An internal standard suitable for quantitation of mitragynine in biological samples using mass spectrometry-based methods. Mitragynine, commonly known as Kratom, is the most abundant alkaloid in the plant Mitragynine speciosa. Sold over the internet as herbal plant extracts, Kratom is noted for its psychoactive, stimulant, and sedative effects depending on the dosage level. According to DEA’s Drugs and Chemicals of Concern page, mitragynine use can lead to addiction with adverse effects ranging from anorexia and weight loss to hallucinations and delusion.