Essential oil from leaves of Conobea scoparioides (Cham. & Schltdl.) Benth. (Plantaginaceae) causes cell death in HepG2 cells and inhibits tumor development in a xenograft model.

Conobea scoparioides (Cham. & Schltdl.) Benth. (syn. Sphaerotheca scoparioides Cham. & Schldtl.) (Plantaginaceae), popularly known as "pataqueira", "vassourinha-do-brejo" and/or "hierba-de-sapo", is a popular medicinal plant used to treat leishmaniasis, pain and beriberi. In addition, inhibition of cell adhesion, antioxidant, cytotoxic and leishmanicidal activities of compounds or fractions of C. scoparioides have been reported. In the present work, chemical constituents and in vitro and in vivo anti-liver cancer potential of essential oil (EO) from leaves of C. scoparioides were investigated using human hepatocellular carcinoma HepG2 cells as a cell model. EO was obtained by hydrodistillation using a Clevenger-type apparatus and characterized by GC-MS and GC-FID. The in vitro cytotoxic effect was evaluated on three human cancer cell lines (MCF-7, HepG2 and HCT116) and one human non-cancerous cell line (MRC-5) using the Alamar blue assay. Phosphatidylserine externalization and cell cycle distribution were quantified in HepG2 cells by flow cytometry after 48 h incubation. The effectiveness of EO in anti-liver cancer model was studied with HepG2 cells grafted on C.B. 17 SCID mice. The main constituents of EO were thymol methyl ether (62 %), thymol (16 %) and α-phellandrene (14 %). EO displayed an in vitro cytotoxic effect against all human cancer cell lines and caused externalization of phosphatidylserine and DNA fragmentation in HepG2 cells, suggesting induction of apoptotic-like cell death. In vivo tumor mass inhibition of 36.7 and 55.8 % was observed for treatment with EO at doses of 40 and 80 mg/kg, respectively. These results indicate in vitro and in vivo anti-liver cancer potential of EO from leaves of C. scoparioides.

Antitumor Effect of the Essential Oil from the Leaves of Croton matourensis Aubl. (Euphorbiaceae).

Croton matourensis Aubl. (synonym Croton lanjouwensis Jabl.), popularly known as "orelha de burro", "maravuvuia", and/or "sangrad'água", is a medicinal plant used in Brazilian folk medicine as a depurative and in the treatment of infections, fractures, and colds. In this work, we investigated the chemical composition and in vitro cytotoxic and in vivo antitumor effects of the essential oil (EO) from the leaves of C. matourensis collected from the Amazon rainforest. The EO was obtained by hydrodistillation using a Clevenger-type apparatus and characterized qualitatively and quantitatively by gas chromatography coupled to mass spectrometry (GC⁻MS) and gas chromatography with flame ionization detection (GC⁻FID), respectively. In vitro cytotoxicity of the EO was assessed in cancer cell lines (MCF-7, HCT116, HepG2, and HL-60) and the non-cancer cell line (MRC-5) using the Alamar blue assay. Furthermore, annexin V-FITC/PI staining and the cell cycle distribution were evaluated with EO-treated HepG2 cells by flow cytometry. In vivo efficacy of the EO (40 and 80 mg/kg/day) was demonstrated in C.B-17 severe combined immunodeficient (SCID) mice with HepG2 cell xenografts. The EO included ß-caryophyllene, thunbergol, cembrene, p-cymene, and ß-elemene as major constituents. The EO exhibited promising cytotoxicity and was able to cause phosphatidylserine externalization and DNA fragmentation without loss of the cell membrane integrity in HepG2 cells. In vivo tumor mass inhibition rates of the EO were 34.6% to 55.9%. Altogether, these data indicate the anticancer potential effect of C. matourensis.