The toxicology of nitrates and nitrites with particular reference to the potability of water supplies. A review

Coupling of digital image processing and three-way calibration to assist a paper-based sensor for determination of nitrite in food samples

In this work, a novel and very interesting analytical methodology based on coupling of digital image processing and three-way calibration has been developed for determination of nitrite in food samples.

Novel Method of Preparation and Activity Research on Arctigenin from Fructus Arctii

Background:

Arctigenin has many pharmacological activities with clinical significance and is derived from Arctium lappa L. However, the present extraction method is inefficient and does not have meaningful industrial production.

Objective:

A new method to directly prepare arctigenin was established by combining enzyme-assisted extraction and central composite design. Arctigenin's further pharmacological activity was also surveyed in vitro.

Materials and Methods:

β-D-Glucosidase, a food-grade enzyme, was added directly to the fruits of A. lappa L. to hydrolyze the arctiin to arctigenin, and the obtained samples were subsequently subjected to ethanol (30%, v/v) extraction. The pharmacological activity of the extraction and arctigenin was determined by inhibiting acetylcholinesterase (AChE) and scavenging nitrite.

Results:

The factors investigated include the enzyme concentration (0.5%–2.5%), ultrasound time (10 min⁻³ 0 min), and extraction temperature (30°C–50°C). From the analysis of the results by Design-Expert (V8.0.6), the optimal extraction conditions were obtained: enzyme concentration (1.4%), ultrasound time (25 min), and extraction temperature (45°C). The highest yield of arctigenin, obtained under the optimal conditions was 6.39%, representing an increase of 28.15% compared to the reference extraction without enzyme processing. The IC₅₀ values of the extraction and arctigenin, respectively, for inhibiting AChE were 0.572 mg/ml and 0.462 mg/ml, and those for nitrite-scavenging were 34.571 mg/ml and 17.49 mg/ml.

Conclusions:

The results demonstrate that using an enzyme directly in the production is an effective means for extracting arctigenin from Fructus arctii. The extraction has the activities of inhibiting AChE and scavenging nitrite, probably because there has arctigenin in it. It is implied that the extraction and arctigenin could contribute to human health in clinical applications.

SUMMARY

The new method of adding enzyme directly to the preparation of arctigenin was carried out instead of preparing arctigenin by two-step method

Three factors affecting the efficiency of preparation were analyzed and discussed include the enzyme concentration, ultrasound time, and extraction temperature by central composite design

This new method of preparing arctigenin improved the yield significantly than other methods

Arctigenin has remarkable pharmacological activities of inhibiting acetylcholinesterase and scavenging nitrite.

Abbreviations used: AChE: Acetylcholinesterase, CCD: Central composite design, TCM: Traditional Chinese medicines, AD:

Experimental study of the anti-tumour activity and pharmacokinetics of arctigenin and its valine ester derivative

Arctigenin (ARG) is a functional active component that has important physiological and pharmacological activities. The anti-tumour and anti-inflammatory activities of ARG show good potential for application and development, but this material has the defect of low water solubility. In this experiment, the valine derivative of ARG (ARG-V) was designed and synthesized to overcome this disadvantage. The ARG amino acid, EDCI and DMAP were raw materials in the addition reaction, with a molar ratio of 1:2:2:0.5. The yield of ARG-V was up to 80%. ARG-V has strong anti-tumour activity in vivo and in vitro. The inhibitory rate of ARG-V was 69.2%, with less damage to the immune organs and different degrees of increased serum cytotoxicity. Moreover, the pharmacokinetics of ARG following oral administration and ARG-V following oral administration in rats were also studied. The C_max and AUC values of ARG-V showed significant differences compared to ARG. The relative bioavailabilities of three doses of ARG-V compared to ARG were 664.7%, 741.5% and 812.9%. These pharmacokinetic results may be useful for further studies of the bioactive mechanism of ARG and provide a theoretical basic for clinical use.

Spectrofluorimetric determination of trace nitrite with a novel fluorescent probe

A simple, sensitive and selective fluorimetric determination for trace nitrites was developed using an unsymmetrical rhodamine with a high fluorescence quantum yield and large Stokes shift. The method is based on the reaction of the unsymmetrical rhodamine with nitrite in an acidic medium to form a nitroso product, which has much lower fluorescence because the electron-withdrawing effect of the nitroso group influences the system of p-pi conjugation between N atom and benzene ring. Under optimum conditions, the fluorescence quenching intensity is linear over a nitrite concentration range of 1.0 x 10(-8) to 3.5 x 10(-7)M. The detection limit is 2.0 x 10(-10)M (S/N=3). The method was applied to the determination of nitrite in tap water and lake water with satisfactory results. The mechanism for the reaction is also reported.

Sensing nitrite through a pseudoazurin-nitrite reductase electron transfer relay

Nitrite is converted to nitric oxide by haem or copper-containing enzymes in denitrifying bacteria during the process of denitrification. In designing an efficient biosensor, this enzymic turnover must be quantitatively assessed. The enzyme nitrite reductase from Alcaligenes faecalis contains a redox-active blue copper centre and a nonblue enzyme-active copper centre. It can be covalently tethered to modified gold-electrode surfaces in configurations in which direct electron transfer is possible. A surface cysteine mutant of the enzyme can be similarly immobilised on bare electroactive gold substrates. Under such circumstances, however, electron transfer cannot be effectively coupled with substrate catalytic turnover. In using either the natural redox partner, pseudoazurin, or ruthenium hexammine as an "electron-shuttle" or "conduit" between enzyme and a peptide-modified electrode surface, the coupling of electron transfer to catalysis can be utilised in the development of an amperometric nitrite sensor.