A strategy based on fingerprinting and chemometrics for the detection of regulated plants in plant food supplements from the Belgian market: Two case studies

Highlights

• A first rapid screening model for 5 regulated plants was build using infrared spectroscopy.

• Screening results were confirmed using binary models for each plant based on chromatographic fingerprints.

• This two-step approach was applied in a market study.

• 21 samples of 69 contained one of the targeted plants.

Abstract

The sale and consumption of plant food supplements is increasing, especially in the western world. A lot of these supplements can be bought through internet, where a lot of illegal trade is going on. Every year seized dietary supplements are send to laboratories in order to screen for the presence of chemical adulterants or illegally added active pharmaceutical ingredients, though also herbal adulteration occurs and is given less attention.

In this paper a two-step approach is presented based on fingerprints recorded by both infrared spectroscopy as liquid chromatography with UV-detection for the screening of five regulated plants used in respectively dietary supplements for slimming and potency enhancement. Both types of fingerprints are combined with chemometric techniques in order to obtain classification models. A first classification model is calculated based on the infrared data and gives a first idea about the plant suspected to be present. This suspicion is then confirmed based on binary classification models calculated with the chromatographic data obtained for the suspected plant. In general, good classification models were obtained for each of the targeted plants.

The approach was applied in a small market study comprising 35 dietary supplements for slimming and 34 for male potency enhancement. In total 21 samples were found to contain one of the five targeted plants.

Introduction

The popularity and therefore the consumption of plant food supplements is an increasing trend in the western world. This trend can be explained by the general trend of returning to natural and traditional products, which is exhaustively promoted by marketing campaigns, but also by the evolution towards self-medication, the concerns about adverse effects and more general the questioning of allopathic medicines and the misperception that “natural” and “herbal” are synonyms for “safe”. The latter are an immediate result of the previous mentioned marketing campaigns around these kind of products [1].

The increasing popularity of these plant food supplements led to the development of a market offering a wide range of different products and representing high profits. The latter makes these products vulnerable for fraud and adulteration, especially since they can also be purchased via internet, an interesting platform for the trade of falsified, suspicious or illegal products [[2], [3], [4], [5], [6], [7]]. Two issues, resulting in possible health threats, may occur with plant food supplements, especially when they are purchased from an irregular source: (a) a first problem can be that the supplement does not contain the plant or herb mentioned on the ingredient list. For this there are two possibilities: (1) the first is falsification or fraud. In this case the plant food supplements contain some common dried plants instead of the medicinal plants in order to create a cheap counterfeit product. (2) the second possibility is confounding. The therapeutic properties are often related to one specific plant species, while other related species have less or no therapeutic activities or have other, possible toxic properties. This confounding can be either deliberately (fraud, the other species is cheaper) or accidently due to confusion with e.g. nomenclature used in traditional Chinese or Aryuvedic medicine. (b) The second problem is adulteration. Also here two different possibilities occur: chemical adulteration and herbal adulteration. In the first case the supplement contains a chemical drug or active pharmaceutical ingredient. The presence is not claimed on the packaging and therefore the consumers do not know they are in fact taking a medicine. This can represent a serious health risk for the consumers since these products can lead to adverse and toxic effects as well as interference with other medical treatments. In the second case the product contains active plants or herbs which are not claimed on the packaging or are regulated or toxic.

This paper tries to tackle the latter problem of herbal adulteration by proposing a strategy to screen plant food supplements for toxic or regulated plants. Following the European directive plant food supplements need a market authorization of one of the national authorities and the market authorization holder should demonstrate the safety and efficacy of the product [8]. In Belgium the plant food supplements fall under a Royal Decree issued in 1997 and amended in 2012. The text contains three lists: the first list contains all toxic herbs, forbidden in herbal supplements. The second list contains all edible mushrooms and list three describes all plants, allowed in plant food supplements when notified to the Federal Public Service of Public Health [9].

The present paper deals with the problem of the presence of potential toxic and regulated plants in plant food supplements. Polymeric chain reaction analysis (PCR) is the golden standard for the detection and identification of a specific plant [[10], [11], [12]]. This technique is therefore very valuable, especially in the detection of fraud, i.e. does the plant food supplement contains the plant claimed or not. Also in the targeted analysis for a specific plant in a plant food supplement PCR is probably the best choice. On the other hand, in the case of adulteration or the necessity of screening for a series of plants PCR becomes more tedious. The more laboratories charged with the analysis of suspicious plant food supplements are often chemical laboratories with no expertise or access to PCR. Therefore, these analyses should be outsourced, representing a high cost for the laboratories involved.

In previous research our group demonstrated that it is possible to detect toxic and regulated plants in plant food supplements using a fingerprint approach based on infrared spectroscopy [13] and chromatography [[14], [15], [16]].

Chromatographic fingerprinting is a well-accepted technique in pharmacognosy and the quality control of herbs and plants [17], though it was only sporadically used for the detection of plants in herbal mixtures like plant food supplements. Also chromatographic fingerprints are often developed for each plant specifically, leading to the fact that when you need to screen for several plants it is necessary to record several fingerprints with different chromatographic methods. Therefore, a kind of prescreening would be necessary in order to focus the fingerprinting analysis in chromatography to one plant. As shown before infrared spectroscopy can be useful in this context. Based on fingerprints recorded in the Mid-IR region and chemometric modeling it is possible to distinguish between plant food supplements containing different targeted plants [13].

In this paper, previous research with Mid-IR and chromatography in this domain, is combined to one strategy in order to screen for and confirm the presence of five regulated plants in plant food supplements. The strategy combines the information obtained from chemometric modeling of the Mid-IR spectra with chromatographic fingerprinting. Also in the latter, chemometric modeling was applied. The strategy was used to perform a market surveillance study on 69 plant food supplements, from which 35 claimed weight loss properties and 34 enhancement of male potency.