Data Sheet 1_Alkaloid biosynthesis in medicinal crop kratom (Mitragyna speciosa) varies with postharvest, genetic, and seasonal factors.docx

IntroductionKratom (Mitragyna speciosa), a medicinally valuable ethnobotanical tree native to Southeast Asia, has traditionally been used to combat fatigue and enhance productivity. Recently, it has gained attention in North America and Europe for its potential therapeutic applications, particularly in pain management and opioid withdrawal, positioning it as a candidate for drug development. Postharvest processing is a critical stage that influences chemical transformations of bioactive compounds, yet its impact on kratom remains poorly understood.
MethodsThis study investigated the effects of withering duration, drying temperature, cultivar, and season on kratom alkaloid composition and concentration. In Study I, leaves of cultivar Hawaii underwent four withering durations (0, 12, 24, 72 h) followed by drying at five temperatures (−40, 25, 40, 60, 80 °C). In Study II, leaves of cultivar MR-Malaysian were tested under two withering durations (0, 12 h) and two drying temperatures (25, 60 °C). Both studies were conducted across two seasons.
ResultsWithering generally increased mitragynine concentrations by 14-65% (w/w) in 'Hawaii' and 3-8% in 'MR-Malaysian' in leaf alkaloid extracts. A 12-h withering followed by drying below 40 °C enhanced speciogynine and paynantheine in 'Hawaii' by 37-48% and 35-67%, respectively. Low drying temperatures preserved mitragynine, speciogynine, and paynantheine across cultivars. The average 7-hydroxymitragynine content in leaf alkaloid extracts ranged from 0.02-0.04% and was detected only in specific seasons, varying by cultivar, suggesting genotype-environment interactions.
DiscussionThis study demonstrates for the first time that kratom alkaloid composition and concentration are substantially influenced by genotype, season, and postharvest handling. These findings underscore the importance of optimizing postharvest processing strategies to enhance beneficial alkaloid profiles in kratom.

### 引言
帽柱木（Mitragyna speciosa）是一种原产于东南亚的具有药用价值的民族植物学树木，传统上被用于对抗疲劳、提升工作效率。近年来，其在北美与欧洲受到广泛关注，因其潜在的治疗应用价值，尤其在疼痛管理与阿片类药物戒断方面，成为药物开发的候选对象。采后处理是影响生物活性成分化学转化的关键环节，但目前关于采后处理对帽柱木的影响仍知之甚少。

### 方法
本研究考察了萎凋时长、干燥温度、品种及季节对帽柱木生物碱组成与浓度的影响。试验一：选取夏威夷品种的叶片，设置4种萎凋时长（0、12、24、72小时），随后在5种温度（-40、25、40、60、80℃）下进行干燥处理。试验二：选取MR-马来西亚品种的叶片，在2种萎凋时长（0、12小时）与2种干燥温度（25、60℃）条件下开展测试。两项试验均在两个季节中进行。

### 结果
萎凋处理通常可使‘夏威夷’品种叶片生物碱提取物中的米氏帽柱木碱（mitragynine）含量提升14%~65%（质量分数），使‘MR-马来西亚’品种提升3%~8%。经12小时萎凋后于40℃以下干燥，可使‘夏威夷’品种中的细叶帽柱木碱（speciogynine）与潘他明碱（paynantheine）含量分别提升37%~48%与35%~67%。较低的干燥温度可保留两个品种中的米氏帽柱木碱、细叶帽柱木碱与潘他明碱。叶片生物碱提取物中7-羟基米氏帽柱木碱（7-hydroxymitragynine）的平均含量为0.02%~0.04%，仅在特定季节可检出，且因品种而异，提示存在基因型-环境互作效应。

### 讨论
本研究首次证实，帽柱木的生物碱组成与浓度显著受基因型、季节及采后处理方式的影响。上述研究结果凸显了优化采后加工策略以提升帽柱木有益生物碱组分的重要性。