Phytochemical Profiling and Quality Control of Terminalia sericea Burch. ex DC. Using HPTLC Metabolomics

Nduvho Mulaudzi,Sandra Combrinck,Weiyang Chen,Sidonie Y Tankeu,Ilze Vermaak,Alvaro M Viljoen,Chinedu P Anokwuru

doi:10.3390/molecules26020432

Abstract

Terminalia sericea is used throughout Africa for the treatment of a variety of conditions and has been identified as a potential commercial plant. The study was aimed at establishing a high-performance thin layer chromatography (HPTLC) chemical fingerprint for T. sericea root bark as a reference for quality control and exploring chemical variation within the species using HPTLC metabo3lomics. Forty-two root bark samples were collected from ten populations in South Africa and extracted with dichloromethane: methanol (1:1). An HPTLC method was optimized to resolve the major compounds from other sample components. Dichloromethane: ethyl acetate: methanol: formic acid (90:10:30:1) was used as the developing solvent and the plates were visualized using 10% sulfuric acid in methanol as derivatizing agent. The concentrations of three major bioactive compounds, sericic acid, sericoside and resveratrol-3-O-β-rutinoside, in the extracts were determined using a validated ultra-performance liquid chromatography-photodiode array (UPLC-PDA) detection method. The rTLC software (written in the R-programming language) was used to select the most informative retardation factor (Rf) ranges from the images of the analysed sample extracts. Further chemometric models, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were constructed using the web-based high throughput metabolomic software. The rTLC chemometric models were compared with the models previously obtained from ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). A characteristic fingerprint containing clear bands for the three bioactive compounds was established. All three bioactive compounds were present in all the samples, although their corresponding band intensities varied. The intensities correlated with the UPLC-PDA results, in that samples containing a high concentration of a particular compound, displayed a more intense band. Chemometric analysis using HCA revealed two chemotypes, and the subsequent construction of a loadings plot indicated that sericic acid and sericoside were responsible for the chemotypic variation; with sericoside concentrated in Chemotype 1, while sericic acid was more abundant in Chemotype 2. A characteristic chemical fingerprint with clearly distinguishable features was established for T. sericea root bark that can be used for species authentication, and to select samples with high concentrations of a particular marker compound(s). Different chemotypes, potentially differing in their therapeutic potency towards a particular target, could be distinguished. The models revealed the three analytes as biomarkers, corresponding to results reported for UPLC-MS profiling and thereby indicating that HPTLC is a suitable technique for the quality control of T. sericea root bark.

Highlights

It has been estimated that southern Africa is home to 30,000 species of Higher Plants, of which roughly 24,000 are indigenous to South Africa [1]
High-performance thin layer chromatography (HPTLC) is a readily available semi-automated technique used for rapid-throughput screening of samples to authenticate herbal products and to differentiate between related herbal species [7]
(1:1) for 10 min using an ultrasonic bath (ULTRA-SONIC, LIBMB, Labcon, Krugersdorp, South Africa), where after the extract was filtered through a 0.45 μm nylon syringe filter (Acrosdisc®, Pall, New York, NY, USA) prior and transferred to individual autosampler vials for high-performance TLC (HPTLC) analysis

Summary

Introduction

It has been estimated that southern Africa is home to 30,000 species of Higher Plants, of which roughly 24,000 are indigenous to South Africa [1]. Marker compounds that can be used for species verification and to evaluate the chemical consistency of raw materials and products, have not been identified for the majority of plant species with commercial potential [3]. A variety of chromatographic fingerprinting techniques are available for the QC of herbal products. These include highly sophisticated techniques such as gas chromatography (GC) with mass spectrometry (MS) and/or other detection systems, and high-performance- (HPLC) or ultra-performance liquid chromatography (UPLC) coupled with MS or other detection systems [4]. High-performance thin layer chromatography (HPTLC) is a readily available semi-automated technique used for rapid-throughput screening of samples to authenticate herbal products and to differentiate between related herbal species [7]

Methods

Results

Conclusion