Cytotoxic Evaluation of a Novel Herbal Topical Anesthetic Gel on Human Mesenchymal Stem Cells: An In Vitro Study

Abstract

Background: Herbal products are gaining attention in dentistry as safer alternatives to synthetic agents. Spilanthesacmella, a medicinal plant with known anesthetic properties, contains spilanthol, which produces a characteristic numbing effect. However, its cytotoxic profile on human cells must be established before clinical application.

Aim: To evaluate the cytotoxicity of a novel herbal topical anesthetic gel containing S. acmella on human mesenchymal stem cells (hMSCs).

Materials and Methods: An herbal gel was prepared using Soxhlet extraction of S. acmella whole plant powder, incorporated into a polyethylene glycol base, and flavored for palatability. hMSCs were cultured and exposed to varying concentrations (100–1000 µg/mL) of the gel for 24 hours. Cytotoxicity was assessed using the MTT assay, and absorbance was measured at 570 nm to determine cell viability.

Results: The gel demonstrated a concentration-dependent cytotoxic effect. At 100 µg/mL, cell viability was 90.34%, while at 200 µg/mL it declined to 78.98%. Further increases in concentration resulted in progressively lower viability, with only 39.02% survival at 1000 µg/mL. The half maximal inhibitory concentration (IC₅₀) was calculated as 803.52 µg/mL. Based on these findings, the maximum recommended safe concentration was 0.8 mg.

Conclusion: The S. acmella herbal anesthetic gel exhibited high biocompatibility at lower concentrations and dose-dependent cytotoxicity at higher concentrations. These results indicate its potential as a safe, natural topical anesthetic in pediatric dentistry, warranting further in vivo and clinical validation.