Abstract
Eugenyl-β-D-glucopyranoside, also referred to as Citrusin C, is a natural glucoside found among others in cloves, basil and cinnamon plants. Eugenol in a form of free aglycone is used in perfumeries, flavourings, essential oils and in medicinal products. Synthetic Citrusin C was incubated with human saliva in several in vitro models together with substrate-specific enzyme and antibiotics (clindamycin, ciprofloxacin, amoxicillin trihydrate and potassium clavulanate). Citrusin C was detected using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Citrusin C was completely degraded only when incubated with substrate-specific A. niger glucosidase E.C 3.2.1.21 (control sample) and when incubated with human saliva (tested sample). The addition of antibiotics to the above-described experimental setting, stopped Citrusin C degradation, indicating microbiologic origin of hydrolysis observed. Our results demonstrate that Citrusin C is subjected to complete degradation by salivary/oral cavity microorganisms. Extrapolation of our results allows to state that in the human oral cavity, virtually all β-D-glucosides would follow this type of hydrolysis. Additionally, a new method was developed for an in vivo rapid test of glucosidase activity in the human mouth on the tongue using fluorescein-di-β-D-glucoside as substrate. The results presented in this study serve as a proof of concept for the hypothesis that microbial hydrolysis path of β-D-glucosides begins immediately in the human mouth and releases the aglycone directly into the gastrointestinal tract.
Highlights
Knowledge concerning potential mechanism of natural release of biologically active aglycone by microbial enzyme hydrolysis of β-D-glucosidic bond from the paternal glucoside molecule on human tongue is extremely scanty, as well as about rapid methods for determining β-glucosidase activity in the oral cavity
It has been thought that hydrolysis of dietary β-glucosides takes place in the large intestine due to the colon microflora [1]
Other glycosides in the determination of enzymatic activities are known, such as 4MU-β-D-Glucoside used in Gaucher disease as an indicator, or the more toxic PNP-β-D-glucoside
Summary
Knowledge concerning potential mechanism of natural release of biologically active aglycone by microbial enzyme hydrolysis of β-D-glucosidic bond from the paternal glucoside molecule on human tongue is extremely scanty, as well as about rapid methods for determining β-glucosidase activity in the oral cavity. It has been thought that hydrolysis of dietary β-glucosides (flavonoids and isoflavones) takes place in the large intestine due to the colon microflora [1]. Metabolites of some flavonols and isoflavones appear in plasma within 30 min of ingestion, indicating rapid absorption in the small intestine [2,3]. In one study [4], it was shown that the cell-free extracts form human small intestine and liver had β-glucosidase activity towards flavonoid and isoflaflavone glycosides. Data presented by other authors included the hydrolysis of rutin in cell-free extracts collected from human fecal flora and saliva [5]
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