Azomethine based nano-chemicals: Development, in vitro and in vivo fungicidal evaluation against Sclerotium rolfsii, Rhizoctonia bataticola and Rhizoctonia solani Prithusayak Mondal a , Rajesh Kumar a,⇑ , Robin Gogoi b a Division of Agricultural Chemicals, ICAR - Indian Agricultural Research Institute, New Delhi 110 012, India b Division of Plant Pathology, ICAR - Indian Agricultural Research Institute, New Delhi 110 012, India article info Article history: Received 3 June 2016 Revised 26 November 2016 Accepted 17 December 2016 Available online 24 December 2016 Keywords: Schiff base Nanotechnology Nano-formulation PEG Antifungal agent abstract Fungal diseases posing a severe threat to the production of pulses, a major protein source, necessitates the need of new highly efficient antifungal agents. The present study was aimed to develop azomethine based nano-fungicides for protecting the crop from fungal pathogens and subsequent yield losses. The protocol for the formation of nano-azomethines was generated and standardized. Technically pure azomethines were transformed into their nano-forms exploiting polyethylene glycol as the surface stabi- lizer. Characterization was performed by optical (imaging) probe (Zetasizer) and electron probe (TEM) characterization techniques. The mean particle sizes of all nano-fungicides were below 100 nm. In vitro fungicidal potential of nano-chemicals was increased by 2 times in comparison to that of conventional sized azomethines against pathogenic fungi, namely, Rhizoctonia solani, Rhizoctonia bataticola and Sclerotium rolfsii. The performance of nano-chemicals in pot experiment study was also superior to con- ventional ones as antifungal agent. Ó 2016 Elsevier Inc. All rights reserved. 1. Introduction Pulses being a great source of vegetarian protein of high biolog- ical value add a perfect accompaniment to most of the Indian meals when supplemented with cereals. In India, pulses have been reported as a ‘‘poor man’s meat and rich man’s vegetable”. With around 25% share in the global pulse production, India is the lar- gest producer in the world [1,2]. The mung bean (Vigna radiata), alternatively known as green gram, is one of them. Many food crops including grains, pulses and oilseeds and other crops of eco- nomic importance suffer from 20% or more yield reduction by var- ious phyto-pathogenic fungi. These fungi infect crops at any stage from seed sowing to harvesting of mature plants in the field result- ing in wilt, collar rot, damping-off, stem canker, dry root rot dis- eases [3]. Out of them, Sclerotium rolfsii, Rhizoctonia bataticola and Rhizoctonia solani are the major ones that attack mung bean. Synthetic pesticides which are being administered to control these pathogens pose a threat to the non-target organisms including mammals [4–6]. So, scientists are looking for new agrochemicals because target organisms are rapidly developing resistance to fungicides in current use. In search of novel fungicides with low environmental hazard or toxicity, low production cost, better selectivity and efficacy than the currently available or commercial formulations, azomethines have been synthesized for human benefits and improvement of farming systems owing to their multifaceted activities such as cytotoxicity, anticancer, antitumor, antifungal, antibacterial, herbi- cidal activity, and being building blocks for pesticide molecules [7– 12]. The current age is of nanotechnology that deals with various kinds of nanoparticles with diverse applications in different areas [13–34]. Biologically important nanoparticles are usually 1– 100 nm in any one of the dimensions [13–23]. Nano-sizing of the existing pesticides have more potential than its conventional or presently available formulations for controlling pests and subse- quently will be required in lesser quantity as compared to conven- tional pesticides causing less contamination to the soil and environment [19–34]. We have reported several azomethines as potent fungicides [8]. Out of those, six best potent fungicidal compounds were chosen for http://dx.doi.org/10.1016/j.bioorg.2016.12.006 0045-2068/Ó 2016 Elsevier Inc. All rights reserved. Abbreviations: Conv, conventional; PEG, polyethylene glycol; CU, control uninoculated; CI, control inoculated; N1-6, nano forms of azomethines 16; HEX, hexaconazole; ITCC, Indian type culture collection. ⇑ Corresponding author. E-mail address: rkb1973@gmail.com (R. Kumar). Bioorganic Chemistry 70 (2017) 153–162 Contents lists available at ScienceDirect Bioorganic Chemistry journal homepage: www.elsevier.com/locate/bioorg