# Biological mechanisms of sodium nitroprusside in enhancing quality of Radix Paeoniae Rubra and Radix Paeoniae Alba

## TL;DR

This study shows how sodium nitroprusside improves the medicinal quality of two paeony root varieties by boosting their secondary metabolites through a ROS-mediated mechanism.

## Contribution

The study identifies a novel NO-ROS-secondary metabolism regulatory axis for quality improvement in medicinal plants.

## Key findings

- SNP treatment increases secondary metabolites in RRP and RAP germplasm.
- ROS acts as a key mediator linking exogenous NO to secondary metabolism.
- Scavenging ROS reduces SNP-induced metabolite accumulation.

## Abstract

Both Paeoniae Radix Alba (RAP) and Paeoniae Radix Rubra (RRP) are important botanical drugs used in Asian countries. Although they are both derived from the roots of Paeonia lactiflora Pall., they exhibit distinct pharmacological properties due to differences in germplasm and processing methods. Due to overwhelming market demand, the cultivated varieties have become the primary source to compensate for insufficient wild resources, which have led to decreased medicinal quality. This study aimed to address this quality decline and put forward a hypothesis that exogenous nitric oxide (NO) induces the reactive oxygen species (ROS)-mediated enhancement of secondary metabolism in fresh roots of P. lactiflora, thereby improving medicinal quality.

Fresh roots of P. lactiflora germplasm for Paeoniae Radix Rubra production (RRP-germplasm) and for Paeoniae Radix Alba production (RAP-germplasm) were treated with sodium nitroprusside (SNP) at concentrations of 0.0, 0.1, 0.5, or 2.5 mmol/L to induce ROS bursts.

In the fresh roots of RRP-germplasm treated with 0.5 mmol/L SNP, the secondary metabolites paeoniflorin, albiflorin, oxypaeoniflorin, gallic acid, catechin, and paeonol were elevated by 19.1%, 205.4%, 115.4%, 19.9%, 201.0%, and 585.2%, respectively, and in the fresh roots of RAP-germplasm treated with 2.5 mmol/L SNP, the major secondary metabolites paeoniflorin, albiflorin, oxypaeoniflorin, gallic acid, catechin, and benzoic acid showed increases of 25.4%, 70.4%, 95.1%, 6.7%, 86.5%, and 33.6%, respectively. Moreover, experiments involving combined treatment with SNP and ROS scavengers demonstrated that ROS act as the key mediator linking exogenous NO to the secondary metabolism of P. lactiflora: scavenging ROS significantly attenuated the SNP-induced accumulation of target secondary metabolites.

Combined with the above findings of SNP promoting secondary metabolite synthesis, this study confirms that exogenous NO can improve the quality of cultivated RAP and RRP via ROS-mediated secondary metabolism, and clarifies the NO-ROS-secondary metabolism regulatory axis, offering insights for other medicinal plants’ quality improvement.