Ratnamala S. Bendre

Natural products – antifungal agents derived from plants

A new spectrum of human fungal infections is increasing due to increased cancer, AIDS, and immunocompromised patients. The increased use of antifungal agents also resulted in the development of resistance to the present drugs. It makes necessary to discover new classes of antifungal compounds to cure fungal infections. Plants are rich source of bioactive secondary metabolites of wide variety such as tannins, terpenoids, saponins, alkaloids, flavonoids, and other compounds, reported to have in vitro antifungal properties. Since the plant kingdom provides a useful source of lead compounds of novel structure, a wide-scale investigation of species from the tropics has been considered. Therefore, the research on natural products and compounds derived from natural products has accelerated in recent years due to their importance in drug discovery. A series of molecules with antifungal activity against different strains of fungus have been found in plants, which are of great importance to humans. These molecules may be used directly or considered as a precursor for developing better molecules. This review attempts to summarize the current status of important antifungal compounds from plants.

Highly selective turn-on fluorescent sensor for nanomolar detection of biologically important Zn2+ based on isonicotinohydrazide derivative: application in cellular imaging.

A new Zn(2+) selective chemosensor (3) was synthesized by condensation of commercially available substituted salicylaldehyde and isonicotinohydrazide, and characterized by single crystal X-ray crystallography. Receptor 3 with Zn(2+) exhibited a highly selective and pronounced enhancement in the fluorescence emission among different cations by forming a 2:1 complex. The receptor can detect Zn(2+) up to nanomolar level (6.75 nM) with good tolerance of other metal ions and can be used for in vitro cellular imaging.

2,2′-(Hydrazine-1,2-diylidenedimethylylidene)bis(6-isopropyl-3-methylphenol) based selective dual-channel chemosensor for Cu2+ in semi-aqueous media

A novel receptor based on a substituted salicylaldehyde derivative, 2,2′-(hydrazine-1,2-diylidenedimethylylidene)bis(6-isopropyl-3-methylphenol) (1), was synthesized and characterized using various spectroscopic techniques. The UV-visible spectroscopic studies of the receptor showed selectivity for Cu2+ in the presence of other metal ions by a change in colour from colourless to yellow. A red shift was observed with the appearance of a new absorption band at 450 nm in CH3OH–H2O (60 : 40 v/v). Fluorescence studies of the receptor showed “turn-off” recognition properties for the Cu2+ ion with a 1 : 1 binding stoichiometry and the detection limit was 50 nM.

A highly selective fluorescent ‘turn-on’ chemosensor for Hg2+ based on a phthalazin-hydrazone derivative and its application in human cervical cancer cell imaging

A new phthalazin-hydrazone based fluorescent chemosensor (E)-5-(diethylamino)-2-((2-(phthalazin-1-yl)hydrazono)methyl)phenol (1) was reported. Sensor 1 showed a high selectivity and sensitivity towards Hg2+ by giving significant fluorescence enhancement at 550 nm over other tested cations in DMSO/H2O (80 : 20, v/v) medium. The association constant was 1.0 × 104 M−1 between sensor 1 and Hg2+. Sensor 1 showed a nanomolar detection limit of 26.1 nM Hg2+. Finally, the fluorescence imaging experiments for the detection of intracellular Hg2+ in human cervical cancer HeLa cells showed its practical utility in biological samples.

Hybrid molecules of carvacrol and benzoyl urea/thiourea with potential applications in agriculture and medicine

Benzoyl phenyl urea, a class of insect growth regulators acts by inhibiting chitin synthesis. Carvacrol, a naturally occurring monoterpenoid is an effective antifungal agent. We have structurally modified carvacrol (2-methyl-5-[1-methylethyl] phenol) by introducing benzoylphenyl urea linkage. Two series of benzoylcarvacryl thiourea (BCTU, 4a-f) and benzoylcarvacryl urea (BCU, 5a-f) derivatives were prepared and characterized by elemental analysis, IR, (1)H and (13)C NMR and Mass spectroscopy. Derivatives 4b, 4d, 4e, 4f and 5d, 5f showed comparable insecticidal activity with the standard BPU lufenuron against Dysdercus koenigii. BCTU derivatives 4c, 4e and BCU 5c showed good antifungal activity against phytopathogenic fungi viz. Magnaporthe grisae, Fusarium oxysporum, Dreschlera oryzae; food spoilage yeasts viz. Debaromyces hansenii, Pichia membranifaciens; and human pathogens viz. Candida albicans and Cryptococcus neoformans. Compounds 5d, 5e and 5f showed potent activity against human pathogens. Moderate and selective activity was observed for other compounds. All the synthesized compounds were non-haemolytic. These compounds have potential application in agriculture and medicine.

Novel fluorescent chemosensing of CN− anions with nanomolar detection using the Zn2+–isonicotinohydrazide metal complex

A novel chemosensor based on the Zn2+–isonicotinohydrazide complex ‘(ZnL)’ was developed for the selective detection of cyanide (CN−) over other tested anions, such as HSO4−, F−, Cl−, Br−, I−, NO3−, PO43−, SO42−, SCN−, S2−, CH3COO− and H2PO4− in 80% MeOH (organic–aqueous medium). The detection of CN− with (ZnL) could be possible with both UV-visible and fluorescence responses without any interference effects from other anions. This system shows excellent sensitivity with a lower detection limit of 5.49 nM.

Outlooks on Medicinal Properties of Eugenol and its Synthetic Derivatives

Eugenol is found in essential oils of many plants. It belongs to a class of naturally occurring phenolic monoterpenoids, chemically it is an allyl chain-substituted guaiacol. Eugenol is a member of the phenylpropanoids class and is remarkably versatile molecule incorporated as a functional ingredient in several products and has found applications in the pharmaceutical, agricultural, fragrance, flavor, cosmetic and various other industries. Its vast range of pharmacological activities has been well-researched which include antimicrobial, anti-inflammatory, analgesic, antioxidant and anticancer activities. In present review we shortly summarize medicinal properties of Eugenol and its derivatives.

Design, synthesis and biological activities of novel 5-isopropyl-2-methylphenolhydrazide-based sulfonamide derivatives

Sulfonamides have enormous importance in biological sciences. In the present investigation, the fundamental energetic group, hydrazide-based sulfonamide, has been incorporated into a naturally occurring phenolic monoterpenoid, carvacrol (5-isopropyl-2-methylphenol) moiety, with the aim of combining the active groups in order to generate more potent antimicrobial and anti-oxidant agents. Series of hydrazide-based sulfonamide derivatives (IV a–g) have been synthesized and characterized by modern sophisticated techniques such as 1H NMR, 13C NMR and LC–MS. The newly synthesized derivatives were screened for their antimicrobial activities against three fungal (Aspergillus niger, A. flavus and A. fumigatus) and three bacterial (Escherichia coli, Staphylococcus aureus and Bacillus subtilis) species, of which compounds IVc and IVd were found to have good antifungal activity and compounds IVd and IVg exhibited decent antibacterial activities. antioxidant activity was performed by DPPH radical scavenging assay. Compound IVd has been found to be more active in comparison to standard ascorbic acid and compounds IVa, IVb, and IVc demonstrated excellent antioxidant activity.Graphical Abstract

Design, Synthesis and Biological Evaluation of Novel Class DiindolylMethanes (DIMs) Derived from Naturally Occurring PhenolicMonoterpenoids

Several Diindolyl alkanes and their derivatives have been isolated from plant and marine sources. Among the various derivatives of indoles, Diindolyl methanes have wide medicinal applications such as to induce apoptosis in human cancer cells, antibacterial, Anti-inflammatory, antiviral and hormonal control activities. Therefore, they play essential role in marine as well as terrestrial living systems. In present studies we report novel class of Diindolyl methanes prepared from natural phenolic monoterpenoids, via ortho formylation of phenolic monoterpenoids (Carvacrol, Thymol and Eugenol), followed by synthesis, characterization, anticancer, antioxidant and α-amylase inhibitory activities. All the synthesized derivatives show moderate anticancer activities against human breast cell line MCF7, good antioxidant and α-amylase inhibitory activities using DPPH and α-amylase assay respectively.

Pyrrole‐coupled salicylimine‐based fluorescence “turn on” probe for highly selective recognition of Zn2+ ions in mixed aqueous media: Application in living cell imaging

Cation sensing behaviour of a pyrrole‐based derivative (2‐hydroxyl 3 methyl 6 isopropyl benzaldehyde}‐3,4‐dimethyl‐1H‐pyrrole‐2‐carbohydrazide (receptor 3) has been explored and is found to be selective towards Zn2+ over a variety of tested cations. The receptor 3 has shown high selectivity and sensitivity towards Zn2+ over the other alkali, alkaline earth and transition metal ions. In the presence of Zn2+, absorption band of receptor 3 has shown the red shift. The sensing behaviour has been suggested to continue via enhancement process which has further been supported by UV‐vis absorption and theoretical density functional theory (DFT) calculations indicating the formation of a 1:1 complex between the pyrrole based receptor 3 and Zn2+. The present work is presenting a highly selective dual channel colorimetric sensor for zinc with great sensitivity. The developed sensor was successfully applied to image intracellular Zn2+ in living cells. Copyright