2-Amino- N-Phenethylbenzamides for Irritable Bowel Syndrome Treatment

Abstract

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder characterized by abdominal pain or discomfort. Mebeverine is an antispasmodic that has been widely used in clinical practice to relieve the symptoms of IBS. However, its systemic use usually leads to side effects. Therefore, the current paper aimed to synthesize more effective medicines for IBS treatment. We used ring opening of isatoic anhydride for the synthesis in reaction with 2-phenylethylamine. In silico simulation predicted spasmolytic activity for 2-amino-N-phenethylbenzamides. The newly synthesized compounds demonstrated a relaxation effect similar to mebeverine but did not affect the serotonin or Ca²⁺-dependent signaling pathway of contractile activity (CA) in contrast. Having in mind the anti-inflammatory potential of antispasmodics, the synthesized molecules were tested in vitro and ex vivo for their anti-inflammatory effects. Four of the newly synthesized compounds demonstrated very good activity by preventing albumin denaturation compared to anti-inflammatory drugs/agents well-established in medicinal practice. The newly synthesized compounds also inhibited the expression of interleukin-1β and stimulated the expression of neuronal nitric oxide synthase (nNOS), and, consequently, nitric oxide (NO) synthesis by neurons of the myenteric plexus. This characterizes the newly synthesized compounds as biologically active relaxants, offering a cleaner and more precise application in pharmacological practice, thereby enhancing their potential therapeutic value.

Keywords: anti-inflammatory activity; denaturation of albumin; mebeverine; spasmolytic activity; synthesis.

Scheme 1

Synthesis of the 2-amino-N-phenethylbenzamides 3 and 4a–d.

Figure 1

Changes in SM tissue parameters: (A) tone in mN; and (B) amplitude in %, induced by compounds 3 and 4a–d (5 × 10⁻⁵ M) (n = 12). Statistically significant differences: * p < 0.05 comparison is between mebeverine and 3, 4a–d.

Figure 1

Changes in SM tissue parameters: (A) tone in mN; and (B) amplitude in %, induced by compounds 3 and 4a–d (5 × 10⁻⁵ M) (n = 12). Statistically significant differences: * p < 0.05 comparison is between mebeverine and 3, 4a–d.

Figure 2

Representative tracings demonstrating the contractile responses of SMPs from the gastric corpus of rats following the application of mebeverine compared to the application of substances 4a and 4c, subsequently followed by an ACh reaction in their background.

Figure 3

IC₅₀ inhibition of albumin denaturation (in mg/mL) of newly synthesized hybrids (yellow). Diclofenac (red) and acetylsalicylic acid (green) were used as standards. The lower the value, the higher the anti-inflammatory activity.

Figure 4

Micrographs of SM stomach corpus preparations with newly synthesized compounds (the incubation period was 3 h): (A) control, IL-1β expression (black arrow), at ×400; (B,C) SMPs incubated with substance 3, 4a expression of IL-1β (black arrow), at ×400; (D) SMPs incubated with substance 4c, lack of IL-1β expression in myenteric plexus, weak in mucosal glands, at ×400; (E) SMPs incubated with substance 4b, lack of IL-1β expression, at ×400; (F) control, nNOS expression (orange arrow) at ×400; (G,H) SMPs incubated with substances 3 and 4a, lack of nNOS expression, at ×400; and (I,J) SMPs incubated with substances 4b and 4c, increased expression of nNOS in the myenteric plexus (orange arrow), at ×400.

Figure 5

Expression of IL-1β in the SMPs incubated with the newly synthesized compounds 3 and 4. The asterisk indicates significant differences between groups—*** p < 0.001.

Figure 6

Expression of nNOS in the SMPs incubated with the newly synthesized compounds 3 and 4. The asterisk indicates significant differences between groups—*** p < 0.001.