A revision of the genus Mitragyna (Rubiaceae) in Thailand is reported. Four species, i.e. M. diversifolia, M. hirsuta, M. rotundifolia, and M. speciosa are described in this taxonomic treatment. A summary of taxonomic history, detailed morphological descriptions, distributions, ecology, phenology, vernacular names, uses, IUCN conservation status, specimens examined, photographs and a key to the species are proposed. Two names are lectotypified: M. rotundifolia and M. speciosa.
We analyzed the content of mitragynine (MG) found in kratom leaves (Mitragyna speciosa) and the influence of different environmental conditions (air and soil variables) on the yield in various regions of Thailand. The content of MG in kratom leaves ranged from 7.5 – 26.6 mg g-1 of dry leaf weight. Canonical correspondence analysis showed that the most significant environmental variables affecting the MG content among the various regions were light intensity, relative humidity, soil volumetric water content (VW), soil pH, and calcium. This study is a first step towards providing information about environmental conditions suitable to maximize the quality and quantity of bioactive alkaloids in kratom. Future studies should focus on leaf collection and the post-harvest processes in order to assure the desired alkaloidal content in finished products, when produced under suitable environmental conditions identified in this study.
In Thailand two species of Dumasia occur, D. villosa subsp. villosa and D. yunnanensis. They grow in montane and dry evergreen forests, in open or disturbed areas and limestone ridges 550-2,500 meters above sea level, in northern, northeastern, and central Thailand. We present a key to the two Thai Dumasia based on their vegetative, flowering and fruiting characters, and provide nomenclature, descriptions, photographs, illustrations, and information about their distribution and ecology.
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