Rajiv Roy

Stevioside and Related Compounds – Molecules of Pharmaceutical Promise: A Critical Overview

Stevioside, an ent‐kaurene type of diterpenoid glycoside, is a natural sweetener extracted from leaves of Stevia rebaudiana (Bertoni) Bertoni. Stevioside and a few related compounds are regarded as the most common active principles of the plant. Such phytochemicals have not only been established as non‐caloric sweeteners, but reported to exhibit some other pharmacological activities also. In this article, natural distribution of stevioside and related compounds, their structural features, plausible biosynthetic pathways along with an insight into the structure–sweetness relationship are presented. Besides, the pharmacokinetics, wide‐range of pharmacological potentials, safety evaluation and clinical trials of these ent‐kaurene glycosides are revisited.

Argemone mexicana: chemical and pharmacological aspects

The Papaveraceae, informally known as the poppy family, are an ethnopharmacologically important family of 44 genera and approximately 760 species of flowering plants. The present work offers a review addressing the detailed chemistry and pharmacology of Argemone mexicana L. regarded as one of the most significant plant species in traditional system of medicine. The plant is used in different parts of the world for the treatment of several ailments including tumors, warts, skin diseases, inflammations, rheumatism, jaundice, leprosy, microbial infections, and malaria. Interestingly, the plant is the source of a diverse kind of chemical constituents although alkaloids are mostly abundant. Beyond pharmaceutical efficacies, certain plant parts also show toxic effects as well. Hence, an up-to-date information on the chemical and pharmacological knowledge on this plant may be helpful to guide researchers anticipating to undertake further investigations in these directions. The present review covers literature up to 2012 and enlists 111 references.

Sunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum Linn. with enhanced antibacterial activity

Background Nanotechnology is now regarded as a distinct field of research in modern science and technology with multifaceted areas including biomedical applications. Among the various approaches currently available for the generation of metallic nanoparticles, biogenic synthesis is of increasing demand for the purpose of green nanotechnology. Among various natural sources, plant materials are the most readily available template-directing matrix offering cost-effectiveness, eco-friendliness, and easy handling. Moreover, the inherent pharmacological potentials of these medicinal plant extracts offer added biomedical implementations of the synthesized metal nanoparticles. Results A robust practical method for eco-friendly synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum (Tulsi) as both reducing and capping agent, under the influence of direct sunlight has been developed without applying any other chemical additives. The nanoparticles were characterized with the help of UV-visible spectrophotometer and transmission electron microscopy (TEM). The prepared silver nanoparticles exhibited considerable antibacterial activity. The effects were more pronounced on non-endospore-forming Gram-positive bacteria viz., Staphylococcus aureus, Staphylococcus epidermidis, and Listeria monocytogenes than endospore-forming species Bacillus subtilis. The nanoparticles also showed prominent activity on Gram-negative human pathogenic Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and plant pathogenic Pantoea ananatis. A bactericidal mode of action was observed for both Gram-positive and Gram-negative bacteria by the nanoparticles. Conclusions We have developed a very simple, efficient, and practical method for the synthesis of silver nanoparticles using aqueous leaf extract of O. sanctum under the influence of direct sunlight. The biosynthesis of silver nanoparticles making use of such a traditionally important medicinal plant without applying any other chemical additives, thus offers a cost-effective and environmentally benign route for their large-scale commercial production. The nanoparticles dispersed in the mother solution showed promising antibacterial efficacy.Graphical Abstract Sunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum Linn. with enhanced antibacterial activity. Electronic supplementary material The online version of this article (doi:10.1186/s13588-014-0018-6) contains supplementary material, which is available to authorized users.

Evaluation of the Antimicrobial Potential of Two Flavonoids Isolated from Limnophila Plants

The antimicrobial potential of two bioflavonoids, i.e., 5,7‐dihydroxy‐4′,6,8‐trimethoxyflavone (1) and 5,6‐dihydroxy‐4′,7,8‐trimethoxyflavone (2), isolated from Limnophila heterophylla Benth. and L. indica (Linn.) Druce (Scrophulariaceae), respectively, were evaluated against the microbial strains Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Alternaria solani, and Candida albicans. Compounds 1 and 2 exhibited moderate but broad antimicrobial activities against both Gram‐positive and Gram‐negative bacteria and also against the fungal pathogens. Moreover, the mechanism of action of 1 and 2 on the cellular functions or structures of some of the microorganisms was studied. Compound 1 showed a bactericidal effect against E. coli and S. aureus (MICs of 200 and 250 μg/ml, resp.), while compound 2 was found to effectively kill B. subtilis by cell lysis. The growth of A. solani and C. albicans was inhibited by compounds 1 and 2, respectively. The effects of the flavonoids on the cellular structures and the carbohydrate metabolic pathways were studied by scanning electron microscopy (SEM) of the treated cells and by assessing the specific activity of key enzymes of the pathways, respectively. At sublethal doses, they enhanced the activity of gluconeogenic fructose bisphosphatase, but decreased the activity of phosphofructokinase and isocitrate dehydrogenase, the key enzymes of the EmbdenMeyerhofParnas pathway and the tricarboxylic acid cycle, respectively.

A new pentacyclic triterpene with potent antibacterial activity from Limnophila indica Linn. (Druce)

A new pentacyclic triterpenoid constituent, characterized as 3-oxo-olean-12(13),18(19)-dien-29α-carboxylic acid (1) on the basis of detailed spectral studies, was isolated from the aerial parts and roots of Limnophila indica (Scrophulariaceae). Compound 1 exhibited considerable antibacterial activity against three Gram-positive bacteria viz. Bacillus subtilis, Staphylococcus aureus and Listeria monocytogenes (MICs within a range of 25-30 μg/ml) and moderate activity against four Gram-negative bacteria Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and Pantoea ananatis (MICs within a range of 30-100 μg/ml). The plant pathogenic bacterium P. ananatis and human pathogenic S. typhimurium responded at comparatively higher concentrations of the compound 1, which were 75 and 100 μg/ml respectively. The compound inhibited the growth of Gram-positive B. subtilis and Gram-negative P. aeruginosa completely with a clear bactericidal mode of action at their MIC values. The compound upon treatment on both B. subtilis and P. aeruginosa released substantial amount of nucleic acid in the external medium and also effected the change of morphology towards pleomorphicity, thereby indicating its probable action on cell membrane. Furthermore, the triterpenoid 1 was found not to inhibit a probiotic lactic acid bacterium Lactococcus lactis subsp. lactis LABW4 under in vitro condition and to possess no toxicity in Swiss albino mice.

A new long-chain secondary alkanediol from the flowers of Argemone mexicana

An ethanolic extract of the dried flower petals of Argemone mexicana afforded a new and optically active secondary C31-alkanediol characterised as hentriacontane-3,20-diol on the basis of spectroscopic studies including IR, HRMS, 1H and 13C NMR.

A comparative antibacterial evaluation of raw and processed Guñjā (Abrus precatorius Linn.) seeds

Background: Seed of Guñjā (Abrus precatorius Linn.), a known poisonous drug, is used extensively in various ayurvedic formulations with great therapeutic significance. Ayurveda recommends the administration of Guñjā in diseases like Indralupta (alopecia), Śotha (edema), Kṛmi (helminthes), Kuṣṭha (skin diseases), Kaṇḍu (itching), Prameha (urinary disorders) etc., after being treated with specific Śodhana (purification) procedures. Objective: To assess the antimicrobial action of of raw and Śhodhita (Processed) Guñjā seeds Methods: Guñjā seeds after being processed with Godugdha (cows milk), Nimbu swarasa (Lemon juice), Kāñjī (Sour gruel) and water, as the media, were evaluated for its antibacterial effect against clinically important bacterial strains using agar well diffusion method. Results: Aqueous extracts of raw seeds of Guñjā exert its antibacterial effect on both Gram positive, as well as Gram negative bacteria but none of the Śodhita Guñjā seeds showed any bactericidal effect on any bacterial strains. Chloroform extracts of all the Śodhita Guñjā seed extracts could inhibit bacterial growth but with variations Conclusion: The study displayed that chloroform extracts of raw and śodhita samples for bacterial study were much sensitive than the aqueous extracts.