Sylwia Godlewska

Symphytum officinale L. (Boraginaceae) is a plant with proven anti-inflammatory and analgesic activity on the musculoskeletal system. The traditional use of comfrey primarily refers to its roots, although some literature also mentions the leaves as an alternative plant material. Comparing the therapeutic potential of both plant materials requires additional data on the chemical composition of S. officinale leaves and their biological properties. The aim of the study was to analyze polyphenols in comfrey leaves of different origins and to assess their antioxidant and anti-inflammatory potential against comfrey roots, also collected from different sources. Polyphenol profiles were recognized by 2D TLC and HPLC-DAD-ESI-MS methods, and quantitative analysis was performed by the HPLC-UV/Vis (high performance liquid chromatograph with-ultraviolet/visible detection) method. The antioxidant activity was assessed using DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (ferric reducing antioxidant power), and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline- 6-sulfonic acid) diammonium salt) assays, and for leaves also using the TLC-DB (thin layer chromatography-direct bioautography) technique with the DPPH radical. Chemometric analysis to assess the relationship between the antioxidant activity and the origin of comfrey plant raw materials was performed. Factor analysis (FA) confirmed that geographic origin and cultivation conditions influenced the antioxidant content of both plant raw materials. The study results indicate that comfrey leaves can substitute for comfrey roots containing not only caffeic acid derivatives but also flavonoids, and exhibiting stronger antioxidant activity.

Rhododendron tomentosum Harmaja is a marsh plant known for its high content of bioactive components, including essential oil, flavonoids, and phenolic acids. In the current work, the effects of cultivation mode (agar, liquid stationary, shake flask, and temporary immersion) and experiment duration (30, 60, and 90 days) on the growth and contents of non-volatile phenolics in Rhododendron tomentosum microshoots were investigated. Agar and liquid stationary cultures provided the highest dry biomass yield per liter, but their dry weight productivities per day were the lowest among the tested systems. Agitated and temporary immersion cultures, on the other hand, were the most productive in terms of fresh and dry biomass yield per day. LC-DAD-ESI-MS analysis of extracts from microshoots and wild-grown plants revealed similarities in phenolic composition: in both cases, the presence of catechin, chlorogenic acid, and flavonoids of flavonol type (mainly glycosides of quercetin and myricetin) was confirmed. The qualitative composition of the phenolic fraction was not affected by experiment duration and cultivation mode. As determined by HPLC analysis, shake flask and temporary immersion cultures were characterized by the highest phenolic contents: up to 37.5 and 26 mg/g dry weight, respectively. The maximum productivities of the above systems were equal to 18 and 13.5 mg/L/d, respectively.

Poplar leaves (Populi folium) are a herbal remedy traditionally used for the treatment of rheumatic diseases and prostate inflammation. The aim of our study was a comprehensive identification of secondary metabolites occurring in the leaves of Populus alba, Populus × candicans, and Populus nigra, in order to search for a source of raw plant material rich in active compounds. Total salicylate (TSC), flavonoid (TFC), and phenolic compound (TPC) contents were determined, and the antioxidant potential was assessed using DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline- 6-sulfonic acid) diammonium salt), and FRAP (ferric reducing antioxidant power) assays as well as 2D-TLC (two-dimensional thin layer chromatography) bioautography using DPPH, riboflavin-light-NBT (nitro blue tetrazolium chloride), and xanthine oxidase inhibition tests. Secondary metabolites present in the analyzed poplar leaves were identified under the developed HPLC-DAD-ESI/MS (high performance liquid chromatography with photodiode array detection and electrospray ionization mass spectrometric detection analysis conditions and using the 2D-TLC method. Among the 80 identified compounds, 13 were shown for the first time in the genus Populus. The most diverse and similar set of flavonoids characterized the leaves of P. × candicans and P. nigra, while numerous salicylic compounds were present in the leaves of P. alba and P. × candicans. All analyzed leaves are a rich source of phenolic compounds. The highest flavonoid content was found in the leaves of P. × candicans and P. nigra, while the leaves of P. alba were characterized by the highest content of salicylates. All examined poplar leaves demonstrated antioxidant potential in all the assays used, which decreased in the following order: P. nigra, P. × candicans, P. alba.

Comfrey (Symphytum officinale L.) has a long tradition of use in the treatment of musculoskeletal disorders. However, due to hepatotoxic pyrrolizidine alkaloids (PAs), the EMA restricts the use of comfrey root (CR) to external use only and for short periods of time. Recent studies indicate a low permeability of PAs across the skin, calling into question the safety of topical application of products containing comfrey preparations. The aim of our work was to develop and validate an HPLC method enabling the separation of isomeric PAs from comfrey and, on this basis, to assess the potential toxicity of CR and comfrey leaf (CL) obtained from various Polish sources. The qualitative and quantitative analysis of PAs via HPLC-MS/MS was performed in MRM mode. The results obtained confirmed a lower content of PAs in CL than in CR and showed a wide variation in the composition of PAs in CR, with a much more stable profile of PAs in CL. Factor analysis confirmed that CRs and CLs differ in PA content, which is influenced by the growth conditions and geographical origin. The determined concentrations of PAs prove that in some CRs available on the Polish herbal market, the content of PAs may exceed the daily dose considered safe.

Urolithins are bioactive compounds generated in human and animal intestines because of the bacterial metabolism of dietary ellagitannins (and their constituent, ellagic acid). Due to their multidirectional effects, including anti-inflammatory, antioxidant, anti-cancer, neuroprotective, and antiglycative properties, urolithins are potential novel therapeutic agents. In this study, while considering the future possibility of using urolithins to improve podocyte function in diabetes, we assessed the results of exposing mouse podocytes cultured in normal (NG, 5.5 mM) and high (HG, 25 mM) glucose concentrations to urolithin A (UA) and urolithin B (UB). Podocytes metabolized UA to form glucuronides in a time-dependent manner; however, in HG conditions, the metabolism was lower than in NG conditions. In HG milieu, UA improved podocyte viability more efficiently than UB and reduced the reactive oxygen species level. Both types of urolithins showed cytotoxic activity at high (100 µM) concentration. The UA upregulated total and surface nephrin expression, which was paralleled by enhanced nephrin internalization. Regulation of nephrin turnover was independent of ambient glucose concentration. We conclude that UA affects podocytes in different metabolic and functional aspects. With respect to its pro-survival effects in HG-induced toxicity, UA could be considered as a potent therapeutic candidate against diabetic podocytopathy.

Carnivorous plants are exemplary natural sources of secondary metabolites with biological activity. However, the therapeutic antimicrobial potential of these compounds is limited due to intrinsic resistance of selected bacterial pathogens, among which Pseudomonas aeruginosa represents an extreme example. The objective of the study was to overcome the intrinsic resistance of P. aeruginosa by combining silver nanoparticles (AgNPs) with secondary metabolites from selected carnivorous plant species. We employed the broth microdilution method, the checkerboard titration technique and comprehensive phytochemical analyses to define interactions between nanoparticles and active compounds from carnivorous plants. It has been confirmed that P. aeruginosa is resistant to a broad range of secondary metabolites from carnivorous plants, i.e., naphthoquinones, flavonoids, phenolic acids (MBC = 512 µg mL⁻¹) and only weakly sensitive to their mixtures, i.e., extracts and extracts’ fractions. However, it was shown that the antimicrobial activity of extracts and fractions with a significant level of naphthoquinone (plumbagin) was significantly enhanced by AgNPs. Our studies clearly demonstrated a crucial role of naphthoquinones in AgNPs and extract interaction, as well as depicted the potential of AgNPs to restore the bactericidal activity of naphthoquinones towards P. aeruginosa. Our findings indicate the significant potential of nanoparticles to modulate the activity of selected secondary metabolites and revisit their antimicrobial potential towards human pathogenic bacteria.