Different concentrations (1.95–1,000 μg/mL) of methanolic extracts of tested samples (2.5 mL) were added to 0.3 mM ethanolic solution (1 mL) of DPPH. The values of absorbance (Ab) were recorded at 517 nm on a Unicam UV/Vis spectrophotometer after 30 min at 25°C in dark. A blank was created using ethanol (1 mL) and plant extract solution (2.5 mL), and a control of DPPH solution and methanol (Qanash et al., 2023a (link)). The following equation was utilized to estimate the % of antioxidant activity:
Uv vis spectrophotometer
Manufactured by Unico
Sourced in United Kingdom, China, United States
The UV-vis spectrophotometer is a laboratory instrument used to measure the absorption of ultraviolet and visible light by a sample. It can determine the concentration of a substance in a solution by measuring the amount of light absorbed at a specific wavelength.
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Lab products found in correlation
Sv 1422, by Memmert (1 mentions)
Lactobacilli mrs, by BD (1 mentions)
Tryptic soy, by BD (1 mentions)
Nutrient broth, by BD (1 mentions)
Lambda 25, by PerkinElmer (1 mentions)
Usp dissolution apparatus, by Pharma Test (1 mentions)
Bi 200sm, by Brookhaven Instruments (1 mentions)
Wb 2000, by Heidolph (1 mentions)
28 protocols using uv vis spectrophotometer
1
DPPH Radical Scavenging Assay for Antioxidant Activity
2
Thermal Stability of Encapsulated Bromelain
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The thermal stability test was conducted by following the method described by Naghdi et al. (2019) (link), with some modifications. Free bromelain (2 mg; 0.6 Unit/mL) and 100 mg of encapsulated bromelain in dried hydrogel beads were added to separate tubes containing 2 ml of phosphate buffer saline (PBS) (at constant pH 7.4) and incubated in a water bath (SV 1422, Memmert GmbH + Co. KG, Germany) at 30, 65, 72, and 95°C for 1, 2, 3, 4, and 5 min. Following the incubation period, aliquots were taken at various time intervals, and the samples were cooled to 25°C. The bromelain activity of free and encapsulated samples was measured spectrophotometrically (UNICAM, UV/Vis Spectrophotometer, United Kingdom) at 660 nm based on the method explained in bromelain activity determination. Subsequently, the residual protease activity was measured, and the relative proteolytic activity (%) was further calculated through Eq. 3 :
3
Measuring Ammonia Volatilization using Ventilation Method
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Ammonia volatilization was measured every 10 days after DMPP application. Twelve ammonia volatilization measurement points were evenly distributed in each tree disk. The average of 12 results was used as one replicate. Ammonia volatilization was measured using the ventilation method (Li et al., 2020a (link)). A PVC collection tube (0.20 m diameter, 0.25 m height) was inserted into the soil at a depth of 0.05 m with a phosphoglycerol-soaked sponge placed inside as an absorbent, which was collected (and replaced) daily (10:00 am) throughout the experiment period. The phosphoglycerol-soaked sponges bearing the collected samples were transported to the laboratory and immediately immersed in 500 mL 1.0 mol L–1 KCl solution in 1 L polyethylene bottles. Bottles were sealed and shaken at 200 rpm for 1 h on a reciprocating shaker. The NH4+-N concentrations of the extracted solutions from each bottle were measured by colorimetry (λ = 630 nm) using a UV-VIS spectrophotometer (Unico, Shanghai, China). The NH3 volatilization rates were calculated as follows: RAV = M/(A × D) × 10–2, where RAV is the NH3 volatilization rate (kg N ha–1 d–1), M is the amount of NH3-N collected in the sponge (mg), which is equal to the NH4+-N contents of the extracted solutions, A is the cross-sectional area of the sponge (m2), and D is the interval of sample collection (d).
4
Reducing Power Capacity of A. nilotica
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The reducing power capacity of A. nilotica was estimated by the method as described by Nabavi et al. [12 ], with slight modifications. Increasing concentrations (125 to 1000 μg/ml) of each extract were prepared from a stock solution. The plant extract (2.5 ml) was mixed with phosphate buffer solution (PBS; 0.2 M, pH 6.6, 2.5 ml) and potassium ferricyanide (2.5 ml, 1% w/v), and incubated at 50 °C for 20 min. The reaction was stopped by adding trichloro acetic acid (TCA; 2.5 mL, 10% w/v) to the reaction mixture. The reaction mixture was centrifuged at 940×g for 10 min and the supernatant (2.5 ml) was mixed with ultra-purified water (2.5 ml) and ferric chloride (0.5 ml, 0.1%, w/v) solution. The absorbance was then measured at 700 nm by UV- visible spectrophotometer (UNICAM UV/Vis Spectrophotometer, UK), using ascorbic acid as positive control.
5
Buccal Dissolution of Powdered Drugs
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Using a modified paddle method from the European Pharmacopeia [24 ], the rate of drug release of the powders was examined (Hanson SR8 Plus, Teledyne Hanson Research, Chatsworth, CA, USA). The Pharmacopoeia does not contain any specification for orally dispersible systems, so the release medium to mimic saliva was prepared based on the literature [25 (link)]. The analysis was carried out under buccal circumstances (37 °C and pH 6.8). The following components were included in 50 mL of artificial saliva: 8.00 g/L NaCl, 2.38 g/L NaH2PO4, and 0.19 g/L KH2PO4. The paddle rotated at 50 rotations per minute. The sample preparation was completed after 5, 10, 15, and 30 min. To maintain the constant permanent volume, saliva was simultaneously added at each sampling point to replace 2 mL of the sample. For filtering, cellulose ester membranes with 0.45 μm pore sizes were employed. Following filtration, spectrophotometry at 355 nm (Unicam UV/VIS Spectrophotometer, Cambridge, UK) was used to determine the drug content of the aliquots. The experiments were carried out in three sets. The investigation was performed in the case of the raw PRX and the OL containing nanosized PRX, to compare their drug release.
6
Adsorption Optimization for Contaminant Removal
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The adsorption experiments were conducted to determine the contact time (0–24 h), adsorbent dosage (0.2–1.0 g/L), temperature (25–45 °C), initial concentration (5–500 mg/L) and initial solution pH (2–10) effects on contaminants removal. All the experiments were conducted in the 100 mL Erlenmeyer flasks with 20 mL of contaminants solutions. The mixed solutions were shaken at 25 °C for a fixed time. After magnetic separation, the remaining solution was filtered using 0.45 μm millipore membrane filters. The concentration of residual TC and CR were measured by a UV–vis spectrophotometer (Unico, Shanghai, China) at wavelengths of 357 and 269.5 nm, respectively. The adsorption capacity (qt, mg/g) at time t was calculated as follows:
where C0 (mg/L) is the initial dye concentration; Ct (mg/L) is the final dye concentration at time t; m (mg) is the adsorbent mass and V (mL) is solution volume.
where C0 (mg/L) is the initial dye concentration; Ct (mg/L) is the final dye concentration at time t; m (mg) is the adsorbent mass and V (mL) is solution volume.
7
Disinfection and Biofilm Formation Assay
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The Salmonella enteritidis S01 strain was isolated from vegetable salads, and kindly provided by Professor S. H. Cui from the National Institutes for Food and Drug Control of China. Bacterial isolates from the FVs processing plant and S. enteritidis S01 were applied to the disinfection challenges and mixed-species biofilms formation. Inoculum was prepared as following: one loop of pure bacteria colony was transferred into LB broth and incubated at 37 °C overnight. Cultures were centrifuged at 2500 × g for 10 min, and the pellets were diluted with 1/2 dilution of LB broth at the optical density (OD) of 600 nm to 0.5 using a UV-vis spectrophotometer (UNICO, USA). The bacterial inoculum contained approximately ∼107 CFU mL−1 populations of each strain.
8
Diffusion Test of Cellulose Ester Membrane
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The Side-Bi-Side™ (Crown Glass, USA) diffusion test was carried out in nasal conditions. The cellulose ester membrane with 0.45 µm pore diameter was soaked in isopropyl myristate, and the donor phase was tempered to 30°C at pH 5.6. The acceptor phase was pH 7.4, and the content of the diffused drug was measured spectrophotometrically at 362 nm (Unicam UV/Vis Spectrophotometer).
9
Bacterial Growth Kinetics in Leaf Infusions
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Scaffolds were removed from the pressure vessel, aseptically opened in a sterile tissue culture hood and washed with DI water for 24 h. Leaves were cut in half and placed in Erlenmeyer flasks. Each flask was filled with 25 mL of one of four different bacterial broths, Tryptic Soy (BD), Nutrient Broth (BD), Brain Heart Broth (Sigma) or Lactobacilli MRS (BD). Turbidity was measured after 72 h incubation under shaking at 35 °C by a UV/VIS Spectrophotometer (Unico, USA) at 600 nm wavelength.
10
Solubility Characterization of APIs and Nanocrystals
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The solubility of the raw APIs and dry nanocrystals was measured in phosphate-buffered solution (PBS) at a pH of 5.6 and 7.4. Excess amounts of the samples were added into 5 mL of the required PBS and stirred for 24 h at 25 °C. Then, the suspensions were filtered through 450 nm, and the concentrations were determined spectrophotometrically by UV (Unicam UV/VIS Spectrophotometer, Cambridge, UK) at λmax of 363 nm.
The calibration curve of MLX was performed between 1 and 15 µg mL–1. The calibration curve was linear throughout the whole range tested and described by the equation A = 0.0484 Conc.+ 0.0014 (R2 = 0.999) at PBS of pH 7.4 and A = 0.0251 Conc.* 0.0014 (R2 = 0.9997) at PBS of pH 5.6.
The calibration curve of MLX was performed between 1 and 15 µg mL–1. The calibration curve was linear throughout the whole range tested and described by the equation A = 0.0484 Conc.+ 0.0014 (R2 = 0.999) at PBS of pH 7.4 and A = 0.0251 Conc.* 0.0014 (R2 = 0.9997) at PBS of pH 5.6.
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