Assessing radical scavenging capacity of Sempervivum tectorum L. leaf extracts: An integrated high-performance thin-layer chromatography/in silico/chemometrics approach

High-Performance Thin-Layer Chromatography (HPTLC)-radical scavenging capacity (RSC) assays are standard techniques for the separation and identification of antioxidants from complex mixtures. HPTLC coupled with DPPH & BULL; visualization of chromatograms allows for the detection of individual antioxidants. However, other HPTLC-RSC assays that recognize compounds exhibiting different mechanisms of radicalscavenging activity are rarely reported. In this study, we developed an integrated approach that combines five HPTLC-RSC assays, principal component analysis (PCA) and quantum chemical calculations to assess the antioxidant capacity of Sempervivum tectorum L. leaf extracts. Two HPTLC assays - potassium hexacyanoferrate(III) total reducing power assay (TRP) and total antioxidant capacity by phosphomolybdenum method (TAC) - were developed for the first time. The method supports a more in-depth study of the RSC of natural products, as it compares the radical scavenging fingerprints of S. tectorum leaf extracts and recognizes differences in their individual bioactive constituents. Kaempferol, kaempferol 3- O -glucoside, quercetin 3- O -glucoside, caffeic acid, and gallic acid were identified as the compounds that discriminate HPTLC-RSC assays according to their mechanism of action and capture the similarities between 20 S. tectorum samples. Additionally, DFT calculations on M06-2X/6-31 + G (d,p) level were applied to map thermodynamic feasibility of hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms of the identified compounds. Based on experimental and theoretical results, a combination of HPTLC-ABTS and HPTLC-TAC assays were proposed as the optimal method for mapping the antioxidants from S. tectorum . This study represents a step forward in identifying and quantifying individual antioxidants from complex food and natural product matrices in a more rational manner.& COPY; 2023 Elsevier B.V. All rights reserved.

Automated summary

HPTLC-RSC assays are standard techniques for identifying antioxidants. This study developed an integrated approach combining HPTLC-RSC assays, PCA, and quantum chemical calculations to evaluate the antioxidant capacity of S. tectorum leaf extracts. The optimal method proposed was HPTLC-ABTS and HPTLC-TAC assays.