Synthesis and Evaluation of 1H-1, 3-Benzimidazole Derivatives as Potential Antidiabetic and Antioxidant Agents

Benzimidazole as an Antidiabetic Agent: Benzimidazole is a privileged heterocyclic scaffold with broad therapeutic applications, including potent Antidiabetic activity.¹ Several Benzimidazole derivatives have shown significant hypoglycemic effects through multiple mechanisms:

• Glucokinase (GK) activation: Enhances hepatic glucose uptake and insulin secretion.α-Glucosidase inhibition: Delays carbohydrate digestion and glucose absorption, lowering postprandial blood glucose. ^2-3
• Glycosidase targeting: Inhibits key enzymes involved in carbohydrate metabolism. Improved glucose tolerance: Benzimidazole compounds have demonstrated antihyperglycemic effects in in vivo models (e.g., starch-induced hyperglycemia in rats). The structural flexibility of Benzimidazole allows substitutions at key positions (N1, C2, C5, C6), which can modulate biological activity and selectivity. Its antioxidant properties also help mitigate oxidative stress, a major contributor to diabetic complications. These characteristics make Benzimidazole derivatives promising candidates for developing novel Antidiabetic therapies. ^4-6

Figure no. 01: Structure and Nature of Benzimidazole.

Figure no. 02: Structure-based chemical activity of Benzimidazole

Figure no. 03: Biological activity and Mode of action for antioxidant properties of Benzimidazole.

Figure no. 04: Oxidative stress–mediated pathogenesis of diabetic neuropathy induced by hyperglycemia and Mechanism of action of Antidiabetic drugs

MATERIALS AND METHODS: ^7-10

Materials: All reagents and chemicals used in this study were of analytical grade and utilized without further purification. O-Phenylenediamine (98%), sodium hydroxide (NaOH, 98%), formic acid (HCOOH, 90%), and zinc acetate dihydrate (Zn (CH?COO) ?·2H?O, 98%) were procured from Loba Chemie Pvt. Ltd., Mumbai, India. Additional reagents included oxalic acid dihydrate (99%), acetic acid (90%), acetyl chloride (90%), benzoyl chloride (90%), and thioglycolic acid (98%). Other materials used were potassium permanganate (KMnO?, 99%), para-amino benzoic acid (PABA, 98%), general carboxylic acids (≥90%), salicylic acid (99%), cinnamic acid (98%), and benzoic acid (99%). Ethanol (EtOH, 99%), ammonium chloride (NH?Cl, 99%), and DPPH (2, 2-diphenyl-1-picrylhydrazyl, 98%) were also obtained from Loba Chemie. All solvents and reagents were used as received.

Procedure: Microwave-assisted organic synthesis (MAOS) was employed for the preparation of Benzimidazole derivatives. All reactions were carried out in standard borosilicate round-bottom flasks, and irradiations were performed in a domestic microwave oven at 595 W. Reaction progress was monitored visually and by precipitation behavior upon basification. Crude products were filtered, washed with ice-cold water, and purified by recrystallization from distilled water in the presence of a pinch of decolorizing charcoal.

Synthesis of Benzimidazole Derivatives: Synthesis of 4-(2, 3-dihydro-1H-1,3-benzodiazole-2-yl) aniline: A mixture of O-Phenylenediamine (8.1 g) and para-amino benzoic acid (4.8 g) was taken in a round-bottom flask, and phosphoric acid (1 mL) was added as a catalyst. The reaction mixture was subjected to microwave irradiation at 595 W for 7 minutes. After completion, the mixture was cooled to room temperature and neutralized with 10% NaOH solution until a slightly alkaline pH was achieved. The resulting precipitate was filtered, washed thoroughly with ice-cold water, and recrystallized from distilled water using a small quantity of activated charcoal. The purified product was dried and preserved for further synthesis.

Figure no. 05: Synthesis of 4-(2, 3-dihydro-1H-1, 3-benzodiazole-2-yl) aniline by treating it with PABA in presence of Phosphoric acid

Synthesis of N-formyl-4-(1H-benzimidazole-2-yl) Benzenamide: To a clean round-bottom flask, 4-(2, 3-dihydro-1H-1, 3-benzodiazole-2-yl) aniline (8.1 g) was added along with formic acid (4.8 mL). The reaction mixture was exposed to microwave irradiation at 595 W for 7 minutes. After cooling to room temperature, 10% NaOH solution was gradually added with stirring to neutralize the acidic medium and promote product precipitation. The solid obtained was filtered, washed with chilled water, and recrystallized in the presence of decolorizing charcoal. The final product was collected and dried for further use.

Figure no. 06: Synthesis of N-formyl-4-(1H-benzimidazole-2-yl) Benzenamide from the intermediate using formic acid.

Synthesis of N-(4-(1H-benzimidazole-2-yl) Benzyl) Acetamide: In a similar procedure, 4-(2, 3-dihydro-1H-1, 3-benzodiazole-2-yl) aniline (8.1 g) was treated with acetic acid (4.8 mL) in a round-bottom flask. The reaction was irradiated in a microwave at 595 W for 7 minutes. Upon completion, the mixture was allowed to cool, and 10% sodium hydroxide solution was added dropwise until the precipitation of the product was observed. The solid was collected by vacuum filtration, washed with cold water, and recrystallized with activated charcoal for purity enhancement. The final product was dried and stored.

Figure no. 07: Synthesis of N-(4-(1H-benzimidazole-2-yl) Benzyl) Acetamide using acetic acid.

Reaction Scheme:

Figure no. 08: Reaction scheme illustrating the synthesis of MSB-7 and MSB-8 Benzimidazole derivatives via microwave-assisted reactions.

RESULTS:

Antioxidant Activity (DPPH Assay): The antioxidant potential of synthesized Benzimidazole derivatives was assessed using the DPPH radical scavenging assay. The results showed that MSB 3 exhibited the highest activity (75.74%), all showing strong activity comparable to the standard (83.22%). Compounds MSB 2 (61.53%) also demonstrated notable activity. while MSB 1 displayed moderate activity (55.92%). The variation in activity is likely influenced by the electronic and steric effects of substituents on the Benzimidazole ring. These findings highlight  MSB 1, 2, and 3 as encouraging antioxidant candidates for further development the result shown in figure no 09 and table no 01.

Figure no. 09: % DPPH radical scavenging activity of resultant compounds.

Table no. 01: % DPPH radical scavenging activity of synthesized compounds (Benzimidazole derivatives). ^11-12