Abstract
Functional bacteria that could biotransform triterpenoids may exist in the diverse microflora of fish intestines. Ganoderic acid A (GAA) is a major triterpenoid from the medicinal fungus Ganoderma lucidum. In studying the microbial biotransformation of GAA, dozens of intestinal bacteria were isolated from the excreta of zebrafish. The bacteria’s ability to catalyze GAA were determined using ultra-performance liquid chromatography analysis. One positive strain, GA A07, was selected for functional studies. GA A07 was confirmed as Bacillus sp., based on the DNA sequences of the 16S rRNA gene. The biotransformed metabolite was purified with the preparative high-performance liquid chromatography method and identified as GAA-15-O-β-glucoside, based on the mass and nuclear magnetic resonance spectral data. The present study is the first to report the glycosylation of Ganoderma triterpenoids. Moreover, 15-O-glycosylation is a new microbial biotransformation of triterpenoids, and the biotransformed metabolite, GAA-15-O-β-glucoside, is a new compound.
Highlights
Ganoderma lucidum is known to the Chinese as “Lingzhi”, which has been used as a diet therapy in traditional Chinese medicine for more than 2000 years
To study the biotransformation of Ganoderma triterpenoid ganoderic acid A (GAA), dozens of intestinal bacteria were isolated with the plating method and cultivated in broth with GAA
In the GAA biotransformation using the GA A07 strain, only one metabolite, which was glycosylated at the C-15 hydroxyl group, was observed (Figures 1 and 3), the other C-7 hydroxyl or C-26 carboxyl groups on the GAA structure were available for glycosylation
Summary
Ganoderma lucidum is known to the Chinese as “Lingzhi”, which has been used as a diet therapy in traditional Chinese medicine for more than 2000 years. G. lucidum is used in the prevention or treatment of many diseases, especially for immunomodulatory and antitumor activities [1]. G. lucidum contains many bioactive components, where polysaccharides and triterpenoids are the main bioactive components. More than 300 different triterpenoids have been identified from Ganoderma spp. All Ganoderma triterpenoids are the tetracyclic lanostane type. Among the Ganoderma triterpenoids, ganoderic acid A (GAA) was the first identified [3]. GAA has been identified with some bioactivities, including antitumor [4,5,6], anti-inflammatory [7], antinociceptive [8], and antioxidative [9] activities
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