Abstract
Leaves harvested from the Southeast Asian tree Mitragyna speciosa (kratom) have a history of use as a traditional ethnobotanical source of medicine to combat fatigue, improve work productivity, and to reduce opioid-related withdrawal symptoms. Kratom leaves contain an array of alkaloids thought to be responsible for the bioactivity reported by users. Interest in the consumptive effects of kratom has led to its recent popularity and use in North America, Western Europe, and Australia. Although the chemistry and pharmacology of select kratom alkaloids are understood, studies have not examined the influence of production environment on growth and alkaloidal content. To directly address this need, 68 kratom trees were vegetatively propagated from a single mother stock to reduce genetic variability and subjected to four varying fertilizer application rates. Leaves were analyzed for chlorophyll concentration, biomass, and alkaloidal content to understand the physiological response of the plant. While increasing rates of fertilizer promoted greater plant growth, relationships with alkaloidal content within leaves were highly variable. Fertility rate had little influence on the concentration of mitragynine, paynantheine, speciociliatine, mitraphylline, and corynoxine per leaf dry mass. 7-Hydroxymitragynine was below the lower limit of quantification in all the analyzed leaf samples. Low to medium rates of fertilizer, however, maximized concentrations of speciogynine, corynantheidine, and isocorynantheidine per leaf dry mass, suggesting a promotion of nitrogen allocation for secondary metabolism occurred for these select alkaloids. Strong correlations (r2 = 0.86) between extracted leaf chlorophyll and rapid, non-destructive chlorophyll evaluation (SPAD) response allowed for development of a reliable linear model that can be used to diagnose nutrient deficiencies and allow for timely adjustment of fertilization programs to more accurately manage kratom cultivation efforts. Results from this study provide a greater understanding of the concentration and synthesis of nine bioactive alkaloids in fresh kratom leaves and provide foundational information for kratom cultivation and production.
Highlights
Mitragyna speciosa, known as kratom in Thailand or ketum in Malaysia, is a facultatively deciduous small to medium size (4–16 m) tropical tree native to southern Thailandnorth peninsular Malaysia, Sumatra, Borneo, Philippines, and New Guinea, but is reported in Vietnam and Myanmar (Suwanlert, 1975; Puff, 2007)
Fertilizer application rate influenced speciociliatine concentrations on only one sampling date (November 13, 2018; Table 1) where inverse relationships were observed between speciociliatine and fertilizer rate
As a new emerging crop, relevant information on kratom cultivation is limited despite its long cultivation history in southeast Asia
Summary
Known as kratom in Thailand or ketum in Malaysia, is a facultatively deciduous small to medium size (4–16 m) tropical tree native to southern Thailandnorth peninsular Malaysia, Sumatra, Borneo, Philippines, and New Guinea, but is reported in Vietnam and Myanmar (Suwanlert, 1975; Puff, 2007). Interest in the application and use of kratom emerged within North America, Western Europe, and Australia in the late 20th century (NIDA, 2019). Within these newly emerged markets, kratom is sold as a concentrated liquid extract or as dried, ground leaf powder that is oftentimes encapsulated for consumptive ease. Differences in preparation and use have likely contributed to reports of toxicity and mortality among new users in the United States and Europe. Despite growing health concerns surrounding recreational consumption of kratom, research examining medical application of kratom as a potential pharmaceutical alternative to opioid-based medication is ongoing and supported given its reported traditional use to combat opiate withdrawal (Boyer et al, 2008)
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