Innovative methods based on the fused-core technology for the HPLC analysis of natural products

Plant extracts are composed of a complex mixture of different phytochemicals (plant secondary metabolites). Frequently, these constituents work “synergistically” and cannot be separated into active parts. Consequently, it is necessary to define all the phytochemical constituents of plant extracts to understand the bioactivity and possible adverse effects of active compounds, and to enhance product quality control. Due to the complex composition of plant extracts, separation methods are highly recommended in phytochemical analysis. HPLC is the most frequently used technique for both quali- and quantitative analysis of natural compounds. However, the HPLC analysis of plant extracts usually requires a long analysis time on conventional fully porous stationary phases. The most recently reported strategy for improving the chromatographic performance in the analysis of complex matrices is based on the fused-core technology (also known as core-shell technology). In this ambit, this work provides several examples of the application of reversed-phase fused-core stationary phases for the metabolite profiling/fingerprinting of natural products widely used in phytotherapy, including propolis (phenolic acids and flavonoids), Humulus lupulus L. (prenylflavonoids and prenylphloroglucinols) and Echinacea pallida (Nutt.) Nutt. (polyacetylenes and polyenes). An additional example related to the phytochemical analysis of steviol glycosides in Stevia rebaudiana Bertoni is also provided. In particular, these examples demonstrate that the fused-core columns offer good chromatographic performance, such as narrow peaks, high resolution and a short analysis time.