Significance: Organisms from bacterial spores, plant seeds, and invertebrate cysts to diapausing insects and mammalian hibernators dramatically suppress metabolism to save energy during dormant periods. Understanding regulatory mechanisms controlling metabolic depression provides insights into fundamental control of energy use during dormancy and offers perspectives that may allow artificial induction and breaking of dormancy. Some insects and mammalian hibernators show periodic arousal from metabolic depression during dormancy. We show that insects follow similar metabolic tactics during torpor and periodic arousal as mammalian hibernators, characterized by anaerobic metabolism during depression and aerobic metabolism during arousal, emphasizing fundamental similarities in metabolic regulation. Physiological levels of ROS regulate the switch from metabolic depression to periodic arousal thereby controlling substrate flow into the tricarboxylic acid cycle.

Secondary metabolites are essential components for the survival of plants. Secondary metabolites in complex mixtures from plants have been adopted and documented by different traditional medicinal systems worldwide for the treatment of various human diseases. The extraction strategies are the key components for therapeutic development from natural sources. Polarity-dependent solvent-selective extraction, acidic and basic solution-based extraction, and microwave- and ultrasound-assisted extraction are some of the most important strategies for the extraction of natural products from plants. The method needs to be optimized to isolate a specific class of compounds. Therefore, to establish the mechanism of action, the characterization of the secondary metabolites, in a mixture or in their pure forms, is equally important. LC-MS, GC-MS, and extensive NMR spectroscopic strategies are established techniques for the profiling of metabolites in crude extracts. Various protocols for the extraction and characterization of a wide range of classes of compounds have been developed by various research groups and are described in this review. Additionally, the possible means of characterizing the compounds in the mixture and their uniqueness are also discussed. Hyphenated techniques are crucial for profiling because of their ability to analyze a vast range of compounds. In contrast, inherent chemical shifts make NMR an indispensable tool for structure elucidation in complex mixtures.

A metal-free one-pot approach to the diversity oriented synthesis of N-heterocycles, 1,2,4-oxadiazoles and 2,6 disubstituted pyrimidin-4-ones is described via carboxamidation of amidines with aryl carboxylic acids and aryl propargylic acids. The reactions occur at room temperature forming N-acylamidines which undergo tandem nucleophilic addition–deamination–intramolecular cyclisation to give the corresponding heterocyclic compounds in good to excellent yields. This one pot approach has led to the successful synthesis of the drug lead molecule, ataluren, 3-(5-(2-fluorophenyl)-1,2,4-oxadiazol-3-yl) benzoic acid in two steps.