Medicinal plants are one of the most important sources of drugs used in the pharmaceutical industry. Among traditional medicinal plants, Lippia gracilis Schauer (Verbenaceae) had been used for several medicinal purposes in Brazilian northeastern. In this study, leaf essential oil (EO) of L. gracilis was prepared using hydrodistillation. Followed by GC-MS analysis, its composition was characterized by the presence of thymol (55.50%), as major constituent. The effects of EO on cell proliferation and apoptosis induction were investigated in HepG2 cells. Furthermore, mice bearing Sarcoma 180 tumor cells were used to confirm its in vivo effectiveness. EO and its constituents (thymol, p-cymene, γ-terpinene and myrcene) displayed cytotoxicity to different tumor cell lines. EO treatment caused G1 arrest in HepG2 cells accompanied by the induction of DNA fragmentation without affecting cell membrane integrity. Cell morphology consistent with apoptosis and a remarkable activation of caspase-3 were also observed, suggesting induction of caspase-dependent apoptotic cell death. In vivo antitumor study showed tumor growth inhibition rates of 38.5-41.9%. In conclusion, the tested essential oil of L. gracilis leaves, which has thymol as its major constituent, possesses significant in vitro and in vivo antitumor activity. These data suggest that leaf essential oil of L. gracilis is a potential medicinal resource.

Guatteria friesiana (W. A. Rodrigues) Erkens & Maas (synonym Guatteriopsis friesiana W. A. Rodrigues), popularly known as "envireira", is a medicinal plant found in the Brazilian and Colombian Amazon basin that is used in traditional medicine for various purposes. Recent studies on this species have demonstrated antimicrobial activity. In this study, the antitumor activity of the essential oil from the leaves of G. friesiana (EOGF) and its main components ( α-, β-, and γ-eudesmol) were determined using experimental models. In the in vitro study, EOGF and its components α-, β-, and γ-eudesmol displayed cytotoxicity against tumor cell lines, showing IC₅₀ values in the range of 1.7 to 9.4 µg/mL in the HCT-8 and HL-60 cell lines for EOGF, 5.7 to 19.4 µg/mL in the HL-60 and MDA-MB-435 cell lines for α-eudesmol, 24.1 to > 25 µg/mL in the SF-295 and MDA-MB-435 cell lines for β-eudesmol, and 7.1 to 20.6 µg/mL in the SF-295 and MDA-MB-435 cell lines for γ-eudesmol, respectively. In the in vivo study, the antitumor effect of EOGF was evaluated in mice inoculated with sarcoma 180 tumor cells. Tumor growth inhibition rates were 43.4-54.2 % and 6.6-42.8 % for the EOGF treatment by intraperitoneal (50 and 100 mg/kg/day) and oral (100 and 200 mg/kg/day) administration, respectively. The treatment with EOGF did not significantly affect body mass, macroscopy of the organs, or blood leukocyte counts. Based on these results, we can conclude that EOGF possesses significant antitumor activity and has only low systemic toxicity. These effects could be assigned to its components α-, β-, and γ-eudesmol.

Eudesmols are naturally occurring sesquiterpenoid alcohols that present cytotoxic effect to cancer cells. Herein, all eudesmol isomers displayed cytotoxicity to different tumour cell lines. a-Eudesmol showed IC 50 values ranging from 5.38 AE 1.10 to 10.60 AE 1.33 lg/mL for B16-F10 and K562 cell lines, b-eudesmol showed IC 50 values ranging from 16.51 AE 1.21 to 24.57 AE 2.75 lg/mL for B16-F10 and HepG2 cell lines, and c-eudesmol showed IC 50 values ranging from 8.86 AE 1.27 to 15.15 AE 1.06 lg/mL for B16-F10 and K562 cell lines, respectively. In addition, in this work, we studied the mechanisms of cytotoxic action of eudesmol isomers (a-, b-and c-eudesmol) in human hepatocellular carcinoma HepG2 cells. After 24-hr incubation, HepG2 cells treated with eudesmol isomers presented typical hallmarks of apoptosis, as observed by morphological analysis in cells stained with haematoxylin-eosin and acridine orange/ethidium bromide. None of eudesmol isomers caused membrane disruption at any concentration tested. Moreover, eudesmol isomers induced loss of mitochondrial membrane potential and an increase in caspase-3 activation in HepG2 cells, suggesting the induction of caspase-mediated apoptotic cell death. In conclusion, the eudesmol isomers herein investigated are able to reduce cell proliferation and to induce tumour cell death by caspase-mediated apoptosis pathways.Several studies have demonstrated that natural products and/or natural product structures continued to play a highly significant role in drug discovery and development process. In the case of approved therapeutic agents (01/1981-12/2010), only 20.2% of the total number of small-molecule anticancer drugs is classifiable into the synthetic category [1].Some studies have reported cytotoxic activity for plants belonging to the genus Guatteria of the Annonaceae plant family [2][3][4][5]. Our research group demonstrated that the leaf essential oil of Guatteria friesiana possesses in vitro and in vivo antitumour actions, without substantial systemic toxicity [5]. The main components identified in G. friesiana essential oil were eudesmol isomers (a-, b-and c-eudesmol; fig. 1 [15]. These three eudesmol isomers have been also reported previously as cytotoxic agents, displaying cytotoxicity to several human tumour cell lines [5,8,9,16,17]. Moreover, other plant species that contain eudesmol isomers also present cytotoxic activity [18,19]. In addition, Li et al. [20] reported that b-eudesmol induces c-Jun N-terminal kinases (JNK)-dependent apoptosis through the mitochondrial pathway in HL60 cells; however, the mechanism of cytotoxicity of aor c-eudesmol has not been investigated. Therefore, in the present work, we investigated the cytotoxic mechanism of eudesmol isomers (a-, b-and c-eudesmol) in human hepatocellular carcinoma HepG2 cells. Materials and MethodsEudesmols isolation. Guatteria friesiana leaves were collected at the Federal University of Amazonas (UFAM), Manaus, AM, Brazil, in January 2008. A voucher specimen (no. 7341) was deposited in the Herbar...

Guatteria blepharophylla Mart. (synonym Guatteriopsis blepharophylla Mart.) and Guatteria hispida (R.E. Fr.) Erkens & Maas (synonym Guatteriopsis hispida R.E. Fr.) belong to the Annonaceae family and are found in the Brazilian and Colombian Amazon basin. Both species are popularly known as ‘envira’ or ‘envireira’. In the present study, the leaf essential oils of G. blepharophylla (EOGB) and G. hispida (EOGH) were selected to investigate their cytotoxic effects. Tumour cell lines were treated with increasing concentrations of both essential oils for 72 h and analysed by a methyl‐[3H]thymidine incorporation assay. The pro‐apoptotic effect of these essential oils was assessed in HepG2 cells by morphological analysis (using haematoxylin/eosin staining and acridine orange/ethidium bromide staining), flow cytometry (cell membrane integrity and internucleosomal DNA fragmentation analysis) and a caspase‐3 activation assay after 24 h incubation. Both essential oils displayed potent cytotoxicity in different tumour cell lines. EOGB showed IC50 values from 6.03 to 16.46 µg/ml for HepG2 and K562 cell lines, and EOGH showed IC50 values from 5.45 to 24.89 µg/ml for HepG2 and K562 cell lines, respectively. Cell morphologies consistent with apoptosis and a remarkable activation of caspase‐3 were observed in the HepG2 cells treated with essential oils for 24 h. Significant increases in internucleosomal DNA fragmentation without altered membrane integrity were also found. In conclusion, both essential oils investigated were able to inhibit tumour cell proliferation and induce cell death by apoptosis pathways. Copyright © 2014 John Wiley & Sons, Ltd.

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