Biotransformation of American Ginseng Stems and Leaves by an Endophytic Fungus Umbelopsis sp. and Its Effect on Alzheimer's Disease Control

Abstract

Background: Common ginsenosides can be transformed into rare ginsenosides through microbial fermentation, and some rare ginsenosides can prevent Alzheimer's disease (AD). This study aimed to transform common ginsenosides into rare ginsenosides through solid-state fermentation of American ginseng stems and leaves (AGSL) by an endophytic fungus and to explore whether fermented saponin extracts prevent AD.

Methods: The powders of AGSL were fermented in a solid state by endophytic fungus. Total saponins were extracted from fermentation products using the methanol extraction method. The types of saponins were analyzed by liquid chromatography mass spectrometry (LC/MS). The Aβ42 concentration and β-secretase activity were measured by ELISA for the prevention of AD.

Results: After AGSL was fermented by an endophytic fungus NSJG, the total saponin concentration of the fermented extract G-SL was higher than the unfermented CK-SL. Rare ginsenoside Rh1 was newly produced and the yield of compound K (561.79%), Rh2 (77.48%), and F2 (40.89%) was increased in G-SL. G-SL had a higher inhibition rate on Aβ42 concentration (42.75%) and β-secretase activity (42.22%) than CK-SL, possibly because the rare ginsenoside Rh1, Rh2, F2, and compound K included in it have a strong inhibitory effect on AD.

Conclusion: The fermented saponin extracts of AGSL show more inhibition effects on AD and may be promising therapeutic drugs or nutrients for AD.

Keywords: Alzheimer’s disease; American ginseng stems and leaves; biotransformation; endophytic fungus; solid-state fermentation.

Figure 1

Phylogenetic tree characterization of endophytic fungus NSJG. The numbers on the nodes represent branch confidence values. The scale bar indicates a 2% estimated sequence divergence.

Figure 2

Total saponin concentration of CK-SL and G-SL. CK-SL represents a control group without fermentation. G-SL represents fermentation by NSJG and American ginseng stems and leaves. Data are presented as means ± SD, n = 3.

Figure 3

The transformation pathway of ginsenosides. Glc is β-D-glucopyranosyl; Arap is α-L-arabinopyranosyl; Rha is α-L-rhamnopyranosyl. Arrows represent the direction of ginsenoside transformation. The numbers represent the position of carbon in the chemical formula.

Figure 4

Cell viability at different times and concentrations. (a) Cell viability of ginsenoside Rb1 at 12, 24, and 48 h. (b) Cell viability of G-SL and CK-SL at different concentrations. (c) Cell viability of rare ginsenosides at different concentrations.

Figure 5

Effects on Aβ42 concentration and β-secretase activity by fermented extracts and rare ginsenosides. (a) Aβ42 concentration of CK-SL at different concentrations. (b) β-secretase activity of CK-SL at different concentrations. (c) The inhibition rate of Aβ42 and β-secretase by CK-SL at different concentrations. (d) Aβ42 concentration of G-SL at different concentrations. (e) β-secretase activity of G-SL at different concentrations. (f) The inhibition rate of Aβ42 and β-secretase by G-SL at different concentrations. (g) Aβ42 concentration by four rare ginsenosides. (h) β-secretase activity by four rare ginsenosides. Data are presented as means ± SD, n = 3. * p < 0.05, ** p < 0.01, *** p < 0.001.