Analytical study of metabolites of natural products in animals

 Natural products and their derivatives are essential for various drug lead compounds. Finding new drugs from active natural product skeletons and optimizing lead compounds is critical to drug development. Some chemical components of Chinese medicines are of great interest to pharmaceutical R&D workers because they may have multiple pharmacological activities. 

Understanding the metabolism of natural products isolated from plants or synthesized using chemical methods in vivo can provide an individual material basis for pharmacodynamic and pharmacological studies of the drug. Rats or mice are usually used as animal models for the analysis of metabolites of compounds in vivo.

Drug metabolism is one of the critical factors affecting the action of drugs. Studying the pathways and stability of drug metabolism, the enzymes and kinetic parameters involved in metabolism, and the drug interaction problems caused by metabolism are necessary to find efficient and less toxic drugs. Thus it is necessary to study the metabolism of drugs. Conducting metabolite analysis of the drug in animals can provide favorable evidence to elucidate the mechanism of the drug's cure. For example, some researchers have performed metabolite analysis of the natural product brasilin in rats. Others have conducted metabolism studies of the natural product flavopiridol in rats and in vitro metabolism studies of flavopiridol in rat liver microsomes and intestinal flora incubation systems.

1.Metabolic study of brazilin in rats

Brazilin, also known as hematoxylin, is the main active component of hematoxylin and is commonly used as a natural pigment for pathological tissue staining. It has various pharmacological activities such as antibacterial, anti-inflammatory, hypoglycemic, immunomodulatory, etc. The study of its metabolites in animals provides a reference basis for its in-depth development and utilization.

Drug metabolism is the process of structural transformation of a drug during absorption or after entering the body circulation by the action of the intestinal flora, or the body's enzyme system is called metabolism or biotransformation, the product of which is the metabolite. Medicilon Pharmacokinetics Lab has passed the GLP certification by NMPA/ NMPA. Following the guiding principles of ICH, NMPA and FDA. The lab offers in vivo and in vitro pharmacokinetic tests according to our client's needs and provides them with complete sets of pharmacokinetic evaluation and optimization services.

Some researchers have investigated the metabolic pathways of brazilin hematoxylin by studying its metabolites in rats[1]. UPLC-Q-TOF-MS/MS was used to analyze, among others, biological samples (feces, urine, plasma, bile) from rats after gavage of brazilin (30 mg/kg-1) and then to screen and identify its possible metabolites. As a result, 23 metabolites were detected, produced by methylation, deoxygenation, hydrogen condensation, carboxylation, hydration, sulfation, and glucuronidation of brazilin hematoxylin in rats, with sulfation and glucuronidation predominating. This experiment is the first study on the metabolism of brassinosteroids in rats, which can provide a material basis for the pharmacodynamic and pharmacological study of brassinosteroids.

2. The metabolism of safranin in rats in vivo and in vitro

The natural product coptis is one of the main active components in the Chinese herb Huang Lian. Some pharmacological activities have been reported in the literature, such as inhibition of A-type monoamine oxidase, selective inhibition and dual inhibition of vascular smooth muscle cell proliferation, inhibition of osteoclast differentiation and function, particular regulation of multidrug-resistant proteins in vascular smooth muscle cells, antifungal, gastric mucosal protection, cytotoxicity, and myocardial protection.

Some investigators have investigated coptisine's in vivo and in vitro metabolites and their metabolic pathways[2]. In vivo metabolism was performed by single gavage of rats with safranine (dose 25 mg/kg-1), urine and feces from 0 to 48 h after administration, bile from 0 to 24 h, and plasma and brain tissue samples after 0.25, 1, and 2 h of administration; in vitro metabolism was performed by incubation with rat liver microsomes and intestinal flora; high-resolution HPLC-MS/MS techniques were used to The prototypes and metabolites of the drugs in the biological samples were identified using high-resolution HPLC-MS/MS.

The results showed that 17 metabolites, 11 metabolites in phase I and six metabolites in phase II, were found in rat urine, feces, bile, plasma, brain tissue, liver microsomal warm incubation, and intestinal flora warm incubation samples. In rats, these 17 metabolites were produced by hydroxylation, demethylation and dehydrogenation, sulfate esterification, and glucuronidation of flavopiridol. 

It was found that coptisine could undergo phase I and phase II metabolic reactions in rats, and the metabolites were mainly present in urine, and the leading metabolic site was the liver; coptisine was poorly absorbed in the gastrointestinal tract, metabolized little, and primarily excreted in the feces as a prototype, which provided a particular material basis for the pharmacodynamic and pharmacological studies of coptisine.

There are many methods for analyzing drug metabolites, including UPLC-Q-TOF-MS/MS in the text and the GC-Ms, nuclear magnetic resonance technique (NMR), LC-MS method, etc. Strengthening the research and application methods for in vivo analysis of drugs and drug metabolites to ensure more accurate and reliable drug analysis results can provide an essential guarantee for developing a pharmaceutical R&D business.

[1] Analysis of metabolites and metabolic pathways of brazilin in rats [J]

[2] HPLC-MS/MS analysis of coptisine metabolites in rats in vitro and in vivo [J]