A Fast and Reliable UHPLC-MS/MS-Based Method for Screening Selected Pharmacologically Significant Natural Plant Indole Alkaloids.

Danuše Tarkowská

doi:10.3390/molecules25143274

Abstract

Many substances of secondary plant metabolism have often attracted the attention of scientists and the public because they have certain beneficial effects on human health, although the reason for their biosynthesis in the plant remains unclear. This is also the case for alkaloids. More than 200 years have passed since the discovery of the first alkaloid (morphine), and several thousand substances of this character have been isolated since then. Most often, alkaloid-rich plants are part of folk medicine with centuries-old traditions. What is particularly important to monitor for these herbal products is the spectrum and concentrations of the present active substances, which decide whether the product has a beneficial or toxic effect on human health. In this work, we present a fast, reliable, and robust method for the extraction, preconcentration, and determination of four selected alkaloids with an indole skeleton, i.e., harmine, harmaline, yohimbine, and ajmalicine, by ultra-high performance liquid chromatography coupled with tandem mass spectrometry. The applicability of the method was demonstrated for tobacco and Tribulus terrestris plant tissue, the seeds of Peganum harmala, and extract from the bark of the African tree Pausinystalia johimbe.

Highlights

Alkaloids are a well-known and important group of natural substances
The extraction and purification procedure was developed with respect to both the relatively hydrophobic and the alkaline character of all studied compounds, which was demonstrated by their dissociation constant pKa ranging from 6.31 to 9.55 [16]
This work focused on the development of a new microscale method for the extraction, preconcentration, and determination of harmine, harmaline, ajmalicine, and yohimbine, which are indole alkaloids with sympatholytic activity derived from the tryptophan amino acid in plant tissue

Summary

Introduction

Alkaloids are a well-known and important group of natural substances. The name “alkaloid” is derived from the alkaline nature of most of these substances, thanks to which it forms salts with acids.Most alkaloids occur in flowering plants as products of secondary metabolism, mainly in the form of salts with organic acids (acetic, oxalic, citric, lactic, tartaric), rarely in free form [1]. Alkaloids are a well-known and important group of natural substances. The name “alkaloid” is derived from the alkaline nature of most of these substances, thanks to which it forms salts with acids. Most alkaloids occur in flowering plants as products of secondary metabolism, mainly in the form of salts with organic acids (acetic, oxalic, citric, lactic, tartaric), rarely in free form [1]. Alkaloids are mostly derived from amino acids, namely, ornithine, lysine, phenylalanine, tyrosine, tryptophan, and histidine. The subject of this article is indole alkaloids (IAs) in particular. This group of alkaloids have a common structural feature, the indole skeleton, which is biosynthetically derived from amino acid tryptophan (Trp; Figure 1). According to the structure of Molecules 2020, 25, 3274; doi:10.3390/molecules25143274 www.mdpi.com/journal/molecules

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