Pitfalls and promises of raw drug identification techniques in the ayurvedic industry: an overview

Abstract

India, with a rich heritage of floral diversity, is well-known for its medicinal plant wealth and is the largest producer of medicinal herbs in the world. Ethnobiological Survey of Ministry of Environment and Forests (MOEF) could identify 8000 plant species utilized in various systems of medicine with approximately 25,000 effective herbal formulations. The extensive consumption to meet demand–supply ratio exerts a heavy strain on the existing resources. This subsequently led to the adulteration and substitution of medicinal plants with look-alike species. The consumer’s faith on herbal medicine is in the phase of decline due to the extremities in adulteration/substitution and ensuing consequences. It is imperative to bring forth universally acceptable standard tools to authenticate raw drugs before being processed further into formulations. A vast array of techniques such as physical, chemical (analytical), biochemical, anatomical, organoleptic, and recently emerged DNA based molecular methods are widely used for plant species authentication. In recent years, DNA barcoding has made remarkable progress in the field of medicinal plants research. DNA metabarcoding is the latest development for qualitative evaluation of the herbal formulations, whereas for quantitative analysis, combination of pharmacognostic, pharmacovigilance and analytical methods are inevitable for authentication. This review addresses the overall strengths and shortcomings of the existing as well as recently emerged techniques in authenticating ayurvedic raw drugs.

Introduction

India, with a rich heritage of floral diversity, is well-known for its medicinal plant wealth and is the largest producer of medicinal herbs in the world (Ganesan et al. 2016). According to World Health Organization (WHO), 21,000 medicinal plant species are used for various medicinal purposes around the world. The healing properties of plants are well documented in Rigveda (400–1500 B.C.), Atharvaveda (1500 B.C.) and Upanishad (1000 B.C.) (Patil and Patil 2010). In India, ethnobiological survey of MOEF could identify 8000 plant species utilized in various systems of medicine with approximately 25,000 effective herbal formulations (Mishra et al. 2016). Consequent high demand involving 960 actively traded and 178 species traded in bulk quantities, an estimate of 90 per cent of wild resources are utilized by more than 8610 traditional manufacturing units (Goraya and Ved 2017).

The extensive consumption to meet demand–supply ratio exerts a heavy strain on the existing resources with a few of them increasingly threatened in their natural habitat (Chen et al. 2018). Adulteration/substitution of these commercial resources with inferior taxa has become a common practice to meet the annual demand of ayurvedic industry (Mishra et al. 2016; Ouarghidi et al. 2012; Techen et al. 2014; Walker and Apple Quist 2012). However, to guarantee the quality of herbal medicines, WHO pharmacopoeia has implemented certain criteria for proper identification of plant species and quality assessment of potent phytochemical principles (Palhares et al. 2015). Although there are several recommended methods, right from the traditional taxonomic to organoleptic and physiochemical, it is extremely difficult to authenticate ayurvedic raw drugs. This is because these raw drugs are available as shredded, powdered and extremely dried forms in the market which are hard to identify in the preliminary screening (Coghlan et al. 2012). Adulteration and substitution is currently a major concern with confirmed reports from several countries (Coghlan et al. 2012; Newmaster et al. 2013; Urumarudappa et al. 2016). Scientific studies have estimated 46–66 per cent of herbal adulteration in North America and around 80 per cent of adulteration in Africa (Han et al. 2016). India, however, does not have any published data to estimate the extent of adulteration in herbal products (Shanmughanandhan et al. 2016). The consumer’s faith on herbal medicine is in the phase of decline due to the extremities in adulteration/substitution and subsequent consequences (Palhares et al. 2015). Therefore, it is imperative to bring forth universally acceptable standard tools to authenticate raw drugs before being processed further into formulations. Many researchers have diverted their focus towards the multi-tiered or integrated approach, by amalgamating already existing methods which are yet to be fine-tuned (Palhares et al. 2014, 2015; Raclariu et al. 2018; Seethapathy et al. 2018; Urumarudappa et al. 2016).

This review addresses the overall strengths and shortcomings of the existing as well as recently emerged techniques in authenticating ayurvedic raw drugs.

Herbal market

Herbal medicine industry is one of the fastest growing industries in the world. Herbal products such as phytopharmaceuticals, phytocosmetics and personal care products have always attracted global attention. Europe leads the herbal market followed by Asia, North America and Japan. China and India are the top exporters, whereas Hong Kong, USA and Germany are the principal importers (Nirali and Shankar 2015). Global market for herbal medicine is estimated to be worth US$ 83 billion with Europe being the main herbal market in the world. Studies forecast that by 2020, herbal market will hit the target of US$ 3 trillion and by 2050 it is predicted to reach US$ 5 trillion (Bangladesh foreign trade institute 2016).

In India, around 8610 recognised, 50 large scale, 200 medium scale and 8360 small scale herbal manufactures have been recorded (Goraya and Ved 2017). Indian herbal industry has demonstrated it’s pre-eminence with 15 per cent more annual turnover than that of pharmaceutical industry. 1,95,000 MT of herbal raw drugs are consumed by the herbal industries in India and almost 5,12,000 MT of raw herbal drug had been exported from India during the years 2014–15, Which is more than double with an increase of 138 per cent compared to previous years (Goraya and Ved 2017). Raw herbal drugs traded commercially are regulated and controlled by various measures, which vary from country to country. Species protection is one of the most important measures regulating the international trade of medicinal plants. CITES, an international treaty proposed by World Union Conservation has established protocols for regulating international trade ensures trade of specimens without threat to their survival.

In India, owing to the massive demand of herbal industries, unscientific extraction of medicinal plants from wild approximates to around 80 per cent (Ved and Goraya 2007). This ultimately led to overexploitation of resources, which is a serious threat to the species survival, also affecting the livelihood of people relying on these resources. Inaccessibility to potent ayurvedic raw drugs has led to adulteration and substitution of these drugs with its close relative or look alike species jeopardizing the quality. Thus, it is essential to develop tools to check authenticity of drugs used in the market. Moreover, conservation, restoration and sustainable management of available resources in wild could be a viable option to curb adulteration to an extent.

Raw drug adulteration

India has a rich history of traditional medicines, of which, Ayurveda is considered as one of the most ancient and widely accepted systems. Wide popularity of Ayurveda has contributed herbal industry to become the most flourishing sector in the world. The recent boost in utility of herbal products apparently augmented misuse and adulteration of medicinal plants leading to consumers’ and manufacturers’ discontent with fatal consequences in some instances. The absence of an effective regulatory framework to evaluate quality, authenticity and safety of raw drugs available in the market and the derived herbal formulations lead to severe health issues in consumers worldwide (Srirama et al. 2017). Medicinal products containing nephrotoxic and carcinogenic aristolochic acids were banned in Belgium, UK, Canada, Australia, and Germany (Zhou et al. 2013). In Australia, Japan, Taiwan and China, chronic use of Aristolochia fangchi adulterated products apparently led to the death of patients (Hong et al. 2006; Yang et al. 2002). Several studies has reported the adulteration of Stephania tetrandra (Fang-Ji) roots with roots of the toxic herb, Aristolochia fangchi (Guang-Fang-Ji) leading to major renal failure (Jadot et al. 2017; Michl et al. 2013). Similarly, Mesua ferrea was adulterated with Calophyllum inophyllum (Poornima 2010), Piper nigrum with Lantana camara and Embelia ribes (Dhanya and Sasikumar 2010), Papavar somniferum with Amaranthus paniculatas (Dhanya and Sasikumar 2010), Santalum album with Erythroxylum monogynum (Chembath et al. 2012), Gloriosa superba with Ipomea species (Kumar et al. 2018) as well as Cassia fistula was adulterated with Senna auriculata (Seethapathy et al. 2015). In 2002, the US Food and Drug Administration received several reports of liver-related injuries such as hepatitis, cirrhosis, and liver failure due to consumption of Piper methysticum containing products which was subsequently banned in Germany, Switzerland, France, Canada and UK (US Food and Drug Administration 2001). One of the few causes of adulteration is misidentification and similarity in the local name between the species. These reports accentuate the necessity for proper raw drug identification, certification and toxicity assessment along with active pharmacovigilance of herbal products (Dutta et al. 2018). Therefore, identifying a comprehensive method for effective monitoring of raw herbal drugs is a pre-requisite.

Substitution in ayurveda

Ayurvedic manuscripts such as Bhavaprakasha, Yogaratnakara and Bhaishajya Ratnavali, had recognized the importance of species substitution (Pratinidhi dravya) (Sastri 2001; Shastri 2005; Chunekara et al. 2010). The concept of substitutes ideally is a measure based on their biological and chemical equivalence to overcome the species unavailability (Hegde 2018). Since ayurvedic medicines are characterized based upon the principles of taste, properties, potency and unique pharmacological action, more than 150 pradinidhi dravyas are mentioned in the ayurvedic scripts (Nagarajan et al. 2015). For instance, Saussurea lappa is considered as valid and equally effective substitute of Inula racemosa, likewise Pterocarpus santalinus and Cinnamomum chomphora are considered as substitutes for Santalum album, Schlechera oleosa for Crocus sativus, Woodfordia fruticosa for Glycyrrhiza glabra, Syzygium aromaticum for Myristica fragrans, Terminalia myriocarpa for Terminalia arjuna, Abies webbian for Taxus baccata and Gmelina arborea for Vitis vinifera, among others, owing to their similarity in morphology and chemical principles (Sastri 2001). However, the term ‘substitution’ has been exploited in a wrong sense to cope up with the rising demand, wherein several adulterants with inferior chemical properties are often utilized as substitutes. Pterocarpus santalinus (Rakthachandana) used for digestive disorder was substituted with root of Vetiveria zizanioides (Ushira), though the major chemical component was entirely different (Mishra 2007). Similarly, Cyperus rotundus, a common weed, is mentioned as substitute for Aconitum heterophyllum, an endangered species found in Himalayas (Gupta et al. 2006). However, in Indian markets, the recommended substitute Cyperus rotundus was adulterated with inexpensive and commonly available Cryptocoryne spiralis and Cyperus scariosus (Ved and Goraya 2007). Therefore, adulteration of medicinal plants and their authentic substitutes with inferior plant species even regardless of its chemical attributes is an illegitimate practice.

The intentional/illegal substitution irrespective of the pharmacological effects/bio equivalency can be considered as adulteration with serious consequences (Srirama et al. 2017). Recently, instances of drug resistance and side effects of ayurvedic drugs are widely reported jeopardizing the trust in ayurvedic system of medicine (Thatte and Bhalerao 2008; Srirama et al. 2017). Hence, efficacy, safety and therapeutic potential of substitutes need to be checked via detailed pharmacokinetic and clinical trials before the drug formulations reach the consumers. In addition, unavailability of the desired taxa owing to overexploitation is a major concern and effective strategies for sustainable utilization and conservation of such species only would assure its availability in the ensuing years.

Traditional vs. modern methods

A vast array of techniques such as physical, chemical (analytical), biochemical, anatomical, organoleptic, and recently emerged DNA based molecular methods are widely used for plant species authentication. Traditional taxonomic system mostly emphasizes on morphology and anatomy of the species. However, recent studies have shown the influence of environmental and climatic variables in shaping the morphology and anatomy of species (Li et al. 2019, 2020), which makes species discrimination, a tedious job. The lack of expertise, phenotypic plasticity and species delimitation make the taxonomic identification system more complicated especially in families like Papaveraceae, Poaceae, Malvaceae and Cactaceae (Vohra and Khera 2013). Macroscopic evaluation deals with features such as shape, size, colour, texture, surface characterisation, odour, and organoleptic properties (Chanda 2014). Whereas, microscopy involves phloem and xylem characteristics, number and structure of stomata. Since raw drugs are available in extremely dried, shredded or powdered form, species identification using traditional tools may not always possible. Moreover, close relationships shared by the adulterants/substitutes with the original raw material often lead to erratic results (Palhares et al. 2015). In many instances, chromatographic finger printing techniques such as TLC (Thin-layer chromatography), HPTLC (High-performance thin layer chromatography), HPLC (High Performance Liquid Chromatography), GC–MS (Gas chromatography–mass spectrometry), NMR (Nuclear magnetic resonance spectroscopy), FTIR (Fourier-transform infrared spectroscopy) were used as qualitative as well as quantitative methods for authentication of medicinal plants (Meena et al. 2018; Shawky and Selim 2018; Singh et al. 2020; Yao et al. 2020). However, chemical fingerprints are influenced by external environmental factors such as age of plant and storage conditions as well as type of plant parts used (Kaur et al. 2016; Liu et al. 2016). During early 1990s, researchers shifted their focus to DNA based markers for molecular species identification (Sucher and Carles 2008; Hao et al. 2010). A wide range of molecular markers such as AFLP (Amplified fragment length polymorphism), RFLP (Restriction fragment length polymorphism), RAPD (Random amplification of polymorphic DNA), ISSR (Inter simple sequence repeat), SSR (Simple sequence repeat), SCAR (Sequence characterized amplified region), LAMP (Loop mediated isothermal amplification), SNPs (Single nucleotide polymorphisms) were extensively used for identification of plants (Cao et al. 2010; Diao et al. 2009; Sharma et al. 2008; Tamhankar et al. 2009). DNA markers gained popularity for its accuracy and proper identification as it remained unaffected by physiological or environmental factors (Ganie et al. 2015). Each DNA marker has its own advantages and limitations and none of them can be considered as ideal. Selection of markers is purely based on the nature of research, financial stability and technical expertise (Kiran et al. 2010). Many reviews have provided ample insights into the principles, applications and technicalities of molecular markers (Nybom et al. 2014; Sharma et al. 2018; Tharachand et al. 2012).

Chromatography techniques are frequently used for discovery, development and manufacture of pharmaceuticals, which complements taxonomy for authentication in plants (Abubakar et al. 2018). Many progressive analytical techniques have been introduced to appraise the quality of herbal medicine such as HPLC, GC, UHPLC (Ultra high performance liquid chromatography), TLC, along with the recently hyphenated techniques like HPLC–DAD (diode-array detector), GC–MS, CE-DAD (Capillary electrophoresis) HPLC–MS and HPLC-NMR for additional spectral information and structural elucidation (Bansal et al. 2014). Amongst the commonly used methods such as TLC, HPTLC, HPLC and GC, TLC is the fastest method for chemical profiling in various pharmacopoeias viz. AHP, Chinese drug monographs and Pharmacopoeia of the People’s Republic of China, etc. (Patel and Patel 2016). HPTLC is an alternative for TLC, with improved resolution, accuracy and reproducibility. The steroid diversity of Aerva lanata was revealed using HPTLC profile and used to differentiate the original species from its adulterants (Mariswamy et al. 2011). Fingerprinting of Cinnamomum cassia, Cinnammomum zeylanicum, Ruellia tuberosa, Solena amplexicaulis, Aerva lanata and Tragia plukenetii was performed using HPTLC (Chothani et al. 2012; Karthika and Paulsamy 2015; Meena et al. 2018; Singh et al. 2018). HPLC is another automatable technique with high rate of precision, resolution, sensitivity and selectivity. Several studies including authentication of Indian species Talisapatra with English yew (Taxus baccata), chromatographic profiling of Woodfordia fruticosa and Tabernaemontana catharinensis, active metabolites of Annona muricata, quantitative analysis of phenolic acids, flavonoids and ascorbic acid of wild edible leaves are some of the studies performed with HPLC (Boligon et al. 2015; Seal 2016; Syed and Khan 2016; Vadivel et al. 2018). In addition, presence and quantification of toxic chemicals from plant species such as aristolochic acids in Aristolochia, norditerpenoid alkaloids in Delphinium spp, and identification of five hepatotoxic pyrrolizidine alkaloids in traditional Chinese medicinal herb, Herba senecionis var. scandentis, have been identified using HPLC (Araya et al. 2018; Li et al. 2008). HPLC is possible to hyphenate with other detectors such as UV, DAD, for herbal finger printing and NMR for metabolomic profiling (Kamboj and Saluja 2017). GC/hyphenated GC/MS is one of the most efficient, reproducible and well used analytical platforms, owing to its robust, reproducible and selective nature of the technique as well as the large number of well-established libraries. GC–MS was successfully employed for the analysis of essential oils (thymus species, Ocimum basilicum L, Peucedanum praeruptorum), terpenes (Salvia spp., Myrtus communis L) and chemotaxonomy studies (Ibrahim et al. 2019; Mori et al. 2018; Nickavar et al. 2016; Sajjadi 2012; Siracusa et al. 2018). Even though there are different chromatographic methods, it is impossible to develop appropriate analytical method to represent chemical characteristics of multi-herbal products. In these circumstances, combination of analytical methods following different separation principle was recommended by FDA.

DNA barcoding offers a novel prospective tool for taxonomists and has greatly transformed species identification process (Hebert et al. 2003). It is an accurate and reliable alternative to morphological identification of biological material in challenging situations (Chen et al. 2010; Hebert et al. 2003). It can overcome inherent problems associated with traditional taxonomic identification due to phenotypic plasticity, species complexity, difficulty in finding reliable characters due to long maturity period, etc. (Kress et al. 2005). In plants, matK barcode region is one of the most rapidly evolving coding region of plastid genome similar to the COI used in animals (Hollingsworth 2011). However, in spite of several successful studies, matK was found to have poor species discriminatory power in some taxa (CBOL, 2009; Hidalgo et al. 2004). Though several barcode regions such as rbcL, psbA-trnH and ITS were successful in most instances, single tier approach was not encouraged owing to its inability to resolve in the species level (CBOL 2009; Doebley et al. 1990). Furthermore, combination of two or more barcode regions was initiated and higher efficiency of multi-locus approach was demonstrated in subsequent studies (Fazekas et al. 2008; Kress and Erickson 2007). In 2009, CBOL recommended matK + rbcL as universal standard barcode region with ITS and psbA- trnH region as complementary barcodes for land plants. Combination of rbcL + ITS region that enables higher retrieval capacity is widely used for identification of herbal products (Burgess et al. 2011; Hollingsworth et al. 2009; Ismail et al. 2008; Krawczyk et al. 2013; Malik et al. 2018; Newmaster et al. 2006, 2013).

In recent years, DNA barcoding has made remarkable progress in the field of medicinal plants research. DNA barcoding was initially used as identification tool and lately for the quality assurance of herbal products (Raclariu et al. 2017a). Herbal product authentication study shows disparity between the labelled product and the barcoding results. Using DNA barcoding, significant amount of adulteration was found in 98 per cent of Traditional Chinese Medicine products, 26 per cent adulterant herbal products from Iran, 16 per cent substitution of dietary herbal supplements from US and 50 per cent Cassia product adulteration from India (Ghorbani et al. 2017; Little 2014; Seethapathy et al. 2015). Recent studies revealed wide spread adulteration in raw herbal drugs such as Saraca asoca, Sida cordifolia, Garcinia, Mormodica charantia, Myristica fragrans and Santalum album (Dev et al. 2013; Kumar et al. 2020; Seethapathy et al. 2018; Swetha et al. 2017 Urumarudappa et al. 2016; Vassou et al. 2015). It is a major concern in almost all countries dealing with herbal drugs. In the present context, British pharmacopeia has implemented first globally general DNA barcoding method as a tool for authentication given its ability to identify source of the herbal product accurately compared to traditional methods. (Heinrich et al. 2018; Sgamma et al. 2018).

DNA barcoding with HRM (High resolution melting) is a recently emerged trend in herbal species identification (Mishra et al. 2018; Osathanunkul et al. 2015). In this method, based on the principle of fluorescence, denaturation and renaturation switches on and off accessibility of intercalating dye, enabling fluorescence detection only during duplex formation. A major advantage of Bar-HRM (Barcode HRM) analysis is easy detection of single base variants or species specific differences in a short region of DNA (Sun et al. 2016). Moreover, HRM analysis with its easiness in use, flexibility, low cost, high sensitivity and specificity is an approachable method for authentication of herbal products, food products and bacterial identification (Ganopoulos et al. 2013; Miller et al. 2015; Ongchai et al. 2019; Osathanunkul et al. 2015; Sun et al. 2016; Tong et al. 2014). The first report on BAR-HRM coupled with DNA barcode was used to discriminate Sideritis species (Kalivas et al. 2014). Later, psbA –trnH region coupled with HRM was used for authentication of Radix notoginseng (Tong et al. 2014). Reduced length of rbcL sequence as mini barcodes in HRM provided enough information to identify closely related species (Costa et al. 2016). rbcL mini barcodes with redesigned primer showed good discrimination in three medicinal plant species of Acanthacea family (Osathanunkul et al. 2015). DNA barcoding coupled with HRM was used to discriminate the species composition of Senna alexandrina from the market samples (Mishra et al. 2018). Authentication of Hypericum perforatum and Hypericum. androsaemum in herbal infusions was also done using HRM analysis using matK as mini barcode (Costa et al. 2016).

Authentication of processed, multi-herbal mixture available in the market is extremely difficult using conventional DNA barcodes. DNA metabarcoding which is a combination of high throughput sequencing and DNA barcoding was introduced to resolve this problem (Dormontt et al. 2018). It enables multi-taxa identification using total DNA from complex mixture (Seethapathy et al. 2019; Staats et al. 2016; Zhang et al. 2020). DNA metabarcoding is applicable for identification of plant diversity in the available market products and also to scrutinise the level of inconsistency detected in plant species based on the label claims of marketed products (Ivanova et al. 2016; Raclariu et al. 2017a, b; Seethapathy et al. 2019). Metabarcoding analysis of market samples of Echinacea species, Hypericum perforatum, Veronica officinalis and Pueraria montana showed wide spread adulteration (Raclariu et al. 2017a, b; Zhang et al. 2020). The composition of 15 highly processed Traditional Chinese Medicine using DNA metabarcoding revealed the presence of adulterant species (Orchid species, Decalepis, and Nepenthes species) which are included in CITES appendices I and II (Coghlan et al. 2012). DNA metabarcoding can be used for qualitative evaluation of the herbal formulations, whereas in quantitative analysis, combination of pharmacognostic, pharmacovigilance and analytical methods are inevitable for authentication of herbal species and products (Heinrich et al. 2018; Mishra et al. 2016; Parveen et al. 2016; Pawar et al. 2017; Schmiderer et al. 2017).

Integrated approach

Currently, quality control and safety analysis of herbal drugs and mixtures are progressing in a comprehensive and integrated direction. Conventional and single tire approaches are in the phase of decline and nowadays focus has been shifted towards integrated approaches. Integrated method is a combination of two or more diverse techniques which are capable of authenticating a species more precisely. Recently, it is shown that in addition to adulteration, lack of potent principles in the processed products could also be a serious threat to Ayurveda or traditional system of medicine (Palhares et al. 2015). The efficiency of integrated approach involving DNA barcoding and HPTLC was demonstrated in the analysis with 257 samples derived from 8 species recommended by WHO (Palhares et al. 2014). A combination of DNA barcoding and NMR was also performed in species adulteration of Garcinia species and Sarca asoca (Urumarudappa et al. 2016; Seethapathy et al. 2018). For the conservation and proper use of Brazilian quinas, a comprehensive system of chemical, biological and molecular methods have been used (Palhares et al. 2015). Comprehensive approach of DNA metabarcoding, TLC and HPLC–MS was carried out for the detection of substitution/adulteration of Hypericum perforatum (Raclariu et al. 2017a, b). Authentication of Marsdenia suaveolens, was also successfully done using a multi-tier approach of DNA barcoding coupled with TLC and HPLC (Yu et al. 2018). Integrated approach would be a future promising tool for accurate and reliable qualitative/quantitative authentication of medicinal plants and products.

Bioprospecting: a future perspective for natural resources

The global resurgence in the use of herbal remedies has increased the demand for medicinal plants and herbal products. The huge market demand has resulted in over exploitation of the species as most of them are being consumed and consequently exhausted at a much faster rate than it is being replenished. To ensure safety and quality of ayurvedic formulations, modern techniques which guarantee sustainable management and survival of medicinal plants is necessary (Shanmuganandhan et al. 2016). Bioprospecting could be a major breakthrough in this regard, which utilizes the traditional knowledge through ethno-pharmacological investigations for sustainable use of natural resources (Rastogi and Kaphle 2011; Sharma et al. 2013; Purkayastha 2016; Hemant Sood 2020). The development of modern techniques such as genetic engineering, advancements in culture techniques and fermentation has led to the large-scale biosynthesis of highly efficient bioactive natural products (Chen et al. 2018). Thus, prospecting of diverse traditional knowledge also contributes to a valuable lead in developing novel drugs/pharmaceuticals or phytochemicals or genes of great industrial value (Efferth et al. 2016; Pushpangadan et al. 2018). Bioprospecting has been effectively utilized for the large scale production of medicinally active compounds such as artemisinin, crofelemer, prostratin, vinblastine and vincristine (Cox and King 2013). Furthermore, a multi-omic approach involving genomics, proteomics, metabolomics and transcriptomics would also enable us to identify the potential genes involved in the biosynthetic pathway and upscaling of secondary metabolite production through upregulation/downregulation of the specific genes involved (Medema and Fischbach 2015; Rai et al.2017). Thus, integration of innovative techniques along with broader perspective of Ayurveda could confine the resource limitation and extensive utilization of natural resources.

Conclusion

Most herbal drugs available in the market are sourced from the wild through supply chains in the formal or informal sectors. The unscientific collection and overexploitation without evaluating the resource abundance lead to endangerment of the potent species in the natural habitat. CITES recommendations without harming the biodiversity is apparently ignored while performing species collection. The resource limitation owing to escalating demand leads to adulteration/substitution with plants/plant parts of inferior properties. Therefore, to ensure safety and quality of ayurvedic formulations, standard techniques in practice warrant more consistency and precision. Herbal drugs, its substituents and adulterants have been studied at length using various techniques but an ideal strategy to safeguard its utility is yet to be defined. Most of the methods implemented so far have focused on single tier approach which may not to be feasible to address this challenging issue. Therefore, a multi-tier approach integrating the already existing as well as advanced techniques would be a better alternative. Raw drugs available in the market need to be analysed critically prior to its processing into formulations. Along with the recommended standard organoleptic and analytical methods in raw drug authentication, an integrated approach involving a molecular tool can strengthen the existing practice of quality checking. Recommendation of a universal tool may not be practical in herbal industry as the analytical methodology solely depends on the type of raw material and the product derived. Though ayurvedic medicine has gained much popularity in India and all around the world, proper certification agencies are yet to be established. Herbal medicine once formulated is easily available to the public through various portals, where no mention of any clinical trials or proper way of administration is cited. It is, therefore, important to bring forth a statutory body to monitor proper collection, processing, production and sale of herbal medicine. Concurrently, scientific management, restoration and conservation measures along with bioprospecting of natural resources are being acclaimed for the biological conservation, which should be given utmost priority to augment the depletion of wild resources as well as to meet the rapidly increasing demand of the herbal industries.

Abbreviations

MOEF

Ministry of environment and forests

WHO

World health organization

CITES

Convention on international trade in endangered spices of wild fauna and flora

AHP

American herbal pharmacopoeia

FDA

Food and drug administration

Author contribution

SAD: Writing of Review article. RJ: Writing of Review Article. RU: Writing of Review Article.

Compliance with ethical standards

Conflict of interest

The authors declare no conflict of interests.