Conversion of Plant Secondary Metabolites upon Fermentation of Mercurialis perennis L. Extracts with two Lactobacteria Strains

Abstract

Microbial fermentation of plant extracts with Lactobacteria is an option to obtain microbiologically stable preparations, which may be applied in complementary medicine. We investigated the metabolic conversion of constituents from Mercurialis perennis L. extracts, which were prepared for such applications. For this purpose, aqueous extracts were inoculated with two Lactobacteria strains, namely Pediococcus sp. (PP1) and Lactobacillus sp. (LP1). Both were isolated from a fermented M. perennis extract and identified by 16S rRNA sequencing. After 1 day of fermentation, an almost complete conversion of the genuine piperidine-2,6-dione alkaloids hermidine quinone (3) and chrysohermidin (4)—both of them being oxidation products of hermidin (1) —was observed by GC-MS analysis, while novel metabolites such as methylhermidin (6) and methylhermidin quinone (7) were formed. Surprisingly, a novel compound plicatanin B (bis-(3-methoxy-1N-methylmaleimide); 8) was detected after 6 days, obviously being formed by ring contraction of 4. An intermediate of a postulated reaction mechanism, isochrysohermidinic acid (14), could be detected by LC-MS. Furthermore, an increase in contents of the metabolite mequinol (4-methoxyphenol; 9) upon fermentation points to a precursor glycoside of 9, which could be subsequently detected by GC-MS after silylation and identified as methylarbutin (15). 15 is described here for M. perennis for the first time.

Evaluation of Geum urbanum L. Extracts with Respect to Their Antimicrobial Potential

“…It has been demonstrated in previous studies that the fermentation of medicinal plant extracts may go along with significant changes in the metabolite profile in the first days [29,13] . In contrast, aqueous extracts from wood avens roots are extremely stable regarding their metabolite profile.…”

“…After 24 h at 4 °C the extract was manually pressed using a cotton cloth and filtered over Celite. Afterwards, the filtrates were inoculated with overnight cultures of Pediococcus pentosaceus (PP1; GenBank accession number: MK841045.1; Sequence length (bp): 1441; Closest relative in National Center for Biotechnology Information: Pediococcus pentosaceus strain CMGB−L16, MF348228.1; Similarity 100 %) in MRS broth (1.5 mL each) and incubated at 33 °C [13] . The PP1 strain was identified by 16S rRNA analysis [13] .…”

“…Afterwards, the filtrates were inoculated with overnight cultures of Pediococcus pentosaceus (PP1; GenBank accession number: MK841045.1; Sequence length (bp): 1441; Closest relative in National Center for Biotechnology Information: Pediococcus pentosaceus strain CMGB−L16, MF348228.1; Similarity 100 %) in MRS broth (1.5 mL each) and incubated at 33 °C [13] . The PP1 strain was identified by 16S rRNA analysis [13] . For semi‐quantitative monitoring at different stages, fermentation was performed in quadruplicate (4×60 mL).…”

“…Fermentation is a viable method to produce stable medicinal plant extracts, which has been laid down in the official German Homoeopathic Pharmacopoeia (GHP) [8–13] . Such fermentation processes based on lactofermentation are well‐known from food production [14–17] .…”

Characterization of Secondary Metabolites in Flowers of Sanguisorba officinalisL. by HPLC‐DAD‐MSn and GC/MS

“…The instruments were controlled by Agilent LC 3D systems (Rev. B01.03SR1 (204)) and EsquireControl software (V7.1) . Anthocyanins were analyzed in the positive‐ion mode with the following device parameters: dry gas (N 2 ) flow: 8.00 L/min; nebulizer pressure: 40 psi; capillary temperature: 350 °C; for the negative‐ and positive‐ion modes, MS spectra were recorded in a range of m/z 50 to 1500 with a compound stability and trap drive level of 100 % …”