Medical Ethnobotany And The Search For New Anticancer Agents From Plants Of Laos And Vietnam

Field botanical research and phytochemistry research were pursued to evaluate the anticancer drug discovery potential of medicinal plants from mainland Southeast Asia (Laos and Vietnam). Collection and documentation of 201 samples from 96 medicinal plant taxa proceeded from two different Lao tropical forest preserves (Xiengkhouang Medicinal Biodiversity Preserve and Bolikhamxay Medicinal Plant Preserve) managed by local communities. Subsequent cytotoxicity testing of the extracts of these samples in the HT-29 human colon adenocarcinoma cell line revealed that six of the samples had bioactivity significant enough to merit re-collection and further study. None of these plants were used in Laos for cancer treatment, and only three of six collections were from the plant part employed locally in ethnomedicine, demonstrating that liberal collection of plant parts from medicinal plants is an effective strategy in maximizing the hit rate for unanticipated bioactivity. Two plant parts from a Vietnamese collection of Streptocaulon juventas (Lour.) Merr. (AA06944/LF+TW and AA06945/ST; Apocynaceae) were extracted, partitioned, and fractionated towards the isolation of cytotoxic components. Separation procedures yielded a known cardiac glycoside, corchorusoside C, with submicromolar cytotoxicity, not previously reported in HT-29 cells and other human tumor cell lines tested, from the leaf and twig material (AA06944/LF+TW). This work allowed for further cytotoxicity and mechanistic studies of corchorusoside C and additional isolates that originated from the stem material (AA06945/ST). These research activities are discussed and analyzed both in terms of their own merit and potential and from the broader perspective of negotiating and abiding by international collection agreements for plant-based bioprospecting in Southeast Asia and worldwide, in anticancer drug discovery paradigms and beyond.