Crinum Latifolium Leave Extracts Suppress Immune Activation Cascades in Peripheral Blood … 329 Experimental Preparation of the aqueous Crinum latifolium extract The dry extract of Crinum latifolium leaves from CriLa® capsules (250 mg), obtained by the Thien Duoc Company Ltd. (Ho Chi Minh City, Vietnam), was standardized with reference to the amount of crinamidine content (70 µg/capsule) using reverse phase high performance liquid chromatography (HPLC; Figure 3). Content of total alkaloids was also measured by HPLC and calculated with reference to lycorin, which revealed 1.25 ± 0,13 mg total alkaloids/capsule. Leaves from Crinum latifolium L. were collected in April and July at the District of Go Vap, Ho Chi Min City, Vietnam. A voucher specimen is kept at the Nguyen Thi Ngoc Tkam Herbarium. The identity of the plant was confirmed by Prof. Dr. Sc. Tkan Cong Khanh, Department of Botany, Hanoi College of Pharmacy, Center for Research and Development of Ethnomedicinal Plants (CREDEP). In this study, 250 mg of the dry powder of a CriLa® capsule was extracted for 1 hour using 50 ml of cell culture media (RPMI) at room temperature. Thereafter, the extract was sterile filtered and stored at room temperature until analysis. Fig. 3. HPLC chromatogram of crinamidine standard (RT 33 min; A), and the dry extract of Crinum latifolium leaves (B). Cell culture PBMC were isolated from whole blood obtained from healthy donors, of whom informed consent was obtained that their donated blood unit was used for scientific purposes if not otherwise used. Separation of blood cells was performed using density centrifugation (Lymphoprep, Nycomed Pharma AS, Oslo, Norway). After isolation, PBMC were washed three times in phosphate buffered saline containing 0.2% EDTA [0.5 mmol/L]. Cells were Sci Pharm. 2011; 79: 323–335