Influence of pyrrolizidine alkaloids depletion upon the biological activity of Symphytum officinale L. extracts

Ethnopharmacological relevance: Comfrey (Symphytum officinale L., Boraginaceae) root preparations are used as both traditional remedies and therapeutic agents in treating pain and inflammation associated with joint, bone, and muscle ailments. Even though numerous phytochemicals contribute to the beneficial effects of comfrey, the presence of toxic pyrrolizidine alkaloids (PAs) overshadows its uses. Aim of the study: In this work, different PA-/mucilage-depleted/undepleted comfrey root extracts were subjected to detailed phytochemical characterization and biological evaluation. Materials and methods: The phytochemical profiling was performed by LC-HRMS/MS. The quantification of PAs and major phenolic compounds was carried out by LC-MS/MS and LC-DAD. Antioxidant and enzyme inhibitory activity was determined by in vitro free radical scavenging, ion reducing, metal chelating, cholinesterase, tyrosinase, amylase, and glucosidase assays. Using an ex vivo model of LPS-stimulated neutrophils, their viability (as measured by flow cytometry) and the release of IL-1fl, IL-8, and TNF-alpha were determined (ELISA assay). Results: 12 phenolic acids, six PAs, three organic acids, two fatty acids, and two sugars were identified in the obtained comfrey extracts. The PA-depleted materials contained PAs levels below 2 ppm, whereas the removal of mucilage increased the content of rosmarinic acid, globoidnan A, globoidnan B, and rabdosiin. PA-depletion did not significantly affect the antioxidant potential. However, the radical scavenging and metal reducing properties were higher in the mucilage-depleted extracts. Neither PA-depletion nor mucilage-depletion had considerable effects on the in vitro inhibitory activity of cholinesterases, tyrosinase, amylase, and glucosidase or release of ex vivo pro-inflammatory cytokines (e.g., IL-1fl, IL-8, and TNF-alpha) in LPS-stimulated neutrophils. Conclusions: In light of their superior safety profiles, PA-depleted comfrey extracts can be utilized further in cosmetic and pharmaceutical products.

Automated summary

In this study, comfrey root extracts with PA depletion and mucilage depletion were evaluated for their phytochemical characteristics and biological activities. The results showed that PA-depleted extracts had lower antioxidant activity, while mucilage-depleted extracts had higher radical scavenging and metal reducing abilities. Neither PA depletion nor mucilage depletion significantly affected the inhibitory activities of cholinesterases, tyrosinase, amylase, and glucosidase, as well as the release of pro-inflammatory cytokines from LPS-stimulated neutrophils. Therefore, PA-depleted comfrey extracts can be further utilized in cosmetic and pharmaceutical products.