Antioxidative, phytochemical and antimicrobial analysis of juices of eight citrus cultivars grown in Pakistan

Comparative nutritional analysis of citrus varieties cultivated in Pakistan has not been reported. Citrus is consumed all over the world due to its taste and also has pharmacological components. The present investigation evaluated the antioxidant, reducing power, total flavonoids and phenolics, DPPH free radical scavenging, protein kinase inhibition, and the antimicrobial activities of eight Pakistani citrus varieties. Grapefruit showed maximum total antioxidant potential (77 µg AAE/100 mg), followed by Kinnow and Shakri. Khatai showed maximum reducing power potential (69.6 µg AAE/100 mg) while Shakri and Grapefruit trailed it. All the varieties showed significant DPPH free radical scavenging activity. Maximum total phenolics in citrus juice were found in Shakri and Kinnow; 26.2 and 25.9 µg GAE/100mg, respectively. Variation in total flavonoids content was observed as Kinnow>Grapefruit>Shakri>Khatai. All the citrus juices showed mild to moderate antibacterial activity, while Mosambi and Malta contained potent antifungal components. HPLC analysis of citrus juices revealed that catechin was present in all citrus genotypes except Kinnow. The study concludes that citrus juices contain strong antioxidative potential, bear protein kinase inhibitors and can be used as cancer chemoprevention and supportive nutrition.

The Grapefruit Flavonoid Naringenin Inhibits Multiple Cardiac Ion Channels

Drinking fresh grapefruit juice is associated with a significant prolongation of the QT segment on the electrocardiogram (ECG) in healthy volunteers. Among the prominent flavonoids contained in citrus fruits, the flavanone naringenin is known to be a blocker of the human ether-a-go-go related gene (hERG) potassium channel. We hypothesized that naringenin could interfere with other major ion channels shaping the cardiac ventricular action potential (AP). To this end, we examined the effects of naringenin on the seven currents comprising the Comprehensive in vitro Pro-Arrhythmia (CiPA) panel for early arrhythmogenic risk assessment in drug discovery and development. We used automated patch-clamp of human ion channels heterologously expressed in mammalian cell lines to evaluate half-maximal inhibitory concentrations (IC50). Naringenin blocked all CiPA currents tested with IC50 values in the 30 µM – 100 µM concentration-range. The rank-order of channel sensitivity was the following: hERG > Kir2.1 > NaV1.5 late > NaV1.5 peak > KV7.1 > KV4.3 > CaV1.2. This multichannel inhibitory profile of naringenin suggests exercising caution when large amounts of grapefruit juice or other citrus juices enriched in this flavanone are drunk in conjunction with QT prolonging drugs or by carriers of congenital long QT syndromes.

FALSIFICATION OF CITRUS JUICES

The problem of falsification of juice products today is urgent due to the fact that this group of food products is consumed by all segments of the population. Today, at the same time as the presence of a wide range of juices in the modern market, it is quite difficult to identify them and prevent falsification. As a result, there is a need to strengthen control over the quality of juice products and to develop criteria for the authenticity of juices. The article presents the results of the study of the quality of orange juices purchased in the retail outlets in Minsk. In order to identify and detect falsification, a comprehensive assessment of juices was carried out. The author determined the main indicators of the quality and safety of juices such as dissolved solids, titratable acidity, pH level, sugar-acid ratio. However, due to the fact that these indicators can be easily adjusted by adding organic acids, sugars and other components, a study was carried out of such indicators as the content of oxymethylfurfural and formol index, which are the most difficult to falsify. Standard and common methods were used during the experiment. The quality assessment also included an analysis of the causes of deviations that could be found during the study. These causes may be explainable properties of raw materials or technological features of production.

Antibacterial activity of crude extract of Tabernaemontana catharinensis latex (A. DC) against Alicyclobacillus spp.

Alicyclobacillus spp. is composed of Gram-positive, aerobic, thermoacidophilic, endospore-forming bacteria that cause food and beverage spoilage. The presence of Alicyclobacillus spp. may result in the production of guaiacol, which leads to sensory changes in the odour and taste of citrus juices and acidic foods. Tabernaemontana catharinensis (A. DC) is a plant belonging to the family Apocynaceae that produces milky latex with several biological activities described as antioxidant, antiviral, antimicrobial, trypanocidal and anti-leishmanicidal. Therefore, this study aims to evaluate the antimicrobial activity of the crude latex of T. catharinensis (A. DC) against microorganisms of the genus Alicyclobacillus spp. The minimum inhibitory concentration of latex was 7.81 μg/ml for the five Alicyclobacillus species analysed. The minimum bactericidal concentration for the species Alicyclobacillus acidoterrestris 0244T, A. hesperidum 0298T, A. acidiphilus 0247T and A. cycloheptanicus 0297T was 250 μg/ml. Cytotoxicity analysis demonstrated that latex was toxic to Vero cells at concentrations greater than 84.67 μg/ml. Scanning electron microscopy revealed changes in the cell wall of A. acidoterrestris 0244T present in orange juice when treated with crude latex. The results obtained suggest that the crude latex of T. catharinensis (A. DC) displays an antimicrobial effect against Alicyclobacillus, with potential for application in the food industry.

Concise enantioselective synthesis of wine lactone via intramolecular Diels–Alder reaction

An enantioselective synthesis of (3S,3aS,7aR)-wine lactone, a major aroma component of white wine and citrus juices, was achieved starting from (S)-2-methyl-3-butenoic acid. An intramolecular Diels–Alder reaction was employed as a key step.

Biochemical Characteristics and Antioxidant Properties of Citrus Juice from Lemon (Citrus limon), Lime (Citrus aurantifolia) and Grapefruit (Citrus paradisi) as Influenced by Degree of Ripening

The influence of degree of ripening (unripe, half-ripe and ripe) of citrus fruits (lemon, lime and grapefruit) on the biochemical characteristics and antioxidant potential of their juices was investigated. The juice yield from the citrus fruits was affected by the level of ripening as the highest juice yield was obtained when the fruits were at ripe stage giving 25.2 mL/100 g (lemon), 43.3 mL/100 g (lime), and 21.1 mL/100 g (grapefruit). The biochemical characteristics of the citrus juices revealed that the pH values were generally increasing with an increasing level of ripening particularly for lime and grapefruit while the pH of lemon juice was decreasing with an increase in the degree of ripening. The lowest pH values exhibited by the citrus fruits were 2.87 (ripe lemon), 2.16 (unripe lime), and 3.27 (unripe grapefruits). The total acidity of the citrus juices essentially exhibited an inverse relationship with their corresponding pH values. The highest ascorbic acid contents of the juices were 51.3 g/100mL (unripe lemon), 38.9 g/100mL (unripe lime), and 44.7 g/100mL (unripe grapefruit) while the highest total phenolic contents were 722 µg GAE/mL (unripe lemon), 207 µg GAE/mL (unripe lime), and 646 µg GAE/mL (unripe grapefruit); indicating a significant impact of degree of ripening on the parameters. The antioxidant activity of the citrus juices using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical assay revealed a significant influence of degree of ripening and juice volume on the activity. The percent inhibition of DPPH free radical by the juices was generally higher at an unripe stage of fruit maturity as well at greater juice volume. The ferric-reducing antioxidant potential (FRAP) of the citrus juices was also influenced by the level of ripening of the fruit. The FRAP values were generally higher at unripe stage which were 3.72 µ mol Fe(II)/g (unripe lemon), 4.98 µ mol Fe(II)/g (unripe lime) and 9.53 µmolFe(II)/g (unripe grapefruit).

Chemical route for synthesis of citric acid from orange and grape juices

Citrus fruits contain sufficient citric acid which is a main tricarboxylic acid. The properties of citric acid make it an important additive in various process industries. The aim of this experimental study is to produce citric acid from orange and grape juices. The chemical route for synthesis of citric acid from citrus juices involves three steps: (i) Neutralization to adjust pH (9-11) with 2.8 M NaOH solution, (ii) Addition of CaCl2 solution (40.3-41.1% (w/v)), and (iii) Acidification with H2SO4 solution (1.5-2.3 M) to produce citric acid. In this study, the fruits were peeled, crushed, filtered, neutralized, added CaCl2 solution and acidified to obtain citric acid. The experiments were carried out by varying final pH of solution, concentrations of CaCl2 and H2SO4 solutions maintaining volume constant. A maximum yield of citric acid at 91.1 and 79.8% from orange and grape fruits at optimum final pH of solution, concentrations of CaCl2 and H2SO4 solutions at 10, 40.7% (w/v) and 1.9 M respectively were achieved. Finally, the purified citric acid crystals were characterized using FTIR and XRD. Thus, it could be concluded that orange fruit would be a promising source for the production of citric acid than grape.