Gentisyl alcohol and homogentisic acid: Plasmodium falciparum dihydroorotate dehydrogenase inhibitors isolated from fungi

The chemical and metabolite profiles of Gualou-Xiebai-Banxia decoction, a classical traditional Chinese medicine formula, by using high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and in-house software

ETHNOPHARMACOLOGICAL RELEVANCE

Gualou-Xiebai-Banxia decoction (GXBD) was a classical traditional Chinese medicine formula for the treatment of coronary heart disease. However, the current study on the chemical and metabolite profiles of GXBD did not follow the ancient prescription and extraction method, which hindered the discovery of effective compounds and quality control.

MATERIALS AND METHODS

In this study, we prepared GXBD by ancient prescription and extraction methods, and then analysed the chemical components and xenobiotics of GXBD in vivo using high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and in-house software.

RESULTS

49 chemical constituents were preliminarily identified, including 7 terpenoids, 6 flavonoids, 5 alkaloids, 17 organic acids, 8 steroids and steroidal saponins, 2 nucleosides and 4 other types of compounds, of which 10 constituents were confirmed unambiguously with authentic standards. Moreover, 129 metabolites were tentatively identified, including 83 metabolites in plasma, 39 metabolites in urine, 25 metabolites in bile and 9 metabolites in feces. Our study speculated that luteolin, adenosine, vanillic acid and curbitacin B might be possible effective components of GXBD for the treatment of coronary heart disease. Dehydration, deglycosylation, dehydrogenation, acetylation and taurine regulation were the main biotransformation reactions of GXBD.

CONCLUSION

Our results provided an important basis for the discovery of effective compounds and quality control of GXBD. In addition, in-house software was an useful tool for identifcation of metabolites.

Exploring natural microbial resources for the discovery of anti-malarial compounds

Microorganisms in nature are highly diverse biological resources, which can be explored for drug discovery. Some countries including Brazil, Columbia, Indonesia, China, and Mexico, which are blessed with geographical uniqueness with diverse climates and display remarkable megabiodiversity, potentially provide microorganismal resources for such exploitation. In this review, as an example of drug discovery campaigns against tropical parasitic diseases utilizing microorganisms from such a megabiodiversity country, we summarize our past and on-going activities toward discovery of new antimalarials. The program was held in a bilateral collaboration between multiple Indonesian and Japanese research groups. In order to develop a new platform of drug discovery utilizing Indonesian bioresources under an international collaborative scheme, we aimed at: 1) establishment of an Indonesian microbial depository, 2) development of robust enzyme-based and cell-based screening systems, and 3) technology transfer necessary for screening, purification, and identification of antimalarial compounds from microbial culture broths. We collected, characterized, and deposited Indonesian microbes. We morphologically and genetically characterized fungi and actinomycetes strains isolated from 5 different locations representing 3 Indonesian geographical areas, and validated genetic diversity of microbes. Enzyme-based screening was developed against two validated mitochondrial enzymes from Plasmodium falciparum, dihydroorotate dehydrogenase and malate:quinone oxidoreductase, while cell-based proliferation assay was developed using the erythrocytic stage parasite of 3D7 strain. More than 17 thousands microbial culture extracts were subjected to the enzyme- and cell-based screening. Representative anti-malarial compounds discovered in this campaign are discussed, including a few isolated compounds that have been identified for the first time as anti-malarial compounds. Our antimalarial discovery campaign validated the Indonesian microbial library as a powerful resource for drug discovery. We also discuss critical needs for selection criteria for hits at each stage of screening and hit deconvolution such as preliminary extraction test for the initial profiling of the active compounds and dereplication techniques to minimize repetitive discovery of known compounds.