Naoxintong capsule (NXTC) was a famous patent medicine of Traditional Chinese Medicine (TCM) to treat cerebrovascular diseases in China. An LC‐MS/MS method was developed for simultaneous determination of 11 major ingredients (paeoniflorin, ecdysterone, amygdalin, mulberroside A, caffeic acid, ferulic acid, salvianolic acid B, astragaloside IV, formononetin, cryptotanshinone, and tanshinone IIA) in NXTC in rat plasma. All analytes were separated on an Eclipse plus C₁₈ column using a gradient mobile phase system of acetonitrile‐0.1% formic acid aqueous solution. The lower limits of quantification of 11 ingredients were between 0.075 and 10 ng mL⁻¹. The precision was less than 15% and the accuracies were between 85% and 115%. The results showed that caffeic acid, ferulic acid, formononetin, cryptotanshinone, and tanshinone IIA could be detected after oral administration of NXTC. The validated method was successfully applied to pharmacokinetic study of the caffeic acid, ferulic acid, formononetin, cryptotanshinone, and tanshinone IIA in rats after oral administration of NXTC at single and triple dose.

A sensitive and effective method was developed for clarifying the pharmacokinetic properties of six compounds (including hyperin, chlorogenic acid, neochlorogenic acid, p-coumaric acid, astragalin, and isoquercitrin) in two processed Cuscutae Semen samples by high performance liquid chromatography mass spectrometry (HPLC-MS/MS). The six compounds were separated by acetonitrile and 0.1% formic acid-water on an Agilent Eclipse plus C18 column (4.6 mm × 100 mm, 1.8 μm). All compounds were analyzed with negative ion mode in multiple reaction monitoring (MRM). The lower limits of quantification (LLOQ) of hyperin, astragalin, neochlorogenic acid, chlorogenic acid, isoquercitrin, and p-coumaric acid were 1, 0.1, 4, 0.1, 2, and 4 ng·mL⁻¹, respectively. The validated approach was effectively used for the pharmacokinetics of six compounds of two processed Cuscutae Semen samples after oral administration to rat. The results indicated that salt processing could improve the adsorption and bioavailability of astragalin in Cuscutae Semen.

Coproheme decarboxylase (ChdC) is an important enzyme in the coproporphyrin-dependent pathway (CPD) of Gram-positive bacteria that decarboxylates coproheme on two propionates at position 2 and position 4 sequentially to generate heme b by using H₂O₂ as an oxidant. This work focused on the ChdC from Geobacillus stearothermophilus (GsChdC) to elucidate the mechanism of its sequential two-step decarboxylation of coproheme. The models of GsChdC in a complex with substrate and reaction intermediate were built to investigate the reorienting mechanism of harderoheme. Targeted molecular dynamics simulations on these models validated that harderoheme is able to rotate in the active site of GsChdC with a 19.06-kcal·mol⁻¹ energy barrier after the first step of decarboxylation to bring the propionate at position 4 in proximity of Tyr145 to continue the second decarboxylation step. The harderoheme rotation mechanism is confirmed to be much easier than the release–rebinding mechanism. In the active site of GsChdC, Trp157 and Trp198 comprise a “gate” construction to regulate the clockwise rotation of the harderoheme. Lys149 plays a critical role in the rotation mechanism, which not only keeps the Trp157–Trp198 “gate” from being closed but also guides the propionate at position 4 through the gap between Trp157 and Trp198 through a salt bridge interaction.