A Study of Synergy of Combination of Eosin B with Chloroquine, Artemisinin, and Sulphadoxine-Pyrimethamine on Plasmodium falciparum In Vitro and Plasmodium berghei In Vivo

In vitro and in vivo antiplasmodial activity of a synthetic dihydroartemisinin-eosin B hybrid

With the inexorable prevalence and spread of drug-resistant malaria strains, many efforts have been made to find alternative chemotherapeutic agents. In this regard, scientists have developed the concept of hybridization of two or more active pharmacophores into a single chemical compound, resulting in "antimalarial hybrids." The aim of this study was planned based on the highly synergistic effect of the physical hybrid of dihydroartemisinin (DHA) with eosin B (EB). Therefore, a chemical hybrid of the two compounds (DHA-EB) was synthesized, and its antimalarial activity was investigated in vitro and in vivo. The drug hybrid was fabricated through a propionyl ester linker between DHA and EB. The antiplasmodial activity of the new hybrid was tested in vitro on the blood stages of Plasmodium falciparum (chloroquine-sensitive, 3D7 strain) and also evaluated in vivo by Peters' standard test in mice infected with Plasmodium berghei. The hybrid compound was also assessed for in vivo toxicity. Among all the compounds studied, a DHA-EB hybrid showed an appropriate inhibition percentage (53%) was at a very low dose (0.65 nM). The highest in vivo antimalarial activity until the 9th day was related to DHA-EB in a low dose (0.5 mg/kg). Also, the most survival rate was observed in the test group of hybrid compound at a dose of 1.5 mg/kg for 22 days. No external changes were identified in the toxicity assay. The weight of internal organs of treated animals and that of controls indicated nontoxicity of DHA-EB even after 60 days of consumption. In vitro and in vivo studies substantiated that DHA-EB hybrid has the potential for developing as a safe antimalarial drug.

Uncovering the anti-obesity constituents in Ginkgo biloba extract and deciphering their synergistic effects

Obesity has been recognized as a key risk factor for multiple metabolic disorders, including diabetes, cardiovascular diseases and many types of cancer. Herbal medicines have been frequently used for preventing and treating obesity in many countries, but in most cases, the key anti-obesity constituents in herbs and their anti-obesity mechanisms are poorly understood. This study demonstrated a case study for uncovering the anti-obesity constituents in an anti-obesity herbal medicine (Ginkgo biloba extract) and deciphering their synergistic effects via targeting human pancreatic lipase (hPL). Following screening the anti-hPL effects of eighty herbal medicines, Ginkgo biloba extract (GBE50) was found with the most potent anti-hPL activity. Global chemical profiling of herbal constituents coupling with hPL inhibition assay revealed that the bioflavonoids and several flavonoids in GBE50 were key anti-hPL constituents. Among all tested thirty-eight constituents, sciadopitysin, bilobetin, quercetin, isoginkgetin, and ginkgetin showed potent anti-hPL effects (IC50 values <2.5 μM). Inhibition kinetic analyses suggested that sciadopitysin, bilobetin, quercetin, isoginkgetin, and ginkgetin acted as non-competitive inhibitors of hPL, with the Ki values were <2 μM. Docking simulations revealed that four bioflavonoids (sciadopitysin, bilobetin, isoginkgetin, and ginkgetin) could tightly bind on hPL at cavity 2, which it is different from the binding cavity of quercetin on hPL. Further investigations demonstrated that the combinations of quercetin and one bioflavonoid-type hPL inhibitor (sciadopitysin or bilobetin) showed synergistic anti-hPL effects, suggesting that the multi-components in GBE50 may generate more potent anti-hPL effect. Collectively, our findings uncovered the anti-obesity constituents in GBE50, and explored their anti-hPL mechanisms as well as synergistic effects at molecular levels, which will be very helpful for further understanding the anti-obesity mechanisms of Ginkgo biloba.

Herb-drug interaction between Styrax and warfarin: Molecular basis and mechanism

BACKGROUND

Styrax, one of the most famous folk medicines, has been frequently used for the treatment of cardiovascular diseases and skin problems in Asia and Africa. It is unclear whether Styrax or Styrax-related herbal medicines may trigger clinically relevant herb-drug interactions.

PURPOSE

This study was carried out to investigate the inhibitory effects of Styrax on human cytochrome P450 enzymes (CYPs) and to clarify whether this herb may modulate the pharmacokinetic behavior of the CYP-substrate drug warfarin when co-administered.

STUDY DESIGN

The inhibitory effects of Styrax on CYPs were assayed in human liver microsomes (HLM), while the pharmacokinetic interactions between Styrax and warfarin were investigated in rats. The bioactive constituents in Styrax with strong CYP3A inhibitory activity were identified and their inhibitory mechanisms were carefully investigated.

METHODS

The inhibitory effects of Styrax on human CYPs were assayed in vitro, while the pharmacokinetic interactions between Styrax and warfarin were studied in rats. Fingerprinting analysis of Styrax coupled with LC-TOF-MS/MS profiling and CYP inhibition assays were used to identify the constituents with strong CYP3A inhibitory activity. The inhibitory mechanism of oleanonic acid (the most potent CYP3A inhibitor occurring in Styrax) against CYP3A4 was investigated by a panel of inhibition kinetics analyses and in silico analysis.

RESULTS

In vitro assays demonstrated that Styrax extract strongly inhibited human CYP3A and moderately inhibited six other tested human CYPs, as well as potently inhibited warfarin 10-hydroxylation in liver microsomes from both humans and rats. In vivo assays demonstrated that compared with warfarin given individually in rats, Styrax (100 mg/kg) significantly prolonged the plasma half-life of warfarin by 2.3-fold and increased the AUC_(0-inf) of warfarin by 2.7-fold when this herb was co-administrated with warfarin (2 mg/kg) in rats. Two LC fractions were found with strong CYP3A inhibitory activity and the major constituents in these fractions were characterized by LC-TOF-MS/MS. Five pentacyclic triterpenoid acids (including epibetulinic acid, betulinic acid, betulonic acid, oleanonic acid and maslinic acid) present in Styrax were potent CYP3A inhibitors, and oleanonic acid was a competitive inhibitor against CYP3A-mediated testosterone 6β-hydroxylation.

CONCLUSION

Styrax and the pentacyclic triterpenoid acids occurring in this herb strongly modulate the pharmacokinetic behavior of warfarin via inhibition of CYP3A.