Effects of Botanical Variation, Plant Part, and Extraction Technique on Mitragynine and 7-Hydroxymitragynine in Kratom (Mitragyna speciosa) Extracts Quantified by a Validated HPLC–DAD Method

Mitragyna speciosa (kratom) is a traditionally consumed botanical rich in the bioactive alkaloids mitragynine (MG) and 7-hydroxymitragynine (7OH-MG). This study evaluated the influence of botanical variation, plant part, geographical origin, and extraction technique on alkaloid composition and extraction yield. A validated HPLC–DAD method was applied to quantify MG and 7OH-MG in leaf and shoot extracts. Ethanol-based ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were used for samples from northern and southern Thailand. Significant compositional differences were observed. Green-veined leaves contained higher MG levels than red-veined leaves. Northern samples showed higher extraction yields and MG contents, whereas southern samples exhibited relatively higher 7OH-MG levels. Differences between UAE and MAE were minimal. Notably, 7OH-MG was detected only in leaves, while shoots contained higher MG concentrations despite lower yields. These findings highlight substantial phytochemical variability relevant to quality standardization of kratom-derived products.