Abstract
A series of 4-aryl-hexahydroquinolines were prepared by Hantzsch reaction using aromatic aldehydes obtained from lignin, 1,3-cyclohexanediones, β-ketoesters and ammonium carbonate. The antioxidant properties of compounds 5a-c and 5g-i were evaluated by two methods: scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and scavenging effect on 2,2′-azino-bis(3-ethylenzothiazoline-sulfonic acid) diammonium salt (ABTS + ) radical. The results show that the compounds containing a methoxy moiety exhibit good activities. The study suggests that some synthesized compounds may serve as promising leads for the treatment against tumors or other free radical-related diseases.
Highlights
Free radicals play an important role in a number of biological processes, some of which are necessary for life, such as the intracellular killing of bacteria by phagocytic cells,[1] but excessive amounts of free radicals can lead to damage to biomolecules such as lipids, proteins, enzymes, and DNA in cells and tissues,[2] which may result in cancer, diabetes, cardiovascular diseases, autoimmune diseases, myocardial infarction, neurodegenerative disorders, aging, and other variety of diseases because of their excellent reactivity.[3,4,5]
The synthesis of polyhydroquinolines with vanillin and syringaldehyde as starting materials is expected to afford better antioxidant properties. Starting from these considerations, we report the synthesis and in vitro antioxidant properties of 4-aryl-hexahydroquinolines using the aromatic aldehydes from lignin via an efficient, catalyst-free, and four-component MCR Hantzsch reaction under microwave irradiation
A series of novel 4-aryl-hexahydroquinolines were obtained from lignin with a very environmentally benign procedure in good to excellent yields
Summary
Free radicals play an important role in a number of biological processes, some of which are necessary for life, such as the intracellular killing of bacteria by phagocytic cells,[1] but excessive amounts of free radicals can lead to damage to biomolecules such as lipids, proteins, enzymes, and DNA in cells and tissues,[2] which may result in cancer, diabetes, cardiovascular diseases, autoimmune diseases, myocardial infarction, neurodegenerative disorders, aging, and other variety of diseases because of their excellent reactivity.[3,4,5] The antioxidants can minimize or inhibit the oxidative damage through interrupting the free-radical formation or terminating the. The synthesis and antioxidant evaluation of new polyhydroquinolines, is included as part of our medicinal chemistry project aiming to identify a new class of antioxidants It is well-known that lots of natural and synthesized antioxidants possessing phenolic hydroxyl groups can improve their antioxidant activities by reacting with free radicals.[17] Vanillin and syringaldehyde, two phenolic hydroxyl containing compounds obtained from lignin, are widely used as additives in food, pharmaceutical and cosmetic industries due to their antioxidant activity besides the fragrant odor and non-toxicity.[18,19,20] The synthesis of polyhydroquinolines with vanillin and syringaldehyde as starting materials is expected to afford better antioxidant properties. Starting from these considerations, we report the synthesis and in vitro antioxidant properties of 4-aryl-hexahydroquinolines using the aromatic aldehydes from lignin via an efficient, catalyst-free, and four-component MCR (multi-component-reactions) Hantzsch reaction under microwave irradiation
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