Convolvulus austroaegyptiacus Abdallah & Sa'ad (CA) and Convolvulus pilosellifolius Desr. (CP) are commonly used in the Saudi Arabia folk medicine. They are potent in treating the ulcers and skin diseases. The lack of information about their biological activities led us to investigate the possible biological activities by determination of antibacterial and antioxidant activities of total ethanolic extracts and various fractions. Total flavonoid contents of the plants were determined by colorimetric method while total phenols were determined by using Folin-Ciocalteu method. In vitro antibacterial activity was studied against E. coli, P. aeruginosa, and B. subtilis, and the total antioxidant capacity was evaluated by radical scavenging method. IC50 were found to be 21.81, 17.62, and 3.31 μg/mL for CA, CP, and vitamin C, respectively, while the lowest MIC value of 0.25 mg/mL was recorded with CP extract against B. subtilis. Around 21 compounds are tentatively elucidated from both plants using rapid, simple, and high-resolution analytical technique for chemical profiling of natural compounds by direct analysis in real-time of flight-mass spectrometry, of which 17 were not isolated or reported previously.
A number of new [(4-methyl-2-oxo-2H-chromen-7-yl)amino]methylcoumarins (5a-c), benzofuran (6), and benzoxazol (7) were synthesized through the reaction of 7-amino-4-methylcoumarin (1) with a number of organic halides. In addition, series of N-substituted 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetohydrazide (11a-h) and (12a-d) were prepared from the reaction of 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetohydrazide (8) with corresponding heteroaryl/alkyl halides (2-4, 9, and 10). The synthesized compounds were characterized by elemental analysis and by spectroscopic techniques such as 1 H-NMR, 13 C-NMR, and mass spectrometry and were tested for their in vitro antimicrobial activity. The newly synthesized compounds exerted significant inhibitory activity against the growth of tested bacterial strains and a few of them are found to be potent antimicrobial agents.
A simple, rapid, and sensitive high-performance liquid chromatography (HPLC) method was developed and validated for identification and determination of flavonoids in Convolvulus pilosellifolius. The chromatographic separation was achieved in less than 6 min using C18 column (150 × 4.6 mm, 3 μm) with isocratic mixture of methanol and water containing 0.1 percent v/v formic acid in the ration of 80:20 at 258 nm with a flow rate of 0.4 mL/min. The method was validated in the linear calibration curve ranged between 1 and 300 μg/mL with detection limits of 0.39 and 0.26 μg/mL and quantification limits of 1.20 and 0.79 μg/mL for quercetin and kaempferol, respectively. Good repeatability of the method were achieved at percent relative standard deviation (RSD < 2.18 percent) with respect to inter-and intraday repeatability. Recovery values were found to be in the range of 98.2-100.2 percent, indicating high accuracy of the method. The maximum flavonoid contents were 1.07 and 1.54 percent for quercetin and kaempferol, respectively.
Recently, chromatographic techniques have the potential to be greener in order to reduce the environmental impact. In this work, a new simple, sensitive, efficient, and green analytical method based on UHPLC-MS has been developed for a quick determination of methylxanthines including caffeine, theobromine, and theophylline in tea. Under the optimum conditions, a baseline separation has been achieved within 30 seconds, using isocratic elution consisting of 90% water and only 10% acetonitrile at 0.5 mL/min flow rate (3 mL acetonitrile per hour). The mass spectrometer was operated with the SIR mode in ESI+. The developed method was found to be linear in the range of 0.03–5 μg/mL, with correlation coefficients greater than 0.9995 for the three compounds. The respective values of LOD were found to be 0.025, 0.015, and 0.01 μg/mL for caffeine, theobromine, and theophylline, respectively. The proposed assay was applied to 30 commercial tea samples of different brands. Both caffeine and theobromine were found in all tea samples with maximum concentration in sample no. 15, corresponding to 32.6 and 2.72 mg/g of caffeine and theobromine, respectively. On the contrary, theophylline was not detected at all in most samples. When compared with all previous studies that dealt with the same compounds in different matrices, the developed method was found to be the fastest, allowing high-throughput analyses with more than 100 samples/h. The results prove that the method is suitable for routine analysis of methylxanthines and to distinguish the quality of tea samples of various brands.
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