Crinum Latifolium Leave Extracts Suppress Immune Activation Cascades in Peripheral Blood Mononuclear Cells and Proliferation of Prostate Tumor Cells

Plants of the genus Crinum (Amaryllidaceae) are widely used in folk medicine in different tropical and subtropical regions around the world. The Indian species Crinum latifolium (L.) was traditionally used to treat rheumatism, fistula, tumors, earaches, rubefacient, tubercle and whitlow. In Vietnamese and Chinese traditional medicine Crinum latifolium preparations are used until nowadays because of their antiviral and antitumor properties. In this study, we demonstrate potent in vitro antioxidant activity of an aqueous Crinum latifolium extract by an oxygen radical absorbance capacity (ORAC) value of 1610 ± 150 μmol Trolox equivalents/g. Furthermore, significant anti-inflammatory effects of this extract were shown by its potential to suppress indoleamine 2,3-dioxygenase (IDO) mediated tryptophan degradation in unstimulated- and mitogen-stimulated PBMC at IC₅₀ doses of 241 ± 57 μg/ml and 92 ± 20 μg/ml, respectively. Concentrations of the immune activation marker neopterin were slightly diminished in unstimulated PBMC, whereas a dose-dependent inhibition of neopterin formation was observed in mitogen-stimulated PBMC (IC₅₀ = 453 ± 86 μg/ml). Additionally, we measured also dose-dependent inhibitory effects of this aqueous Crinum latifolium extract on cell proliferation of highly metastatic human prostate carcinoma PC3 cells (IC₅₀ = 4.5 ± 0.8 mg/ml), androgensensitive prostate adenocarcinoma LNCaP cells (IC₅₀ =2.3 ± 0.1 mg/ml), and benign prostate hyperplasia BPH-1 cells (IC₅₀ = 2.1 ± 0.04 mg/ml). We conclude that both effects, inhibition of tumor cell growth and recovery of immune functions, are important for the antitumor properties of Crinum latifolium.