoids, and polyphenolic compounds. These findings will provide critical information for the study of quality standards and medicinal value of RLF and its extracts, justify its usage in traditional medicinal systems, and encourage the use of this plant in disease prevention and treatment. Its phytochemical composition and pharmacological studies need to be explored in future.

Research Highlights

• Optical microscope and scanning electron microscope (SEM) were used to observe the morphology, and microstructure of Rosa laxa Retz. flos (RLF).
• The physicochemical properties, fluorescence and phytochemical composition of four different polar extracts of RLF were analyzed by UV–Vis and FTIR.
• Determination of total triterpenic acid, total flavonoids, and total polyphenols in four different polar extracts of RLF by UV spectrophotometry.
• A high-performance liquid chromatography (HPLC)-diode array detector (DAD) method was established and the contents of gallic acid, ellagic acid, astragalin, and tiliroside in RLF were determined simultaneously. TLC confirmed that RLF contains ursolic acid, β-sitosterol, tiliroside, astragalin, isoquercitrin, kaempferol 3-rutinoside, gallic acid, and ellagic acid.
• The in vitro antioxidant activity of RLF was studied by DPPH, ABTS, and reducing ability experiments.