One-Step Isolation of Monoterpene Indole Alkaloids from Psychotria leiocarpa Leaves and Their Antiviral Activity on Dengue Virus Type-2

The leaf MeOH extract of Psychotria leiocarpa (Rubiaceae) showed in vitro non-cytotoxic and anti-dengue virus serotype 2 (DENV2) activity in human hepatocarcinoma cell lineage (HepG2). A one-step and cost-effective reversed-phase solid-phase extraction method based on high-performance liquid chromatography (HPLC) parameters allowed the isolation, directly from this bioactive extract, of the monoterpene indole alkaloids: N-glucopyranosyl vincosamide (1), vincosamide (2) and strictosidinic acid (3). The chemical structures were characterized based on 1D and 2D nuclear magnetic resonance (NMR), UV and high-resolution mass spectra (HRMS). The methodology has also allowed yielding a polyphenolic-rich fraction that was analyzed by high-performance liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS/MS) revealing two flavonol triglycosides (4, 5) and three caffeoylquinic acid isomers (6-8). Compound 3 is reported for the first time in P. leiocarpa and all the phenolic compounds (4-8) are described for the first time in the genus Psychotria. Compounds 1-3 showed to be non-cytotoxic and anti-dengue active towards DENV2, highlighting vincosamide (2).

光果九节（Psychotria leiocarpa）隶属于茜草科（Rubiaceae），其叶片甲醇提取物在人类肝癌细胞系（HepG2）中展现出体外无细胞毒性及抗登革病毒2型（DENV2）的活性。基于高效液相色谱（HPLC）参数建立的一步法、经济高效的反相固相萃取方法，可直接从该生物活性提取物中分离得到单萜吲哚生物碱：N-葡萄糖基文卡酰胺（N-glucopyranosyl vincosamide）(1)、文卡酰胺（vincosamide）(2)与斯特里科西迪尼酸（strictosidinic acid）(3)。上述化合物的化学结构通过一维和二维核磁共振波谱（NMR）、紫外光谱（UV）及高分辨质谱（HRMS）得以表征。该方法同时获得了富含多酚的组分，经高效液相色谱-二极管阵列检测-电喷雾电离串联质谱（HPLC-DAD-ESI-MS/MS）分析，鉴定出2种黄酮醇三糖苷（4、5）与3种咖啡酰奎宁酸异构体（6~8）。化合物3在光果九节中为首次报道，所有酚类化合物（4~8）均为九节属（Psychotria）首次报道。化合物1~3均表现出无细胞毒性且抗DENV2的活性，其中文卡酰胺(2)的活性尤为突出。