Mesembrine-d3 is primarily used in research and analytical applications as a deuterated internal standard. It aids in the accurate quantification of mesembrine and related alkaloids in biological samples using techniques like mass spectrometry. This compound is particularly valuable in pharmacokinetic studies, where it helps track the absorption, distribution, metabolism, and excretion of mesembrine in organisms. Additionally, it supports the development of analytical methods for quality control in the production of plant extracts, ensuring consistency and safety in products derived from Sceletium tortuosum. Its use enhances precision in scientific investigations, contributing to advancements in pharmacology and natural product research.