Assessment of cytotoxicity exerted by leaf extracts from plants of the genus Rhododendron towards epidermal keratinocytes and intestine epithelial cells

Abstract

BackgroundRhododendron leaf extracts were previously found to exert antimicrobial activities against a range of Gram-positive bacteria. In this study, we investigated which of the extracts with these antimicrobial properties would be best suited for further exploitation. Specifically, the project aims to identify biologically active compounds that affect bacterial but not mammalian cells when applied in medical treatments such as lotions for ectopic application onto skin, or as orally administered drugs.MethodsDifferent concentrations of DMSO-dissolved remnants of crude methanol Rhododendron leaf extracts were incubated for 24 h with cultured epidermal keratinocytes (human HaCaT cell line) and epithelial cells of the intestinal mucosa (rat IEC6 cell line) and tested for their cytotoxic potential. In particular, the cytotoxic potencies of the compounds contained in antimicrobial Rhododendron leaf extracts were assessed by quantifying their effects on (i) plasma membrane integrity, (ii) cell viability and proliferation rates, (iii) cellular metabolism, (iv) cytoskeletal architecture, and (v) determining initiation of cell death pathways by morphological and biochemical means.ResultsExtracts of almost all Rhododendron species, when applied at 500 μg/mL, were potent in negatively affecting both keratinocytes and intestine epithelial cells, except material from R. hippophaeoides var. hippophaeoides. Extracts of R. minus and R. racemosum were non-toxic towards both mammalian cell types when used at 50 μg/mL, which was equivalent to their minimal inhibitory concentration against bacteria. At this concentration, leaf extracts from three other highly potent antimicrobial Rhododendron species proved non-cytotoxic against one or the other mammalian cell type: Extracts of R. ferrugineum were non-toxic towards IEC6 cells, and extracts of R. rubiginosum as well as R. concinnum did not affect HaCaT cells. In general, keratinocytes proved more resistant than intestine epithelial cells against the treatment with compounds contained in Rhododendron leaf extracts.ConclusionsWe conclude that leaf extracts from highly potent antimicrobial R. minus and R. racemosum are safe to use at 50 μg/mL in 24-h incubations with HaCaT keratinocytes and IEC6 intestine epithelial cells in monolayer cultures. Extracts from R. rubiginosum as well as R. concinnum or R. ferrugineum are applicable to either keratinocytes or intestinal epithelial cells, respectively. Beyond the scope of the current study, further experiments are required to identify the specific compounds contained in those Rhododendron leaf extracts that exert antimicrobial activity while being non-cytotoxic when applied onto human skin or gastrointestinal tract mucosa. Thus, this study supports the notion that detailed phytochemical profiling and compound identification is needed for characterization of the leaf extracts from specific Rhododendron species in order to exploit their components as supplementary agents in antimicrobial phyto-medical treatments.Electronic supplementary mate...

Bioactivity in Rhododendron: A Systemic Analysis of Antimicrobial and Cytotoxic Activities and Their Phylogenetic and Phytochemical Origins

“…To this end, additionally the cytotoxicity toward mammalian cell lines of numerous Rhododendron crude leaf extracts has been investigated. In one of our previous studies, it was shown that the Rhododendron 's cytotoxicity toward epidermal keratinocytes and intestine epithelial cells can be assessed by testing for their effects on metabolic activities and proliferation rates (MTT assay) of cultured mammalian cells in vitro (Rezk et al, 2015a). The MTT assay thus provides a means of rapid high-throughput screening with good approximation potential in predicting cytotoxic effects of Rhododendron -derived extracts using an easily performed and well-standardized cell viability assay (Karar et al, 2016).…”

Propuesta para seleccionar aceites esenciales de plantas de Colombia para investigación con base en su citotoxicidad

“…No se encontraron trabajos similares sobre citotoxicidad de AE luego de una revisión exhaustiva de sistema de búsqueda de artículos científicos. Rezk et al (21) compararon la citotoxicidad del extracto de especies del género Rhododendron, analizando cada muestra simultáneamente en dos líneas celulares mediante ensayos que miden distinto parámetro de muerte celular. Usando un abordaje distinto de jerarquización, los autores lograron identificar la especie más promisoria para incluir en futuros estudios sobre antimicrobianos.…”

“…La variación de citotoxicidad dependiendo del tipo de línea celular ha sido demostrada en otros trabajos (13,21,28). La actividad varió también con respecto al tratamiento, siendo mayor después de la proliferación, que es resultado de esperar, ya que a las 24 h la división celular disminuye porque la monocapa celular ha alcanzado 75 -80%.…”

Glycemic Regulation and Cytotoxic Characteristics of the Ethyl Acetate Fraction from <em>Passiflora cincinnata</em> Mast Leaves

“…As a result, [46] suggested the use of natural glycoside inhibitors in the control of postprandial glycemia. [47] reported that due to the presence of phenols and flavonoids, several medicinal plants are still the most promising sources for the discovery of α-amylase inhibitor, receiving considerable attention from the pharmaceutical industry. The fact is that these medicines are quite relevant for those people who have just been diagnosed with type 2 diabetes and who have blood glucose levels only slightly above the level considered serious for diabetes.…”

“…On the other hand, F.MET and F.ACT presented significant (p < 0.05) inhibitory potential for α-amylase, whereas F.ACT showed its best activity in relation to the other samples at 20 μg.mL -1 , with 89.16% of inhibition (table 2) and the lowest IC50, which was half of the value observed for control acarbose. A study conducted by [47] demonstrated that ethanol and aqueous extracts from other Passiflora species have α-amylase inhibitory activity at a dose-dependent concentration. In that study, the highest concentration of the ethanol and aqueous root extracts (100 μg.mL -1 ) showed inhibitions of 80.3% and 83.3%, respectively, which were lower than observed for P. cincinnata F.ACT in the present study.…”