# The correlation between characteristics and pharmacological effects of monoterpene glycosides and tannins in Radix Paeoniae Alba

## TL;DR

This study explores how two compounds in Radix Paeoniae Alba, monoterpene glycosides and tannins, contribute to its medicinal effects despite their poor absorption in the body.

## Contribution

The study systematically reviews the pharmacological roles and mechanisms of monoterpene glycosides and tannins in Radix Paeoniae Alba, emphasizing their distinct bioavailability and effects.

## Key findings

- Monoterpene glycosides and tannins in Radix Paeoniae Alba have poor bioavailability due to gut metabolism and hydrophobicity.
- Monoterpene glycosides exert anti-inflammatory, immunomodulatory, and neuromodulatory effects after intestinal absorption.
- Tannins remain localized in the digestive system due to their inability to cross the intestinal barrier.

## Abstract

The pharmacodynamic material basis constitutes the central element of traditional Chinese medicine (TCM) in disease treatment. By summarizing the active compounds' characteristics, bioavailability, pharmacological effects, and molecular mechanisms, we can explain the complex interactions between TCMs and diseases. Previous studies have demonstrated that monoterpene glycosides and tannins are related to the pharmacological activity of Radix Paeoniae Alba (RPA). However, research on RPA has primarily focused on monoterpene glycosides, and the functional role of tannins in RPA has received little attention. Observations from animal studies indicate that monoterpene glycosides and tannins exhibit poor bioavailability. Carboxylesterase, produced by gut microbiota, is crucial for metabolizing these compounds in the intestine. Monoterpene glycosides and their gut metabolites can be absorbed into the bloodstream, exerting various pharmacological effects, including anti-inflammatory, immunomodulatory, and neuromodulator activities. In contrast, tannins consist of highly hydrophobic polyphenols that form insoluble protein-tannin complexes. Due to their inability to cross the intestinal barrier, tannins primarily exert localized pharmacological effects within the digestive system. This study systematically reviews the pharmacological activities and mechanisms of monoterpene glycosides and tannins in RPA, while establishing their therapeutic contributions to the herb's pharmacological effects.

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•Monoterpene glycosides and tannins are the two main compounds of Radix Paeoniae Alba, which all have poor bioavailability.•A key intestinal carboxylesterase transformed monoterpene glycosides and tannins.•Monoterpene glycosides exert anti-inflammatory, immunomodulatory, and neuromodulatory pharmacological effects.•Tannins have limited bioavailability due to hydrophobicity, focusing their effects on the digestive system.•Glycosides and tannins' activity are related to Radix Paeoniae Alba's pharmacological effects.

Monoterpene glycosides and tannins are the two main compounds of Radix Paeoniae Alba, which all have poor bioavailability.

A key intestinal carboxylesterase transformed monoterpene glycosides and tannins.

Monoterpene glycosides exert anti-inflammatory, immunomodulatory, and neuromodulatory pharmacological effects.

Tannins have limited bioavailability due to hydrophobicity, focusing their effects on the digestive system.

Glycosides and tannins' activity are related to Radix Paeoniae Alba's pharmacological effects.