For the highly chemoselective separations of lactate (LA) and 3-hydroxybutyrate (3HB) enantiomers in mammalian urine, an online three-dimensional HPLC system (3D-HPLC) composed of reversed-phase (KSAARP, 1.0 mm i.d. x 250 mm), mixed-mode (KSAAMX, 1.5 mm i.d. x 250 mm) and enantioselective (Chiralpak AD-H, 2.0 mm i.d. x 250 mm) columns has been developed. Following the pre-column derivatization with 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ), NBD-LA and 3HB were separated in the first and second dimensions as their scalmic D plus L mixtures and the enantiomer separations were performed in the third dimension with high separation factors (α = 1.70 for LA; α = 1.43 for 3HB). The present system was applied to the urine of mice and humans. For the mice urine, the D and L-forms of NBD-LA and 3HB were well separated without visible interfering compounds, and trace levels of D-LA (less than 5% of total LA) and non-negligible amounts of L-3HB (34.4% of the total 3HB) were clearly observed. Trace levels of the LA and 3HB enantiomers were detected for the human urine samples, although the existence of a few interfering peaks were observed.

<abstract> <p>Optical activity and its relation to molecular chirality are significant in the measurement of optical rotation or circular dichroism characteristics to determine the absolute configuration of a chiral molecule. A quarter-wave plate, which is usually made from quartz, can convert linearly polarized light into circularly polarized light. In this study, we suggest using <sc>l</sc>-lactic acid (<sc>l</sc>-LA), a chiral material, and a water-based transparent glue to produce biodegradable films. Adjusting the number of thin layers, which are deposited from the mixture of <sc>l</sc>-LA and polyvinyl alcohol, leads to different phase differences, forming <sc>l</sc>-LA films. A modified microscope system was used to observe the appearance of the <sc>l</sc>-LA wave plates. Six layers and 0.8% <sc>l</sc>-LA solution were the optimal conditions to fabricate an <sc>l</sc>-LA film. The circular polarization experiment showed that the changes in maximum and minimum light intensity were within 2% compared to the average light intensity at a specific angle of the <sc>l</sc>-LA film. The performance of the <sc>l</sc>-LA film was consistent with that of a commercial quarter-wave plate. In conclusion, circularly polarized light was successfully produced using the <sc>l</sc>-LA film. The biodegradable <sc>l</sc>-LA film has widespread application in the field of biomedicine. Featured Application: <sc>l</sc>-Lactic acid film uses biodegradable and biocompatible materials. It can produce circularly polarized light and is beneficial for application in biomedicine.</p> </abstract>

In this study, we developed a simple fluorescence sensing system to rapidly measure the total carbonyl stress in urine because carbonyls may form advanced glycation end products, leading to diseases. The traditional method for detecting carbonyl stress has been high-performance liquid chromatography (HPLC), which detects glyoxal, methylglyoxal, and 3-deoxyglucosone contents. The excitation and emission wavelengths used in the sensing system to monitor aldehyde content in urine were 340 and 500 nm, respectively. Rat urine samples were derivatized with 5,6-diamino-2,4-hydroxypyrimidine sulfate dihydrate. A 20 µL sample was added to a carrier composed of polydimethylsiloxane for testing, and only 1 s was required for detection. According to the fluorescence intensity results, the calibration curve for the total content of all aldehydes in the urine had a good degree of linearity with the fluorescence intensity (R 2 = 0.9879). In addition, the urine of diabetic and healthy rats was tested, and the correlation coefficient between the total carbonyl content detected by the simple fluorescence system and HPLC reached 0.8132. Collectively, our findings demonstrated that our system can rapidly measure total carbonyl stress in urine with a small sample volume.

Background: Most Aristolochiaceae plants are prohibited due to aristolochic acid nephropathy (AAN), except Xixin ( Asarum spp. ). Xixin contains trace amounts of aristolochic acid (AA) and is widely used in Traditional Chinese Medicine. Methylglyoxal and D-lactate are regarded as biomarkers for nephrotoxicity. Thus, this study aimed to evaluate tubulointerstitial injury and interstitial renal fibrosis by determining urinary methylglyoxal and D-lactate after withdrawal of low-dose AA in a chronic mouse model. Methods: C3H/He mice in the AA group ( n =24/group) were given ad libitum access to distilled water containing 3 µg/mL AA (0.5 mg/kg/day) for 56 days and drinking water from days 57 to 84. The severity of tubulointerstitial injury and fibrosis were evaluated using the tubulointerstitial histological score (TIHS) and Masson’s trichrome staining. Urinary and serum methylglyoxal were determined by high-performance liquid chromatography (HPLC); urinary D-lactate were determined by column-switching HPLC. Results: After AA withdrawal, serum methylglyoxal in the AA group increased from day 56 (429.4±48.3 μg/L) to 84 (600.2±99.9 μg/L), and peaked on day 70 (878.3±171.8 μg/L; p <0.05); TIHS and fibrosis exhibited similar patterns. Urinary methylglyoxal was high on day 56 (3.522±1.061 μg), declined by day 70 (1.583±0.437 μg) and increased by day 84 (2.390±0.130 μg). Moreover, urinary D-lactate was elevated on day 56 (82.10±18.80 μg) and higher from day 70 (201.10±90.82 μg) to 84 (193.28±61.32 μg). Conclusions: Methylglyoxal is induced after AA-induced tubulointerstitial injury, thus methylglyoxal excretion and metabolism may be a detoxification and repair strategy. A low cumulative AA dose is the key factor that limits tubulointerstitial injury and repair. Thus, AA-containing herbs, especially Xixin, should be used at low doses for short durations (less than one month).