Biotransformation of ginsenoside Rb1 and Rd to four rare ginsenosides and evaluation of their anti-melanogenic effects

Characterization and protein engineering of a novel UDP-glycosyltransferase involved in pseudoginsenoside Rt5 biosynthesis from Panax japonicus

As one of rare high-value ocotillol (OCT)-type ginsenosides, pseudoginsenoside Rt5 has been identified with significant pharmacological activities. UDP-glycosyltransferases (UGTs) play pivotal roles in catalyzing the transfer of a glycosyl moiety from a donor to an acceptor. In this study, the novel UGT, PjUGT10, was screened from the transcriptome database of Panax japonicus and identified with the enzymatic activity of transferring a glucosyl group on OCT to produce Rt5. The catalytic efficiency of PjUGT10 was further enhanced by employing site-directed mutation. Notably, the variant M7 exhibited a remarkable 6.16 × 103-fold increase in kcat/Km towards 20S,24R-ocotillol and a significant 2.02 × 103-fold increase to UDP-glucose, respectively. Moreover, molecular dynamics simulations illustrated a reduced distance between 20S,24R-ocotillol and the catalytic residue His15 or UDP-glucose, favoring conformation interactions between the enzyme and substrates. Subsequently, Rt5 was synthesized in an engineered Escherichia coli strain M7 coupled with a UDP-glucose synthetic system. This study not only shed light on the protein engineering that can enhance the catalytic activity of PjUGT10, but also established a whole-cell approach for the production of Rt5.

Advancements in enzymatic biotransformation and bioactivities of rare ginsenosides: A review

Ginsenoside, the principal active constituent of ginseng, exhibits enhanced bioavailability and medicinal efficacy in rare ginsenosides compared to major ginsenosides. Current research is focused on efficiently and selectively removing sugar groups attached to the major ginsenoside sugar chains to convert them into rare ginsenosides that meet the demands of medical industry and functional foods. The methods for preparing rare ginsenosides encompass chemical, microbial, and enzymatic approaches. Among these, the enzyme conversion method is highly favored by researchers due to its exceptional specificity and robust efficiency. This review summarizes the biological activities of different rare ginsenosides, explores the various glycosidases used in the biotransformation of different major ginsenosides as substrates, and elucidates their respective corresponding biotransformation pathways. These findings will provide valuable references for the development, utilization, and industrial production of ginsenosides.

Production of rare ginsenosides by biotransformation of Panax notoginseng saponins using Aspergillus fumigatus

Panax notoginseng saponins (PNS) are the main active components of Panax notoginseng. But after oral administration, they need to be converted into rare ginsenosides by human gut microbiota and gastric juice before they can be readily absorbed into the bloodstream and exert their effects. The sources of rare ginsenosides are extremely limited in P. notoginseng and other medical plants, which hinders their application in functional foods and drugs. Therefore, the production of rare ginsenosides by the transformation of PNS using Aspergillus fumigatus was studied in this research. During 50 days at 25 ℃ and 150 rpm, A. fumigatus transformed PNS to 14 products (1-14). They were isolated by varied chromatographic methods, such as silica gel column chromatography, Rp-C18 reversed phase column chromatography, semi-preparative HPLC, Sephadex LH-20 gel column chromatography, and elucidated on the basis of their 1H-NMR, 13C-NMR and ESIMS spectroscopic data. Then, the transformed products (1-14) were isolated and identified as Rk3, Rh4, 20 (R)-Rh1, 20 (S)-Protopanaxatriol, C-K, 20 (R)-Rg3, 20 (S)-Rg3, 20 (S)-Rg2, 20 (R)-R2, Rk1, Rg5, 20 (S)-R2, 20 (R)-Rg2, and 20 (S)-I, respectively. In addition, all transformed products (1-14) were tested for their antimicrobial activity. Among them, compounds 5 (C-K) and 7 [20 (S)-Rg3] showed moderate antimicrobial activities against Staphylococcus aureus and Candida albicans with MIC values of 6.25, 1.25 μg/mL and 1.25, 25 μg/mL, respectively. This study lays the foundation for production of rare ginsenosides.

Biotransformation approach to produce rare ginsenosides F1, compound Mc1, and Rd2 from major ginsenosides

The stems and leaves of Panax notoginseng contain high saponins, but they are often discarded as agricultural waste. In this study, the predominant ginsenosides Rg1, Rc, and Rb2, presented in the stems and leaves of ginseng plants, were biotransformed into value-added rare ginsenosides F1, compound Mc1 (C-Mc1), and Rd2, respectively. A fungal strain YMS6 (Penicillium sp.) was screened from the soil as a biocatalyst with high selectivity for the deglycosylation of major ginsenosides. Under the optimal fermentation conditions, the yields of F1, C-Mc1, and Rd2 were 97.95, 68.64, and 79.58%, respectively. This study provides a new microbial resource for the selective conversion of protopanaxadiol-type and protopanaxatriol-type major saponins into rare ginsenosides via the whole-cell biotransformation and offers a solution for the better utilization of P. notoginseng waste.

Preparation of isoquercitrin and rhamnose from readily accessible rutin by a highly specific recombinant α-L-rhamnosidase (r-Rha1)

Isoquercitrin has superior in vivo bioactivities with respect to its primary glycoside rutin. Its conventional preparation was ineffective, with large chemical consumption and many by-products. Rhamnose, a high value-added monosaccharide, is usually separated from acid hydrolytes of rutin. This study aimed to establish a novel enzymatic hydrolysis-based approach for their preparation. α-L-rhamnosidase was expressed in Pichia pastoris GS115 and applied to enzymolysis of rutin. Then, one-factor-at-a-time optimisation of hydrolysis conditions was performed. Two compounds were produced in 0.02 M HAc-NaAc buffer (pH4.50) containing α-L-rhamnosidase/rutin (1:4, w/w) at 60 °C. Consequently, 20.0 g/L rutin was completely hydrolysed in 2 hrs, and isoquercitrin was obtained after purification by HPD-100 resin. Additionally, rhamnose was enriched by decolorisation and crystallisation. MD simulation analysis suggested that rutin was catalysed on the hydrophobic surface of r-Rha1 with van-der-Waals force being main driving force. This strategy is an efficient approach for preparation of isoquercitrin and rhamnose.