Metabolic Fate of Depsides and Alkaloid Constituents in Aqueous Extracts from Mercurialis perennis L. during Fermentation

Abstract

Dog's mercury (Mercurialis perennis L.) is an old medicinal plant, nowadays used in complementary medicine. Aqueous fermented extracts of the plant are being mainly applied in remedies to treat external inflammations, but a thorough phytochemical characterization is still lacking. Therefore, the conversion of characteristic compound classes from M. perennis extracts during fermentation and storage was investigated. The microbial transformation of the two main depsides phaselic acid (=(2R)-O-[(E)-caffeoyl]malic acid; 1) and mercurialis acid (=(2R)-[(E)-caffeoyloxy]glutaric acid; 2) was monitored by HPLC-DAD. The degradation followed a second-order kinetic, and the calculated half-life periods of both constituents were 67 and 30 months, respectively. Several depside metabolites were detected by GC/MS in AcOEt extracts as (t) BuMe2 Si (TBDMS) derivatives after derivatization, mainly dihydrocinnamic acids. Moreover, numerous α-hydroxy acids were found, allegedly as degradation products from amino acids or peptides. The microbial alteration of the main alkaloid hermidin was also examined. After three days of fermentation, three novel N-metabolites were formed and thoroughly assigned in CH2 Cl2 extracts as a mixture of 3-ethylhermidin, 3-ethylhermidin quinone, and (E/Z)-3-ethylidenehermidin by GC/MS and NMR methods, as well as by means of total synthesis. A mechanism for the formation of these N-metabolites starting from dimeric hermidin oxidation products is proposed. The obtained results reveal the complex pathways plant constituents may undergo during the fermentation of the extracts.

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

“…In the AcOEt extracts of an unfermented aqueous sample (t = 0 days, Figure 2A (Table 2) indicate these compounds to be methoxy-N-methylpiperidione derivatives, amplified by one C1 unit. Based on mass spectral similarities to literature data of ethylhermidin and ethylhermidin quinone (Mw 199 and 197 Da, respectively), formerly detected in M. perennis extracts fermented with a mixed LAB flora [30], we conclude that the novel constituents are methylhermidin (6) and methylhermidin quinone (7) (Figure 1). Starting from hermidin (1), the spontaneously formed oxidation products 3 and 4 (Figure After sterile filtration, the obtained aqueous extracts (pH 7.2) were incubated either with the LAB strain PP1 or LP1.…”

“…Meanwhile, numerous constituents of M. perennis and further Mercurialis species have been identified, e.g., the piperidine-dione alkaloid hermidin (1) [24][25][26], cinnamic acid depsides, flavonoids [27] and further low-molecular phenolics, terpenoids [26] and n-alkyl resorcinols [23,28,29]. Recently, we reported a first study on the metabolism of constituents upon spontaneous fermentation of M. perennis extracts, as a result of the action of the wild LAB flora [30]. Even though these investigations revealed the formation of novel metabolites, some of the enzymatic conversion pathways, especially of the N-containing compounds, are still poorly understood.…”

Lipid and Phenolic Constituents from Seeds of Hypericum perforatum L. and Hypericum tetrapterum Fr. and their Antioxidant Activity

“…GC/MS analyses of fraction I were carried out according to Lorenz et al . with a Perkin–Elmer 500 gas chromatograph coupled to a single quadrupole mass detector.…”

“…For comparison with authentic references, mangiferin, 1,3,5,6‐THX, and 1,3,6,7‐THX were dissolved in methanol. For GC/MS analyses, silylation of constituents was performed according to methods previously described in literature to obtain the corresponding trimethylsilyl derivatives. For this purpose, fraction II (6 mg) or purified compounds (1 mg) were dissolved in 0.5 ml of DMF and treated with 300 μl of BSTFA at 105 °C for 15 min and subsequently injected into the GC/MS system.…”

“…The free radical scavenging activities of the methanol seed extracts were determined by the 1,1′‐diphenyl‐2‐picrylhydrazyl (DPPH) assay according to a protocol previously described . Briefly, fraction II (5.0 mg for H. perforatum and 10.0 mg for H. tetrapterum , resp.)…”