Zhimu-Huangbai codecoction for the treatment of type II diabetes mellitus through its self-assembling nanoparticles

Traditional Chinese medicine (TCM) decoctions represent a complex system comprising multiple phases, and their therapeutic effects cannot be fully elucidated solely at the molecular level. The nanophase within TCM decoctions plays a significant role in mediating their pharmacological activities. Zhimu and Huangbai herbal decoction (ZBD), traditionally used to treat type 2 diabetes mellitus (T2DM), is a formulation combining Rhizoma Anemarrhenae and Cortex phellodendri chinensis. Our prior research identified natural nanoparticles (N-ZBD) within ZBD. However, the role of these nanoparticles in ZBD's anti-T2DM effects and their potential impact on the oral bioavailability of its active components remain unclear. Therefore, this study aimed to examine the anti-T2DM effects of N-ZBD and to assess whether N-ZBD could enhance the bioavailability of its primary active compounds. Initially, we employed a dialysis centrifugation method to isolate the N-ZBD (nanoparticles derived from Zhimu-Baihu Decoction) from ZBD. The separated N-ZBD exhibited an average particle size of 234.4 ± 1.04 nm, a polydispersity index (PDI) of 0.56 ± 0.06, and a zeta potential of - 12 .97 ± 1.46 mV. Then, a type 2 diabetes mellitus (T2DM) rat model was created by administering a low dose of streptozotocin (35 mg/kg) intraperitoneally following 4 weeks on a high-fat diet. After a 7-week treatment period, compared with the model group, the levels of FBG, TC, TG and LDL in MET group, N-ZBD group and ZBD group were significantly reduced, and the morphology of islets was significantly improved. In all phases state of ZBD, N-ZBD had a significant therapeutic effect on T2DM rats, which was comparable to that of ZBD. In order to explore whether N-ZBD has the effect of promoting absorption, we assessed the intestinal absorption properties of N-ZBD, ZBD, and free drugs (mangiferin, timosaponin BII, berberine, phellodendrine, neomangiferin and jatrorrhizine) utilizing a single-pass intestinal perfusion (SPIP) model. Compared to free drugs, N-ZBD enhanced the absorption of active ingredients in the jejunum and ileum. In order to explore whether N-ZBD can improve the bioavailability of active ingredients, a method using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was also established to compare the pharmacokinetic profiles of six primary active compounds in plasma after the oral administration of ZBD, N-ZBD and free drugs. The pharmacokinetic profiles of N-ZBD and ZBD in rats were comparable. Notably, N-ZBD exhibited higher C_max, AUC_0-t, and T_1/2 values for the index compounds compared to free drugs and a reduced plasma clearance rate. In conclusion, N-ZBD is primarily responsible for ZBD's anti-T2DM effects and significantly enhances the bioavailability of active ingredients, highlighting the essential role of natural nanoparticles in the therapeutic effectiveness of decoctions.