Cuiying Ma

Ethnobotanical approach versus random approach in the search for new bioactive compounds: Support of a hypothesis

Context: Whether natural product drug discovery programs should rely on wild plants collected “randomly” from the natural environment, or whether they should also include plants collected on the basis of use in traditional medicine remains an open question. Objective: This study analyzes whether plants with ethnomedical uses from Vietnam and Laos have a higher hit rate in bioassay testing than plants collected from a national park in Vietnam with the goal of maximizing taxonomic diversity (“random” collection). Materials and Methods: All plants were extracted and subjected to bioassay in the same laboratories. Results of assays of plant collections and plant parts (samples) were scored as active or inactive based on whether any extracts had a positive result in a bioassay. Contingency tables were analyzed using χ2 statistics. Results: Random collections had a higher hit rate than ethnomedical collections, but for samples, ethnomedical plants were more likely to be active. Ethnomedical collections and samples had higher hit rates for tuberculosis, while samples, but not collections, had a higher hit rate for malaria. Little evidence was found to support an advantage for ethnomedical plants in HIV, chemoprevention and cancer bioassays. Plants whose ethnomedical uses directly correlated to a bioassay did not have a significantly higher hit rate than random plants. Discussion: Plants with ethnomedical uses generally had a higher rate of activity in some drug discovery bioassays, but the assays did not directly confirm specific uses. Conclusions: Ethnomedical uses may contribute to a higher rate of activity in drug discovery screening.

Study of Antimalarial Activity of Chemical Constituents from Diospyros quaesita

Bioassay‐directed fractionation led to the isolation of seven compounds from a sample of the dried leaves, twigs, and branches of Diospyros quaesita Thw. (Ebenaceae). One of the isolates, betulinic acid 3‐caffeate (1), showed in vitro antimalarial activity against Plasmodium falciparum clones D6 (chloroquine‐sensitive) and W2 (chloroquine‐resistant) with IC50 values of 1.40 and 0.98 μM, respectively. Evaluation of compound 1 in the human oral epidermoid (KB) cancer cell line revealed cytotoxicity at ED50 of 4.0 μM. In an attempt to reduce the cytotoxicity of 1, the acetylated derivative 1a and betulinic acid (1b) were prepared. Of the seven isolates, diospyrosin (2) was determined to be a new neolignan. In addition to 1, other known compounds isolated in this study were pinoresinol, lariciresinol, N‐benzoyl‐L‐phenylalaninol, scopoletin, and poriferast‐5‐en‐3β,7α‐diol. The structure of 2 was elucidated based on spectroscopic data analysis including 1D‐ and 2D‐NMR, and HR‐ESI‐MS.

Antimalarial Activity of Aspilia pruliseta, a Medicinal Plant from Uganda

Aspilia pruliseta Schweinf. (Asteraceae) is a medicinal plant indigenous to Uganda and the neighboring countries of East Africa. It has been used extensively by the rural population for the treatment of fevers and malaria. During the antimalarial evaluation of this plant, four nontoxic diterpenes were isolated that possessed moderate activity against chloroquine-sensitive (D6) and chloroquine-resistant (W2) clones of Plasmodium falciparum, with IC(50) values ranging from 14 to 23 µM. These moderately active compounds included the previously undescribed diterpene, ENT-15 β-senecioyloxy-16,17-epoxy-kauran-18-oic acid that demonstrated an IC(50) value of 23.4 µM against clone D6, but was devoid of activity against clone W2. Four additional diterpenes were obtained from the aerial parts of A. pruliseta, but these known compounds were essentially inactive. The moderate activities of select diterpenes of A. pruliseta could account collectively for the historical and enduring use of this plant in traditional African medicine.