Development of highly discriminatory SCoT- and CBDP-based SCAR fingerprint for authentication of Indian senna (Senna alexandrina Mill.) formerly Cassia angustifolia Vahl.).

Introduction: Indian senna (Senna alexandrina Mill.) (formerly Cassia angustifolia Vahl.) is an important medicinal plant of the family Fabaceae. The leaves and pods of Indian senna yield sennosides and rhein-based laxative. Adulteration of Indian senna is a serious issue as with most of the medicinal plants used in the Indian systems of traditional medicine. The bulk of dried leaves and pods of morphologically related species, such as Cassia fistula, Senna occidentalis, Senna sophera, and Senna tora, is usually mixed with those of the Indian senna, and the admixture is used in laxative-based formulations. The present investigation is a modest attempt at developing species-specific start codon targeted (SCoT) polymorphism- and CAAT-box-derived polymorphism (CBDP)-based sequence-characterized amplified region (SCAR) markers for the identification and authentication of Indian senna and four adulterant species (C. fistula, S. occidentalis, S. sophera, and S. tora species). Methods: In this study, genomic DNA extracted from 44 accessions of Indian senna and four adulterant species was subjected to SCoT and CBDP PCR. The polymorphic amplicons were identified, eluted, ligated, and transformed into Escherichia coli DH5 α strain. PCR, restriction analysis, and DNA sequencing confirmed the transformed recombinant plasmid clones. Results: Post-sequencing, the sequence of the primary SCoT and CBDP primers was analyzed and extended into the unique signature sequence of the concerned accessions. This resulted in development of one SCoT-44- and two CBDP-25-based SCARs. SCoT-44 SCAR produced a signature amplicon of 287 bp for accession DCA120, and CBDP-25 SCAR yielded signature amplicons of 575 and 345 bp for accessions DCA13 and DCA119, respectively. The developed SCAR markers were validated across 48 samples (44 accessions of Indian senna and 4 adulterant species) and produced distinct amplicons in Indian senna only, while no such amplicon was observed in the other four adulterant species. Discussion: The information generated using these markers have been faithfully converted to single-locus, unequivocal, highly reproducible, and informative sequence-based SCAR markers. These markers will enable discrimination of individual plants on the basis of unique sequence-specific amplicons, which could be used as diagnostic markers to settle issues pertaining to the true identity of Indian senna.

Lignans from linseed (Linum usitatissimum L.) and its allied species: Retrospect, introspect and prospect.

Lignans are complex diphenolic compounds representing phytoestrogens and occur widely across the plant kingdom. Formed by the coupling of two coniferyl alcohol residues, lignans constitute major plant "specialized metabolites" with exceptional biological attributes that aid in plant defence and provide health benefits in humans by reducing the risk of ailments such as cancer, diabetes etc. Linseed (Linum usitatissimum L.) is one of the richest sources of lignans followed by cereals and legumes. Among the various types of lignans, secoisolariciresinol diglucoside (SDG) is considered as the essential and nutrient rich lignan in linseed. Lignans exhibit established antimitotic, antiviral and anti-tumor properties that contribute to their medicinal value. The present review seeks to provide a holistic view of research in the past and present times revolving around lignans from linseed and its allied species. This review attempts to elucidate sources, structures and functional properties of lignans, along with detailed biosynthetic mechanisms operating in plants. It summarizes various methods for the determination of lignan content in plants. Biotechnological interventions (in planta and in vitro) aimed at enriching lignan content and adoption of integrative approaches that might further enhance lignan content and medicinal and nutraceutical value of Linum spp. have also been discussed.

Post-transcriptional gene silencing: Basic concepts and applications.

Post-transcriptional gene silencing (PTGS)-mediated gene silencing exploits the cellular mechanism wherein transcripts having sequence similarity to the double-stranded RNA (dsRNA) molecules present in the cell will be subjected to degradation. PTGS is closely related to natural processes such as RNA-mediated virus resistance and cross-protection in plants. Gene silencing and the cellular machinery for affecting this phenomenon might have evolved as a natural protective measure against viral infection in plants. In PTGS, small interfering RNA (siRNA) molecules of 21-23 nucleotides length act as homology guides for triggering the systemic degradation of transcripts homologous to the siRNA molecules. PTGS phenomenon, first discovered in transgenic petunia plants harbouring chalcone synthase gene and termed co-suppression, has been subsequently exploited to target specific gene transcripts for degradation leading to manifestation of desirable traits in crop plants. Targeted gene silencing has been achieved either through the introduction of DNA constructs encoding dsRNA or antisense RNA or by deploying cosuppression constructs producing siRNAs against the transcript of interest. Understanding the mechanism of gene silencing has led to the development of several alternative strategies for inducing gene silencing in a precise and controlled way. This has paved the way for using PTGS as one ofthe chief functional genomicstools in plants and has helped in unraveling the mechanism of many cellular processes and identifying the focal points in pathways, besides, opening new vistas in genetic engineering of plants for human benefits. PTGS has shown great potential in silencing the deleterious genes efficiently so that value-added plant products could be obtained. Thus, PTGS has ushered in a new era in the genetic manipulation of plants for both applied and basic studies. In this review, we have outlined the basics of RNAi-mediated gene silencing and summarized the work carried out at our institute using this approach, as case studies. In particular, adopting RNAi-mediated gene silencing (a) as a method to restore fertility in transgenic male sterile lines developed based on orfH522 gene from sunflower PET1-CMS source, (b) as a tool to suppress the production of toxic proteins, ricin and RCA, in castor, and (c) as an approach to induce bud necrosis virus resistance in sunflower has been discussed. Examples from other plant systems also have been mentioned to exemplify the concept and utility of gene silencing in crop plants.

Metal catalyst free cyclization of 3-alkynyl substituted 2-(indol-3-yl)quinoxalines in TFA alone: a new synthesis of indolophenazines.

TFA alone was found to be remarkably effective for the intramolecular hydroarylation (IMHA) of alkynes when employed as a solvent in the cyclization of 3-alkynyl substituted 2-(indol-3-yl)quinoxalines. This simple and metal free cyclization method afforded a range of indolophenazines as new and potential cytotoxic agents. The use of excess TFA was found to be crucial for the success of this reaction.

TFAA/H3PO4 mediated unprecedented N-acylation of carbazoles leading to small molecules possessing anti-proliferative activities against cancer cells.

For the first time TFAA/H3PO4 has facilitated the direct and metal-free N-acylation of carbazoles leading to a number of N-acylated derivatives. Several of these compounds were found to be promising when tested for their anti-proliferative properties against oral cancer cell lines.