UPLC Rapid Quantification of Ascorbic Acid in Several Fruits and Vegetables Extracted Using Different Solvents

Chinchkar A, Singh A, Upadhyay A, Mehari B. Ultrasonic-assisted extraction and UHPLC determination of ascorbic acid, polyphenols, and half-maximum effective concentration in Citrus medica and Ziziphus spina-christi fruits using multivariate experimental design

This study aimed to determine the concentrations of ascorbic acid and polyphenols in fruits and peels of Citrus medica and Ziziphus spina-christi grown in Ethiopia. Conditions of ultrasound-assisted extraction (UAE) and ultra-high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) were optimized, using a multivariate experimental design. The optimum conditions of UAE were 15 min extraction time at 35 ℃, with 75 % aqueous methanol as solvent, and a fruit powder-to-solvent ratio (m/v) of 1:15. Among the different drying conditions investigated, freeze-drying was found to be appropriate for analyzing ascorbic acid, polyphenols, and antioxidant potential. The overall ranges, across the fruits and peels, of ascorbic acid, total polyphenols, and antioxidant potentials (EC50) obtained were 8.7 ± 1.4-91.2 ± 2.6 mg/100 g, 253.0 ± 6.3-764.1 ± 25.8 mg GAE/100 g and 2.4 ± 0.1-26.1 ± 2.9 mg/mL, respectively. This indicates that the fruits and peels of the studied plants are advantageous as sources of ascorbic acid and polyphenols.

A Simple, Cost-Effective, and Green HPTLC Method for the Estimation of Ascorbic Acid in Solvent and Ultrasound-Assisted Extracts of Phyllanthus emblica, Capsicum annuum, and Psidium guajava

Greener analytical methodologies for the estimation of ascorbic acid (AA) are poorly reported in the literature. Furthermore, the green indexes of the literature’s analytical assays of AA estimation have not been assessed. As a consequence, the aim of this research is to invent and validate a simple, cost-effective, and green reverse-phase “high-performance thin-layer chromatography (HPTLC)” method for the estimating AA in the solvent extracts (SE) and ultrasound-assisted extracts (UAE) of Phyllanthus emblica, Psidium guajava, and Capsicum annuum. The greener mobile phase for AA estimation was a binary mixture of water and ethanol (70:30, v/v). At a wavelength of 265 nm, the detection of AA was carried out. The greener HPTLC technique was linear in the 25–1200 ng/band range. In addition, the method was simple, cost-effective, accurate, precise, robust, sensitive, and green. The amount of AA was highest in the SE and UAE of P. emblica compared to the SE and UAE of P. guajava and C. annuum. The amount of AA in the SE of P. emblica, P. guajava, and C. annuum was found to be 491.16, 168.91, and 144.30 mg/100 g, respectively. However, the amount of AA in the UAE of P. emblica, P. guajava, and C. annuum was found to be 673.02, 218.71, and 199.30 mg/100 g, respectively. Using the “analytical GREEnness (AGREE)” methodology, the greenness index for the developed method was calculated to be 0.88, showing that the developed method has an excellent green profile. When it came to extracting AA, the UAE method outperformed the SE method. These findings suggested that the developed method might be used to estimate the AA in a variety of vegetable crops, plant-based extracts, and commercial formulations. Furthermore, because of the use of greener solvent systems against the commonly utilized hazardous solvent systems for AA determination, this technique is also safe and sustainable.

Direct analysis of ascorbic acid in food beverage samples by flow injection analysis using reduced graphene oxide sensor

In this paper, a simple, sensitive and precise electroanalytical method was developed using flow injection analysis (FIA) with amperometric detection and reduced graphene oxide sensor for ascorbic acid determination in samples of multivitamin beverages, milk, fermented milk, and milk chocolate. The advantages of this sensor include a potential displacement of 450 mV and a 2-fold peak current increase for electrochemical oxidation of ascorbic acid, which resulted in a highly sensitive method. No interference of sample matrix was observed, avoiding solvent extraction procedures (samples were only diluted). The FIA allowed a high analytical frequency, approximately 96 injections per hour, together with adequate detection limit of 4.7 μmol L^-1. Good precision (RSD < 7%) and accuracy (recoveries between 91 and 108%) evidenced the robustness of the method. The method was compared with ultra-fast liquid chromatography (UFLC) obtaining statistically similar results (95% confidence level). The ascorbic acid content in samples varied from 0.065 to 2.53 mmol L^-1.