ABSTRACT
We previously observed that rhinacanthins-C, -N and -Q, three main naphthoquinone esters isolated from the roots of Thai medicinal plant; Rhinacanthus nasutus KURZ. (Acanthaceae) induced apoptosis of human cervical carcinoma HeLaS3 cells. Since these rhinacanthins showed limited solubility in aqueous medium, we attempted to entrap them into liposomal membrane: Liposomalization enabled injection of the drugs and the drugs were expected to transfer to lipoproteins in the bloodstream. Liposomal formulations of rhinacanthins-C, -N and -Q showed strong antiproliferative activity against HeLaS3 cells with the IC50 values of 32, 17, 70 microM; 19, 17, 52 microM and 2.7, 2.0 and 5.0 microM for the exposure time of 24, 48, and 72 h, respectively. These liposomes suppressed the tumor growth in Meth-A sarcoma-bearing BALB/c mice at the dose of 5.0 mg/kg/d for 10 d. Among rhinacanthins, liposomal rhinacanthin-N significantly suppressed solid tumor growth. Based on these results, our findings demonstrated that rhinacanthin-N suppressed tumor growth in vivo, and suggested that liposomes are useful for preparing injectable formulation of hydrophobic drugs.
Subject(s)
Acanthaceae/chemistry , Antineoplastic Agents, Phytogenic/pharmacology , Naphthoquinones/pharmacology , Plants, Medicinal/chemistry , Animals , Antineoplastic Agents, Phytogenic/chemistry , Antineoplastic Agents, Phytogenic/isolation & purification , Ascites/pathology , Ascites/prevention & control , Cell Line, Tumor , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Esters , HeLa Cells , Humans , Lignans/chemistry , Lignans/isolation & purification , Lignans/pharmacology , Liposomes , Male , Mice , Mice, Inbred BALB C , Molecular Structure , Naphthoquinones/chemistry , Naphthoquinones/isolation & purification , Neoplasm Transplantation/methods , Phytotherapy/methods , Plant Extracts/chemistry , Plant Extracts/pharmacology , Plant Roots/chemistry , Sarcoma, Experimental/pathology , Sarcoma, Experimental/prevention & control , Survival Analysis , ThailandABSTRACT
Rhinacanthus nasutus KURZ. (Acanthaceae) has been used as Thai traditional medicine for the treatment of various cancers. Recently, we reported that rhinacanthins, active components of the plant, had antiproliferative activity against human cancer line cells. In the present study, we investigated the growth inhibitory mechanism of rhinacanthins-C, -N and -Q, three main naphthoquinone esters isolated from the roots of R. nasutus KURZ. in human cervical carcinoma (HeLaS3) cells by means of TUNEL staining, DNA fragmentation assay, flow cytometry, and cleavage assay of Asp-Glu-Val-Asp-peptide-nitroanilide, a caspase-3 substrate. After the HeLaS3 cells was exposed with different concentrations of the drugs, rhinacanthins-C, -N and -Q exhibited antiproliferative effects on HeLaS3 cells with the IC50 values of 80, 65, 73 microM; 55, 45, 55 microM; and 1.5, 1.5 and 5.0 microM for 24, 48 and 72 h time points, respectively. Morphological changes showing nuclear fragmentation of rhinacanthins-treated cells were clearly observed after 48 h exposure. Consistent with this observation, the appearance of a ladder formation was also evident with an agarose gel electrophoresis of the extracted DNA. Flow cytometric analysis revealed that rhinacanthin-N caused G2/M arrest of HeLaS3 cells after 24 h incubation, and increased the proportion of sub-G1 hypodiploid cells, apoptotic cells, in the population of HeLaS3 cells after 48 and 72 h incubation. Moreover, the drug treatment markedly elevated the activity of caspase-3. Based on these results, our findings demonstrated for the first time that the inhibitory effects of three main naphthoquinone esters isolated from the roots of R. nasutus KURZ. on the growth of HeLaS3 cells appear to arise from the induction of apoptosis, that might be associated with the activation of caspase-3 pathway.
