India is home to some of the oldest civilizations, during which period the local communities domesticated indigenous plant species for food and agriculture and medicinal uses. In this process, they also bio-prospected and/or absorbed potentially valuable exotic plant species, making them integral part of Indian culture, including the traditional medicinal system, the Ayurveda. The present paper discusses the absorption of 26 plant species of exotic origin, before 8th century, as evidenced by archaeological sculptural or botanical remains and documentation of such plants in Sanskrit, the Vedic language. Occurrence and/or introduction of such plants at such distant places in ancient times is visualized as a result of geographical continental fragmentation followed by drift, natural or man-made transoceanic movement, and cultural and trade exchange of plant material over time and space.

Scientific research has always been concerned with aspects of human health. There are several systems of medicines besides the globally accepted allopathy, which are based on compounds originating from natural products. Recent research has been centred around validation of the traditional knowledge on medicinal products. The traditional systems in India, China and forklore medicines in other parts of the world have indicated the potential of natural products consist of various chemical compounds that could be used as drugs. The search for drugs against five major dreadful diseases namely, cancer, AIDS, heart disease, diabetes and pulmonary disorders that attack the present day human from natural products has been in progress for some time. Microbes, plants and animals are the sources of natural products. In the past five decades, the research on bioactive chemicals from marine algae has been incited and several compounds with biological activity were isolated from algae. Generally, these are secondary metabolites produced for chemical defence against the biotic pressure of predators, consumers and epibionts. These potential drugs are now attracting considerable attention from the pharmaceutical industries due to the necessity of identifying substances that could be utilized for novel therapeutic purposes. Several compounds such as alginate, carrageenans, sulphated and halogenated polysachcharise and other derivatives have been shown to provide drugs that could be antiviral, anticancer and antimicrobial. The present account is on the potential of marine macro-algae for medicinally important products.

Bioprospecting is the search for valuable products from natural sources. Given that most species are poorly known, a key question is where to search. Ethnodirected bioprospecting approaches use traditional knowledge in the process of selecting plants to screen for desired properties. A complementary approach is to utilize phylogenetic analyses based on traditional uses or known chemistry to identify lineages in which desired properties are most likely to be found. Novel discoveries of plant bioactivity from these approaches can aid the development of treatments for diseases with unmet medical needs. For example, neurological disorders are a growing concern, and psychoactive plants used in traditional medicine may provide botanical sources for bioactivity relevant for treating diseases related to the brain and nervous system. However, no systematic study has explored the diversity and phylogenetic distribution of psychoactive plants. We compiled a database of 501 psychoactive plant species and their properties from published sources. We mapped these plant attributes on a phylogenetic tree of all land plant genera and showed that psychoactive properties are not randomly distributed on the phylogeny of land plants; instead certain plant lineages show overabundance of psychoactive properties. Furthermore, employing a ‘hot nodes’ approach to identify these lineages, we can narrow down our search for novel psychoactive plants to 8.5% of all plant genera for psychoactivity in general and 1–4% for specific categories of psychoactivity investigated. Our results showcase the potential of using a phylogenetic approach to bioprospect plants for psychoactivity and can serve as foundation for future investigations.

Bryophytes (including mosses, liverworts and hornworts) are a heterogeneous group of terrestrial plants, which comprise over 24,000 species worldwide. Given the various biological activities reported from bryophytes, they have a huge commercial potential. Due to their minute size and rather small biomass in various ecosystems, bryophytes are a seldom part of ethnomedicine and rarely subject to medicinal and chemical analyses. Still, hundreds of novel natural products have been isolated from bryophytes. Bryophytes have been shown to contain numerous potentially useful natural products, including polysaccharides, lipids, rare amino acids, terpenoids, phenylpropanoids, quinones and many other specialized metabolites. Additionally, different bryophyte extracts and isolated compounds have shown antimicrobial, antiviral, cytotoxic, nematocidal, insecticidal, effects on smooth and non-striated muscles, weight loss, plant growth regulators and allelopathic activities. Bryophytes also cause allergies and contact dermatitis. All these effects highlight bryophytes as potential source for herbal remedies and production of chemicals to be used in various products.

Selective use of crude plant extracts has been the oldest ritual in ancient Indian Medicinal System ‘Ayurveda’, as well as in Traditional Chinese Medicine system for thousands of years. This has been well documented that herbal medicines of Chinese, Indian, Korean and Native American people had included bryophytes, lichens, lycophytes and ferns. Since antiquity, most of the ferns and fern allies have given many health benefits to ancient civilizations who had used them for food, tea and drugs. Modern approaches have combined multidisciplinary technologies and have specific chemical compounds extracted and identified for producing very particulate medicines from plant parts. Plants, which yield appreciable quality and quantity of polysaccharides, steroids, terpenoids, flavonoids, alkaloids and antibiotics are suitable for dragging out drugs for many ailments/diseases, including cancer treatments. Modern explorations on the functional activities of pteridophytes for human health by discovering specific compounds and their usage in medicines have widened the scope of pteridophytes by shaping these plants as a great boon for pharmaceutical companies and related industries. Even ‘fern weeds’, which invade our freshwater bodies and reduce the freshwater wealth of a lake, e.g. Azolla, Salvinia, Marsilea, Ceratopteris, etc. can be utilized to produce life saving drugs because they are reservoirs of very many organic compounds that are useful as medicines. Some of the fern genera have a few unique secondary metabolites, which have not been discovered in higher plants. Polyphenols are useful phytochemicals, which provide health benefits such as antioxidants. From experiments on screening of total polyphenol contents of 37 ferns and fern allies, Polystichum lepidocaulon and Polystichum polyblepharum were reported to have more than 13% of total polyphenols from dried materials of both fronds and rhizomes. In addition, fronds of Davallia mariesii and rhizomes of Cyrtomium fortune, Dicranopteris pedata, Athyrium niponicum and Dryopteris nipponensis showed more than 10% of total polyphenols from dried materials. High bioactivities of traditional medicinal ferns have been studied internationally to underscore their roles in medicine. These attempts have confirmed various bioactivities, such as antioxidant, antimicrobial, antiviral, anti-inflammatory, antitumor and anti-HIV, etc. The occurrence of antibiotic activity in the extracts of more than 200 species of pteridophytes has been shown to be of prime significance within the period of 1975–2015. The active substances in many cases were found to be antibacterial to penicillin-resistant Staphylococcus aureus, Mycobacterium phlei, Salmonella typhi, Vibrio cholera, and Pseudomonas aeruginosa. Dryopteris cochleata was active against both bacteria and fungi. Five other species of Dryopteris showed remarkable antibacterial activity. The ferns of ‘Adiantum group’ have been found to be particularly active against Gram-positive bacteria. The polypodiaceous ferns constitute a rich group of which Microsorum alternifolium, Leptochillus decurrens, Polypodium irioides, Pyrrosia mannii and Phymatodes ebenipes deserve special mention. Several thelypteroid, davallioid and athyrioid ferns, in addition to antibiotic activity have also been found to show most useful bioactivity for our life – the antioxidant activity. The latter superb biochemical quality of ferns alone makes most ferns of great advantage to human health. Lycophytes particularly Lycopodium clavatum and Equisetum hyemale and ferns (Dryopteris and Adiantums) have had constituted the backbone of Homeopathic medicines and now many more genera have been added to the network of modern medicinal approaches in the drug industry. These pteridophytes are indispensably integral parts of forests world over. A few of the aquatic ferns (Azolla, Salvinia) serve as excellent bio-fertilizers and bioremediation agents. Medicinal plants are under cultivation and cultured world over. Botanically, say a thousand years ago, these were wild and many of them were weeds. As pteridophytes have survived since Paleozoic, they have undergone series of disruptive adaptive changes of environment than any other vascular plants. These plants most likely, could withstand the tests of geological time on account of their being guarded with genetic capability of possessing many useful oils, phytochemicals (secondary metabolites) such as flavonoids, steroids, alkaloids, phenols, triterpenoid compounds, varieties of amino acids and fatty acids, which in turn offer inherent tolerance and defense system . Additionally, from evolutionary point of view majority of ferns have constituted carpet flora and have worked as ‘cradles’ in natural forests so as to nurture small animals particularly reptiles and mammals. Ferns are denominators of prevalent rich biodiversity in almost every part of the earth. Comparison of evolutionary adaptations and natural innovations illuminate the genetic basis for the development of organisms. It is emphasized that there should be good field stations just in the peripheral region of reserved forests with large green houses to function as ‘Fernariums/ Mossariums/ and/or Lichenariums’ to conserve and maintain rare, endangered and medicinally superlative species found in those areas/forests. Gene networks (DNA stretches) that retain similar wiring diagrams (some or many similar DNA sequences) among related, distantly related or even totally diverse organisms point to the ways in which regulatory regions of the genome have evolved. Indisputably, comparative genomics can help us in deciphering evolvability of gene network and conservation modes during vast geological journey in evolution. We need exhaustive genomics and multidimensional molecular genetic studies on pteridophytes so as to discover unique DNA sequences, which could turn the gates of modern medicine.

With increasing interest in natural products of plant origin for medicinal and health care benefits there is added emphasis on the quality of the source raw material. In most cases the vegetative tissues and organs are the source of the required raw material. However, such tissues/organs may become infested/susceptible to many diseases causing deterioration of the quality of the desired economic product and loss of genetic resources. Considerable progress has been made with respect to the identification of disease causing organisms, and their pathogenic impact at organ, cellular and biochemical level. This review focuses on various diseases caused by bacteria, fungi, nematodes, viruses and phytoplasmas threatening the yield, biomass, bioactive potential of medicinal and aromatic plants of the sub-tropics. Several studies suggest that management of diseases through biological measures is more effective to check multiple diseases. Necessary management strategies for efficient disease management to realize quality raw material and enhanced metabolite productive potential have been outlined.

Medicinal plants are the vital source of numerous structurally diverse pharmacologically active metabolites collectively called as secondary metabolites finding extensive applications in traditional systems of medicine and in pharmaceutical industries. Several distinctive and complex pathways operate in an interactive manner via metabolic networks that are responsible for the accumulation of such highly specialized metabolites. Secondary metabolites are believed to play a wide spectrum of physiological and functional roles in plants, many of which being investigated and supported by the experimental studies. Biosynthetic pathway related studies on various aspects in these medicinal plants have been found very tedious owing to several issues in plants such as considerably lower metabolite concentrations in native tissues, existence at different locations, and highly complex multi-step pathways, etc. Pathway elucidation and gene/enzyme discovery for studying metabolic pathway evolution and subsequent engineering could be better achieved by mining various pathway databases and reconstruction of metabolic networks available at different omics databases. Though medicinal plants have a limited range of genomic sequences available, however recently, next generation sequencing is being widely used to generate a comprehensive transcriptomic resource for these plants. It is anticipated that databases and resources generated from these studies are likely to play a key role towards the study and exploitation of metabolites from medicinal plants in near future. In this review, we have discussed next generation sequencing approaches, which were used for the generation of transcriptomic resources for several medicinally important plants. The relevance of transcriptomic approaches in curation of the pathways linked with the synthesis of major secondary metabolites along with their precursors of pharmaceutical importance in medicinal plants is also comprehensively analysed.

Periwinkle [Catharanthus roseus (L) G. Don] has become one of the very extensively investigated medicinal plants after the discovery of two powerful anti-cancer alkaloids, vinblastine and vincristine, in its leaves more than 50 years ago. These alkaloidal drugs are still in clinical use. Also, periwinkle is still the only source of these alkaloids and their precursors, catharanthine and vindoline. Low concentrations of these alkaloids in the plant and, therefore, high costs of their extraction have led to tremendous efforts towards understanding their biosynthesis and exploration of alternate ways of their production such as, chemical synthesis, cell, tissue and hairy root cultures, and metabolic engineering of heterologous organisms. Literature on this plant is quite voluminous, with an average of about 80 publications per year during last three decades (1985–2015). Nearly 60% of these publications are on physiology, biochemistry, cell and tissue culture, phytochemistry, metabolic and genetic engineering aspects. In spite of these efforts, an economically viable alternative to field-grown periwinkle plants as a source of these alkaloids has not yet been found. Biosynthesis of C. roseus alkaloids is a complex process involving many genes, enzymes, regulators, inter- and intra-cellular transporters, cell types, organelles and tissues and its current understanding is still considered to be incomplete to produce C. roseus alkaloids through metabolic engineering/synthetic biology. Till such time, breeding periwinkle varieties with higher concentrations of anti-cancer alkaloids for cultivation can be an alternate approach to meet the demand for these alkaloids and reduce their costs. While literature on cell and tissue culture, phytochemistry, metabolic and genetic engineering aspects of periwinkle has been reviewed periodically, crop production and plant breeding aspects have received little attention. In this paper, an attempt has been made to bring together published information on genetics and breeding of periwinkle as a medicinal plant. Some probable constraints which may have hindered taking up periwinkle breeding are identified. Initially, quite a few attempts have been made at genetic improvement of periwinkle through induced polyploidy, and subsequently through induced mutagenesis. Mutations, both natural and induced, provide a valuable resource for use in breeding and in functional and reverse genomics research. It is only during last 6–7 years, genetic diversity has been assessed using molecular markers and very recently molecular markers have been identified for marker-assisted selection for alkaloid yield.

Mucuna pruriens (L.) DC is a tropical legume cover crop with promising nutritional and agronomic potentials. It is also a key source of 3,4 dihydroxy-L-phenylalanine (L-Dopa) – a precursor of dopamine used in the treatment of Parkinson's disease. However, lack of well-characterized germplasm plus poor accessibility to genomic resources has hindered its breeding programs. Furthermore, the cause and effect of various biotic and abiotic stresses impacting yield is also little studied. Systematic collection and evaluation of Indian germplasm by our group revealed presence of a diverse gene pool in India that can support a variety of breeding needs. The stability of L-Dopa trait across environments examined through Genotype and environment (G × E) interaction studies, as well as feasibility check on barcoding and phylogenetic analyses based on karyotype and conserved nuclear and chloroplast genes showed promising outcome. Germplasm screening for select biotic abiotic stresses identified resilient genotypes. Advances in use of DNA markers for diversity analysis, linkage map development, tagging of genes/quantitative trait loci for qualitative and quantitative traits, and progress in genomics are presented.