NMR and Chemometric Analysis of Verbascoside and Isoverbascoside Produced in Tecoma stans In Vitro Cultures

Abstract

Verbascoside and isoverbascoside are phenylethanoid glycosides with reported biological activities such as neuroprotection, hepatoprotection, anti-inflammatory, antimicrobial, anticancer, and antioxidant properties. These compounds are constitutively present in roots, stems, leaves, and flowers of various plant species, including Tecoma stans. In Mexico, this plant is traditionally used as a safe and effective herbal treatment for chronic diseases and its complications including diabetes and renal and hepatic disorders. The potential pharmacological applications of verbascoside and isoverbascoside have conducted efforts to produce these compounds in cell and plant tissue cultures. In this study, T. stans root and plantlet in vitro cultures were established as potential sources of verbascoside and isoverbascoside, and NMR was used as primary analytical tool. As a first step, proton and bidimensional NMR analysis confirmed the presence of verbascoside and isoverbascoside in T. stans in vitro culture extracts. Subsequently, their contents were quantified by means of quantitative NMR (qNMR) based on the external standard PULCON method. Furthermore, 1H-NMR spectral data were used to develop a descriptive PLS-DA model, which confirms the qNMR results. This model indicated that differences in the amounts and proportions of verbascoside and isoverbascoside produced by roots and plantlets are the primary factors in distinguishing these samples. These results demonstrate the capability of T. stans in vitro systems as biotechnological tools for obtaining phenylethanoids with high pharmacological potential and confirm the broad applicability of NMR as an analytical platform. However, additional experiments are necessary to improve the phenylethanoids glucoside yields and support the validation of the qNMR method.