Enzymatic Biotransformation of Balloon Flower Root Saponins into Bioactive Platycodin D by Deglucosylation with Caldicellulosiruptor bescii β-Glucosidase.

Tae-Geun Kil,Kyung-Chul Shin,Su-Hwan Kang,Tae-Hun Kim,Deok-Kun Oh

doi:10.3390/ijms20163854

Abstract

Platycodin D (PD), a major saponin (platycoside) in Platycodi radix (balloon flower root), has higher pharmacological activity than the other major platycosides; however, its content in the plant root is only approximately 10% (w/w) and the productivities of PD by several enzymes are still too low for industrial applications. To rapidly increase the total PD content, the β-glucosidase from Caldicellulosiruptor bescii was used for the deglucosylation of the PD precursors platycoside E (PE) and platycodin D3 (PD3) in the root extract into PD. Under the optimized reaction conditions, the enzyme completely converted the PD precursors into PD with the highest productivity reported so far, increasing the total PD content to 48% (w/w). In the biotransformation process, the platycosides in Platycodi radix were hydrolyzed by four pathways: deapiosylated (deapi)-PE → deapi-PD3 → deapi-PD, PE → PD3 → PD, polygalacin D3 → polygalacin D, and 3″-O-acetyl polygalacin D3 → 3″-O-acetyl polygalacin D.

Highlights

Platycodon grandiflorum, a common vegetable commonly known as “balloon flower”, has been used as a health food to make side dishes, desserts, teas, and flavored liquors in Northeast Asia
Substrate Specificity of C. bescii β-Glucosidase for Platycosides β-Glucosidase from the hyperthermophilic bacterium C. bescii has been used for the complete biotransformation of protopanaxadiol-type saponins into 20-O-β-glucopyranosyl-20(S)-protopanaxadiol by deglycosylation because of its high hydrolytic activity
The highest specific activity was observed with deapi-platycoside E (PE), followed by PE, polygalacin D3, platycodin D3 (PD3), and deapi-PD3, which were converted into deapi-PD3 and deapi-platycodin D (PD), PD3 and PD, polygalacin D, PD, and deapi-PD, respectively

Summary

Introduction

Platycodon grandiflorum, a common vegetable commonly known as “balloon flower”, has been used as a health food to make side dishes, desserts, teas, and flavored liquors in Northeast Asia. It has been used as a traditional herbal medicine for its antibacterial activity [1]. Interest in the saponins of Platycodi radix (the root of Platycodon grandiflorum), named platycosides, has increased owing to the new discovery of their pharmacological potential for treating geriatric diseases such as diabetes [2] and hyperlipidemia [3]. One sugar moiety (usually comprising 1–3 β-glucose molecules) is linked to C-3 in the aglycone by a glycosidic bond, whereas the other sugar moiety (an oligosaccharide residue of arabinose, rhamnose, xylose, and apiose) is bound to C-28 by an ester linkage (Figure 1) [9]

Methods

Results

Conclusion