Quality variation of maidong (Ophiopogon japonicus and Liriope spicata) - A HPTLC-based approach.

The tuberous roots of Ophiopogon japonicus and Liriope spicata are used for the same therapeutic purpose in traditional Chinese medicine and are collectively referred to as maidong medicine. Interestingly, it was observed that the price of tuberous roots varies depending on their location on the plant, and fibrous roots are usually discarded post-harvest. Mislabeling might be of concern due to similarities in morphological features between the two species. Moreover, paclobutrazol has been observed to be heavily applied during the production, and therefore might be of health concern. Overall, maidong might suffer from quality inconsistencies while its metabolomic complexity is influenced by growing region and cultivation practices, botanical species, and plant parts. To address these challenges, this study employed High-Performance Thin Layer Chromatography (HPTLC) approach, in which sample preparation and derivatization procedure were optimized to enable to capture more detailed and comprehensive metabolomic fingerprints. By integrating with rTLC algorithm and Multivariate Data Analysis (MVDA), an improved quality assessment was achieved. Samples were collected from four production regions and supplemented with commercial products from markets. The optimized HPTLC analysis recognized species- and region-specific metabolomic patterns of maidong, uncovering a 4% of mislabelled cases. Moreover, findings highlight the underexplored therapeutic potential of fibrous roots, and comparable therapeutic efficacy between different root types. Additionally, complemented by Liquid Chromatography-Mass Spectrometry (LC-MS) for paclobutrazol residue evaluation, 24.66% of the commercial maidong samples surpassed maximum residue limits of paclobutrazol, raising safety concerns. This research represents a significant analytical advancement, offering a robust, cost-effective, and comprehensive method for maidong quality control, and paving the way for more strict residue regulation and updates to herbal pharmacopoeias and monographs.

Comprehensive high-performance thin-layer chromatography analysis of Monteverdia ilicifolia leaf and its adulterants.

The leaves of Monteverdia ilicifolia (syn. Maytenus ilicifolia) are widely used in traditional South American medicine to treat gastrointestinal problems such as gastritis and ulcers. Several herbal products containing the leaves of M. ilicifolia can be found in the market. However, other species with similar leaf morphology are confounding materials, e.g. Monteverdia aquifolia (Celastraceae), Citronella gongonha (Cardiopteridaceae), Jodina rhombifolia (Santalaceae), Sorocea bonplandii (Moraceae) and Zollernia ilicifolia (Fabaceae). This study aimed to identify M. ilicifolia and distinguish it from its potential adulterants using high-performance thin-layer chromatography (HPTLC) technique. Comprehensive HPTLC analysis revealed specific fingerprints that can be used to assess the minimum content of epicatechin and the quality of commercial espinheira-santa samples. The results of the study demonstrated that the HPTLC method is capable of detecting adulterations and distinguishing M. ilicifolia from all confounding materials in commercial products available on the market, showing that most of the products are of poor quality due to adulterations.

Investigation of market herbal products regulated under different categories: How can HPTLC help to detect quality problems?

Background: Herbal products regulated under different categories were found to be of different quality. This has been demonstrated by the increasing number of reports on the quality of herbal products in the scientific literature. Proper identification is an effective way to address this concerning issue early on in a products' manufacturing process. Objectives: To assess the quality of milk thistle, coneflower and black cohosh herbal drugs, preparations and products commercialized under different regulatory categories, and to illustrate the usefulness of HPTLC as a tool for evaluating quality. Methods: HPTLC methods were adapted from the European Pharmacopeia's monographs for milk thistle fruits, black cohosh and purple coneflower. Additional detection modes beyond those described in the monographs were employed, and the entire HPTLC fingerprints were used for examination of identity and purity of the investigated samples. Results: All products regulated as Traditional Herbal Medicinal Products were shown to be of high quality: their fingerprints were consistent and without unexpected zones. A significant number of food supplements show quality issues (mainly adulterations): 52.4% of milk thistle, 33.3% of coneflower, and 45.5% of black cohosh products. The same was observed in 66.6% of black cohosh herbal drugs and preparations.

Applicability of the Universal Mixture for describing system suitability and quality of analytical data in routine normal phase High Performance Thin Layer Chromatography methods.

The Universal HPTLC Mixture (UHM) consists of eight substances (guanosine, sulisobenzone, thymidine, paracetamol, phthalimide, 9-hydroxyfluorene, thioxanthen-9-one, and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol) and yields separated zones over the whole RF range for a multitude of developing solvents. Therefore, it could be used in a generic system suitability test (SST) as well as for the verification of quality of HPTLC data. In this work, changes caused by ±10% variation of the volume fractions of the developing solvent components were tested on three developing solvents, to investigate the RF shifts of the UHM zones in comparison to established SSTs and results described for test samples in selected pharmacopeia monographs for identification of herbal drugs. Additionally, one of the developing solvents was investigated with different stationary phases. The components of the UHM showed similar prediction intervals as the substances of established SSTs and specific markers. The UHM could, therefore, be considered for use in an alternative SST. Because it covers the whole RF range, the UHM can detect changes in developing solvent gradients or saturation effects, whereas many established SSTs generally describe only a limited RF range. The use of the UHM can help facilitate automation of HPTLC. Furthermore, it can potentially be used for correlating RF shifts across HPTLC plates. The circumstances, under which this is possible, are discussed.

Development of the first universal mixture for use in system suitability tests for High-Performance Thin Layer Chromatography.

The use of chromatographic methods in routine analysis includes System Suitability Tests (SST). This paper presents a novel approach to SST in HPTLC, which allows qualification of the entire RF range of an HPTLC plate independently of the samples. It is based on the Universal HPTLC mix (UHM), a pre-defined mixture of eight reference substances: guanosine, sulisobenzone, thymidine, paracetamol, phthalimide, 9-hydroxyfluorene, thioxanthen-9-one, and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, selected to cover a broad range of polarities and functional groups. The chromatographic behavior of the UHM was evaluated for 20 different mobile phases on Silica gel 60 F254. At least three constituents were baseline separated. In a collaborative trial with four laboratories the reproducibility of RF values for three representative mobile phases, was found to be within a confidence interval of 0.040 RF units. The response characteristics of the UHM were assessed with respect to changes in chromatographic conditions, such as variation of the relative humidity, improperly employed saturation, or mistakes in the preparation of the mobile phase. Based on the RF values of the individual constituents significant responses were found for most changes. This qualifies the UHM for use in SST.

Comprehensive HPTLC fingerprinting as a tool for a simplified analysis of purity of ginkgo products.

ETHNOPHARMACOLOGICAL RELEVANCE: Herbal medicinal products based on ginkgo leaf refined dry extract (GBE) are an European development from the Eastern Asia traditionally used species Ginkgo biloba L. Nowadays, ginkgo products have increased the presence in the market, mainly as dietary supplements. Its adulteration with rutin and quercetin or herbal extracts rich in these compounds is a common practice. Tests featuring assays and detection of adulterants need to be performed on top of other existent methods (e.g. identification test). This may increase the costs of evaluating the quality of ginkgo products. AIM OF THE STUDY: To prove that comprehensive HPTLC fingerprinting can provide information beyond identification of ginkgo products, avoiding additional chromatographic tests for detection of adulterations. MATERIALS AND METHODS: The information contained in the fingerprint obtained by HPTLC analysis of flavonoids was used for identification and for detection of adulterants, as well as to verify the limits of rutin and quercetin, which are normally determined by HPLC and used for detection of adulterants. For this purpose, peak profiles were generated from HPTLC chromatogram images. USP-HPLC methods were used for quantification of total flavonoids and testing the limits of rutin and quercetin. HPLC data were used to support the validity of the HPTLC method. An additional reversed phase HPTLC method was developed as a possible confirmatory method for the quercetin limit test. RESULTS: The proposed HPTLC method uses a particular sequence of detections, resulting in a number of images, which are later interpreted in a certain order. It is able to identify ginkgo products, to detect adulterants (rutin, quercetin, sophora fruit and flower bud, and buckwheat), and, using peak profiles generated from the chromatogram images prior to and after derivatisation, to evaluate the limits of rutin and quercetin. Forty-eight out of fifty-nine ginkgo dietary supplements analysed contained one or more adulterants. Furthermore, results of the HPTLC and HPLC limit tests for rutin and quercetin were in agreement in 98% of the cases. Finally, a decision tree showing the sequence of interpretation of the fingerprints obtained with the different detections after a single HPTLC analysis is included to help the analyst to evaluate whether samples have the correct identity and whether they contain or not adulterants. CONCLUSION: A single HPTLC analysis is able to provide information on identity and purity of the products. This simplifies the analytical workflow and reduces the number of analyses prescribed in the USP powdered ginkgo extract monograph.

HPTLC Screening of Weight Loss Products for Deliberately Added Undeclared Synthetic Drugs.

Background: The proposed HPTLC method combines features of the existing methods for (1) the detection of sibutramine and (2) for the detection of phosphodiesterase type 5 inhibitors and analogs. Objective: The method permits effective screening for the presence of nine adulterants in finished products, including tablets, capsules, and "instant coffee" powders. Methods: All products were prepared for analysis using the same simple procedure: ultrasound-assisted extraction in methanol for 30 min followed by centrifugation or filtration. Results: The retardation factor (RF) values of individual zones afford preliminary identification of potential adulterants. Scanning densitometry enables comparison of recorded UV spectra with those of known standard compounds and provides further structural information. Conclusions: The method was successfully applied to 12 commercial products. Of those, nine products tested positive for at least one undeclared component.

Product authenticity versus globalisation-The Tulsi case.

Using the Indian medicinal plant Tulsi (Holy Basil) as a case study, we have tested to what extent the discrepancy between vernacular and scientific nomenclature can be resolved, whether the presumed chemical diversity underlying the medicinal use of Tulsi has a genetic component, and whether it is possible to detect this genetic component using genetic barcoding markers. Based on four plastidic markers, we can define several haplotypes within Ocimum that are consistent across these markers. Haplotype II is congruent with O. tenuiflorum, while haplotype I extends over several members of the genus and cannot be resolved into genetically separate subclades. The vernacular subdivision of Tulsi into three types (Rama, Krishna, Vana) can only be partially linked with genetic differences-whereby Rama and Krishna Tulsi can be assigned to O. tenuiflorum, while Vana Tulsi belongs to haplotype I. This genetic difference is mirrored by differences in the profiles of secondary compounds. While developmental state and light quality modulate the amplitude to which the chemical profile is expressed, the profile itself seems to be linked with genetic differences. We finally develop an authentication assay that makes use of a characteristic single nucleotide polymorphism in one of the barcoding markers, establishing a differential restriction pattern that can be used to discriminate Vana Tulsi.

HPTLC fingerprint profile analysis of cocoa proanthocyanidins depending on origin and genotype.

Cocoa beans are rich in bioactive phytochemicals such as alkaloids, anthocyanins, as well as monomeric and oligomeric flavan-3-ols. A high performance thin layer chromatography (HPTLC) method was developed for a fast analysis of a fingerprint of bioactive compounds present in cocoa beans depending on genotype and origin. Evaluation was performed using HPTLC followed by densitometry. The best separation for a fingerprint consisting of eight phenolic compounds as markers was achieved on silica gel 60 F254 HPTLC plates with a solvent mixture of ethyl formate, formic acid, water, toluene 30/4/3/1.5 (v/v/v/v). Staining with Fast Blue Salt B enabled visualization and quantitative evaluation. Compounds of interest were confirmed by eluting zones using a TLC-MS interface. LODs were ≤ 100ng/zone for all compounds. The fingerprints obtained are useful for quality control of cocoa beans allowing their differentiation according to cocoa or chocolate sorts, varieties, and origins.

Comprehensive HPTLC Fingerprinting for Quality Control of an Herbal Drug - The Case of Angelica gigas Root.

The quality of herbal drugs is usually controlled using several tests recommended in a monograph. HPTLC is the method of choice for identification in many pharmacopoeias. If combined with a suitable reference material for comparison, HPTLC can provide information beyond identification and thus may simplify quality control. This paper describes, as a proof of concept, how HPTLC can be applied to define specifications for an herbal reference material and to control the quality of an herbal drug according to these specifications. Based on multiple batches of cultivated Angelica gigas root, a specific HPTLC method for identification was optimized. This method can distinguish 27 related species. It also can detect the presence of mixtures of A. gigas with two other Angelica species traded as "Dang gui" and is suitable as well for quantitative assessment of samples in a test for minimum content of the sum of decursin and decursinol angelate. The new concept of "comprehensive HPTLC fingerprinting" is proposed: HPTLC fingerprints (images), which are used for identification, are converted into peak profiles and the intensities of selected zones are quantitatively compared to those of the corresponding zones of the reference material. Following a collaborative trial involving three laboratories in three countries, the method was applied to check the quality of further candidates for establishing an appropriate reference material. In conclusion, this case demonstrates that a single HPTLC analysis can provide information about identity, purity, and minimum content of markers of an herbal drug.

St John's wort (Hypericum perforatum) products - an assessment of their authenticity and quality.

BACKGROUND: St John's wort products (Hypericum perforatum L.) are widely available for sale in many countries including the UK via the internet. In the UK, these products are required to hold either a marketing authorisation or Traditional herbal registration (THR) to be sold legally. The THR and other regulatory schemes help to ensure product safety and quality providing an example of best practice but there is a risk if both regulated and un-regulated products continue to be available to consumers. AIMS: The project is embedded in a larger study aiming to investigate the quality of different herbal medicinal products along diverse value chains. Here we focus on a comparison of the quality of the finished products and assess phytochemical variation between registered products (THRs) and products obtained from the market without any registration. METHODS: 47 commercial products (granulated powders and extracts) were sourced from different suppliers. We analysed these samples using high performance thin layer chromatography (HPTLC) and 1H NMR spectroscopy coupled with multi-variate analysis software following a method previously developed by our group. RESULTS: The consistency of the products varies significantly. Adulteration of the products (36%), possibly with other Hypericum species obtained from China or use of chemically distinct H. perforatum cultivars or chemotypes, and adulteration of the products (19%) with food dyes (tartrazine, amaranth, brilliant blue, sunset yellow) were the principle findings of this study. CONCLUSIONS: There is significant compositional variation among commercial finished products and two main causative quality problems were identified as adulteration by incorrect species or adulteration with food dyes. Generally, food supplements and unlicensed products were found to be of poorer quality than the regulated ones including THRs.

Quality Variation of Goji (Fruits of Lycium spp.) in China: A Comparative Morphological and Metabolomic Analysis.

Goji (fruits of Lycium barbarum L. and L. chinense Mill.) has been used in China as food and medicine for millennia, and globally has been consumed increasingly as a healthy food. Ningxia, with a semi-arid climate, always had the reputation of producing best goji quality (daodi area). Recently, the increasing market demand pushed the cultivation into new regions with different climates. We therefore ask: How does goji quality differ among production areas of various climatic regions? Historical records are used to trace the spread of goji production in China over time. Quality measurements of 51 samples were correlated with the four main production areas in China: monsoon (Hebei), semi-arid (Ningxia, Gansu, and Inner Mongolia), plateau (Qinghai) and arid regions (Xinjiang). We include morphological characteristics, sugar and polysaccharide content, antioxidant activity, and metabolomic profiling to compare goji among climatic regions. Goji cultivation probably began in the East (Hebei) of China around 100 CE and later shifted westward to the semi-arid regions. Goji from monsoon, plateau and arid regions differ according to its fruit morphology, whereas semi-arid goji cannot be separated from the other regions. L. chinense fruits, which are exclusively cultivated in Hebei (monsoon), are significantly lighter, smaller and brighter in color, while the heaviest and largest fruits (L. barbarum) stem from the plateau. The metabolomic profiling separates the two species but not the regions of cultivation. Lycium chinense and samples from the semi-arid regions have significantly (p < 0.01) lower sugar contents and L. chinense shows the highest antioxidant activity. Our results do not justify superiority of a specific production area over other areas. Instead it will be essential to distinguish goji from different regions based on the specific morphological and chemical traits with the aim to understand what its intended uses are.

Ethnopharmacological and Chemical Characterization of Salvia Species Used in Valencian Traditional Herbal Preparations.

In Valencia Region (Spain), some wild and cultivated sages are used for medicinal purposes. Among them, Salvia officinalis subsp. lavandulifolia (SL) is widely employed and known for production of Spanish sage oil and herbal products. Nevertheless, it shares the market with S. blancoana subsp. mariolensis (SB) and, to a lesser extent, with their hybrid S. x hegelmaieri (SH). The knowledge on these two species is far low and confusion between them is possible. The aim of the present paper is to improve the ethnopharmacological, morphological and chemical knowledge of these sages, and to contribute to setting up quality specifications for improving identification and distinction from other Salvia species, such as, S. officinalis subsp. officinalis, S. x auriculata and S. microphylla var. microphylla. Samples were collected in Valencia Region and surrounding mountain areas during the ethnopharmacological field work. Twenty-nine medicinal uses were reported for SL, 13 of them being also recorded for SB. Of particular interest is a homemade liquor, used as digestive and known as "salvieta," which is mainly prepared with SB. The macro- and microscopic characters are insufficient for identification of cut, crushed or powdered material. The study of the essential oil and a HPTLC (High Performance Thin Layer Chromatography) fingerprint of their extracts could help to distinguish SB from the other sages. The essential oil from dried aerial parts of SB (content: 1.8-4.5%) was characterized by GC-FID (Gas Chromatography with Flame Ionization Detector) and GC-MS (Gas Chromatography coupled to Mass Spectrometry) showing a composition close to that currently accepted for Spanish sage essential oil in the European Pharmacopoeia, ISO (International Standard Organization) and UNE (Una Norma Española) standards, with 1,8-cineole (13.7-45.7%) and camphor (12.1-28.6%) as major constituents. HPTLC methods, based on the analysis of hydroalcoholic and dichloromethane extracts, allowed to distinguish SB from other Salvia taxa currently found in Valencia region, except from its hybrid SH. This interdisciplinary study, that combines popular knowledge with botany and chemistry, allows to identify the raw herbal material from SB and to distinguish it from other Salvia species, ensuring a proper commercialization as herbal teas or for the preparation of spirits.

HPTLC Fingerprinting and Cholinesterase Inhibitory and Metal-Chelating Capacity of Various Citrus Cultivars andOlea europaea.

Inhibitory activity of thirty-one ethanol extracts obtained from albedo, flavedo, seed and leaf parts of 17 cultivars of Citrus species from Turkey, the bark and leaves of Olea europaea L. from two locations (Turkey and Cyprus) as well as caffeic acid and hesperidin was tested against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), related to the pathogenesis of Alzheimer's disease, using ELISA microtiter assays at 500 µg/mL. Metal-chelating capacity of the extracts was also determined. BChE inhibitory effect of the Citrus sp. extracts was from (7.7±0.7) to (70.3±1.1) %, whereas they did not show any inhibition against AChE. Cholinesterase inhibitory activity of the leaf and bark ethanol extracts of O. europaea was very weak ((10.2±3.1) to (15.0±2.3) %). The extracts had either no or low metal-chelating capacity at 500 µg/mL. HPTLC fingerprinting of the extracts, which indicated a similar phytochemical pattern, was also done using the standards of caffeic acid and hesperidin with weak cholinesterase inhibition. Among the screened extracts, the albedo extract of C. limon 'Interdonato', the flavedo extracts of 'Kara Limon' and 'Cyprus' cultivars and the seed extract of C. maxima appear to be promising as natural BChE inhibitors.

St. John's Wort versus Counterfeit St. John's Wort: An HPTLC Study.

Hypericum perforatum L. is the most commonly used herb for treating depression. Due to the popularity of this botanical, there is a potential for economically driven adulteration of St. John's wort (SJW) products. The goal of this study was to investigate SJW ingredients suspected to be adulterated based on simple preliminary HPTLC tests. Commercial samples were analyzed by HPTLC following the United States Pharmacopeia (USP) monograph methodology, with additional visualization under white light. A number of these samples presented odd methanolic solution colors and unconventional HPTLC fingerprints, suggesting the presence of other species and/or extraneous polar additives. To achieve identification and separation of the polar additives, a new reversed-phase HPTLC method was developed. The adulterants were identified as synthetic dyes in the amounts of 0.51 to 1.36% by weight. Identities of the dyes were confirmed by scanning densitometry and HPTLC-MS. A modified USP method with additional detection mode permitted the identification of eight SJW samples adulterated with dyes and six others with flavonoid fingerprints different from those specified by USP from a total of 37 samples of dry extracts, finished products, and bulk raw herb. A decision flowchart is proposed to guide the detection of adulteration of SJW in a systematic fashion.

The authenticity and quality of Rhodiola rosea products.

BACKGROUND: Rhodiola rosea L. Crassulaceae, root (Golden Root, Arctic Root) is a high-value herbal medicinal product, registered in the UK for the treatment of stress-induced fatigue, exhaustion and anxiety based on traditional use and used throughout Europe as a herbal medicinal product for similar indications. Numerous unregistered supplements are also available. There are several Chinese species used in traditional Chinese medicine (TCM), including Rhodiola crenulata (Hook.f. & Thomoson) that is believed to be a common adulterant in the R. rosea value chain. AIMS: The project is embedded in a larger study aiming to investigate the diverse value chains that lead to the production of R. rosea as an herbal medicinal product or supplement. Here we focus on a comparison of the quality of the finished products and assess any phytochemical variation between products registered under the Traditional Herbal Medicine Products Directive (THMPD) and products obtained from the market without any registration (i.e. generally unlicensed supplements). Our key aim is to establish the extent of the problem in terms of adulteration of consumer products claiming to contain R. rosea (or R. crenulata). METHODS: Approximately 40 commercial products (granulated powders and extracts) were sourced from different suppliers. We analysed these samples using high performance thin layer chromatography (HPTLC), mass spectrometry (MS) and (1)H NMR spectroscopy coupled with multi-variate analysis software following a method previously developed by our group for the analysis of turmeric products. RESULTS: We investigate the phytochemistry of the different species and assess the potential of R. crenulata as an adulterant at the end of the R. rosea value chains. The consistency of the products varies significantly. Approximately one fifth of commercial products that claimed to be R. rosea did not contain rosavin (the key reference markers used to distinguish R. rosea from related species). Moreover some products appeared not to contain salidroside, another marker compound found in other Rhodiola species. Approximately 80% of the remaining commercial products were lower in rosavin content than the registered products and appeared to be adulterated with other Rhodiola species. CONCLUSIONS: The variation in phytochemical constituents present in Rhodiola products available to European buyers via the internet and other sources is a major cause for concern. Adulteration with different species, and other sometimes unknown adulterants, appears to be commonplace. Good quality systems and manufacturing practices, including those required under the THMPD, enable consumers to have confidence that products are authentic and meet a high specification for quality and safety.

Simultaneous Detection of Three Phosphodiesterase Type 5 Inhibitors and Eight of Their Analogs in Lifestyle Products and Screening for Adulterants by High-Performance Thin-Layer Chromatography.

An HPTLC method is proposed to permit effective screening for the presence of three phosphodiesterase type 5 inhibitors (PDE5-Is; sildenafil, vardenafil, and tadalafil) and eight of their analogs (hydroxyacetildenafil, homosildenafil, thiohomosildenafil, acetildenafil, acetaminotadalafil, propoxyphenyl hydroxyhomosildenafil, hydroxyhomosildenafil, and hydroxythiohomosildenafil) in finished products, including tablets, capsules, chocolate, instant coffee, syrup, and chewing gum. For all the finished products, the same simple sample preparation may be applied: ultrasound-assisted extraction in 10 mL methanol for 30 min followed by centrifugation. The Rf values of individual HPTLC bands afford preliminary identification of potential PDE5-Is. Scanning densitometry capabilities enable comparison of the unknown UV spectra with those of known standard compounds and allow further structural insight. Mass spectrometric analysis of the material derived from individual zones supplies an additional degree of confidence. Significantly, the proposed screening technique allows focus on the already known PDE5 Is and provides a platform for isolation and chemical categorization of the newly-synthesized analogs. Furthermore, the scope could be expanded to other therapeutic categories (e.g., analgesics, antidiabetics, and anorexiants) that are occasionally coadulterated along with the PDE5-Is. The method was successfully applied to screening of 45 commercial lifestyle products. Of those, 31 products tested positive for at least one illegal component (sildenafil, tadalafil, propoxyphenyl hydroxyhomosildenafil, or dimethylsildenafil).

Prevention of False-Positive Results: Development of an HPTLC Autographic Assay for the Detection of Natural Tyrosinase Inhibitors.

A simple and rapid high-performance thin-layer chromatography-based autographic assay was established to screen plant extracts for the presence of tyrosinase-inhibiting substances. Three mobile phases were selected for the chromatographic separation of different types of extracts. After development, the plate was sprayed with the substrate solution Levodopa followed by a solution of the enzyme tyrosinase. Several known tyrosinase inhibitors were tested simultaneously as positive controls. They were detected as white spots with white light in remission from the plate as well as with white light transmitted through the plate. Some of the investigated extracts included spots showing a different behaviour; some lipophilic substances appeared as white spots in white light remission but were black in white light transmission. This behaviour, which could lead to false-positive results, was due to poor wettability of the corresponding spots. False-positive results were eliminated by adding Triton X-100 to the Levodopa solution and drying the plate after 10 minutes incubation with a molecular sieve. Tyrosinase inhibitors can be clearly identified as white spots against a dark background in white light remission as well as in white light transmitted through the plate. The established high-performance thin-layer chromatography autographic assay was validated and can be used as a standard method for the detection of tyrosinase inhibitors in plant extracts without causing false-positive results.

Chemical variability along the value chains of turmeric (Curcuma longa): a comparison of nuclear magnetic resonance spectroscopy and high performance thin layer chromatography.

ETHNOPHARMACOLOGICAL RELEVANCE: Herbal medicine value chains have generally been overlooked compared with food commodities. Not surprisingly, revenue generation tends to be weighted towards the end of the chain and consequently the farmers and producers are the lowest paid beneficiaries. Value chains have an impact both on the livelihood of producers and on the composition and quality of products commonly sold locally and globally and consequently on the consumers. In order to understand the impact of value chains on the composition of products, we studied the production conditions for turmeric (Curcuma longa) and the metabolomic composition of products derived from it. We aimed at integrating these two components in order to gain a better understanding of the effect of different value chains on the livelihoods of some producers. MATERIALS AND METHODS: This interdisciplinary project uses a mixed methods approach. Case studies were undertaken on two separate sites in India. Data was initially gathered on herbal medicine value chains by means of semi-structured interviews and non-participant observations. Samples were collected from locations in India, Europe and the USA and analysed using (1)H NMR spectroscopy coupled with multivariate analysis software and with high performance thin layer chromatography (HPTLC). RESULTS: We investigate medicinal plant value chains and interpret the impact different value chains have on some aspects of the livelihoods of producers in India and, for the first time, analytically assess the chemical variability and quality implications that different value chains may have on the products available to end users in Europe. There are benefits to farmers that belonged to an integrated chain and the resulting products were subject to a higher standard of processing and storage. By using analytical methods, including HPTLC and (1)H NMR spectroscopy, it has been possible to correlate some variations in product composition for selected producers and identify strengths and weaknesses of some types of value chains. The two analytical techniques provide different and complementary data and together they can be used to effectively differentiate between a wide variety of crude drug powders and herbal medicinal products. CONCLUSIONS: This project demonstrates that there is a need to study the links between producers and consumers of commodities produced in so-called 'provider countries' and that metabolomics offer a novel way of assessing the chemical variability along a value chain. This also has implications for understanding the impact this has on the livelihood of those along the value chain.