Antitumor Effect of Saffron (Crocus sativus L.): Overview and Perspectives

From ancient times, saffron dried stigmas of Crocus sativus L. is widely used as a drug against different human diseases. In the beginning of 1990 ́s scientific literature reported for the first time the antitumor activity of saffron. During the last decade different laboratories of the world (including ours) have accumulated sufficient scientific evidence to suggest that saffron, and its main ingredients, can inhibit the process of carcinogenesis in vivo and in vitro effectively. The aim of this work has been to summarize and discuss the scientific results obtained in our laboratory, together with data collected from the literature, about the antitumor and anticarcinogenic activities of saffron and its main ingredients, and the possible molecular mechanism of these actions. Saffron and its carotenoid ingredients are chemopreventive in cultivate human malignant cells and animal models, inhibiting cell growth. This could explain how they reduce outgrowth of tumor cells in vivo. It has been shown that those malignant cells are more sensitive than normal cells to the inhibitory effect of saffron. Inhibition of intracellular nucleic acid synthesis and free radical chain reactions may contribute to explain the molecular mechanism of antitumor effect of saffron. Although, it may be too soon to celebrate, the antitumor activity of saffron is quite promising and warrants further investigations, especially in clinical trials. INTRODUCTION Plant based natural products have been a fertile source of cure for cancer, which is projected to become the major causes of death in this century. There are at least 250,000 species of plants out of which more than one thousand plants have been found to possess significant anticancer properties (Abdullaev, 2001). Commercial saffron is derived from the stigmas of Crocus sativus L. a member of the Iridaceae family. The taxonomic classification of saffron is the following: Division: Spermatophyta Subdivision: Angiospermae Class: Monocotyledonae Subclass: Lilidae Order: Liliales Family: Iradaceae Genus: Crocus Characteristic ingredients of saffron (Figure1) are crocin –responsible of the color, picrocrocin –responsible of the bitter taste and safranal –responsible of the odor and aroma (Abdullaev, 1993). The use of saffron for medical benefit has played an important role in traditional medicine of different cultures on earth (Abdullaev, 1993). Anecdotal data comprise much of the popular information available about saffron in folklore medicine. In modern pharmacy saffron has reputed to be useful in treatment of numerous human diseases including cancer (Abdullaev, 2002a). The widespread use of saffron, either directly or as dietary supplement, has raised many scientific questions. One of them is, are saffron preparations safe? Animal studies indicated that oral LD50 of saffron, administered as a decoction, was 20.7 g/kg. Our data demonstrated that oral Proc. I IS on Saffron Eds: J.-A. Fernández & F. Abdullaev Acta Hort 650, ISHS 2004 492 administration of saffron at concentrations from 0.1 to 5 g/kg was nontoxic in mice (Abdullaev, 2002b). In the beginning of 1990 ́s scientific literature reported for the first time the antitumor activity of saffron (Nair et al, 1991; Abdullaev and Frenkel, 1992a,b). During the last decade, results of saffron antitumor research were published in 29 experimental articles and 8 review articles (Tables 1 and 2). It is a fact that saffron anticancer research clearly requires multinational efforts, involving scientists from Azerbaijan, Greece, Hungary, India, Japan, Mexico, Spain, USA and others. This review will focus on research findings, mainly from our laboratory, regarding the antitumor and anticarcinogenic activities of saffron and its main ingredients, possible molecular mechanism(s) of action(s) and perspectives in this area of research. ANTITUMOR EFFECTS OF SAFFRON AND ITS INGREDIENTS ON TUMOR CELLS IN VITRO Several of studies from our laboratory (Abdullaev and Frenkel, 1992a,b; Abdullaev, 1994; Abdullaev and González de Mejía, 1995; Abdullaev et al, 2002a,b, 2003a,b) have demonstrated the cytotoxic effect of saffron extract on different human normal and malignant cells in vitro (Table 3). Saffron extract had no effect on two normal human cell lines, but inhibited the growth of all tested human malignant cells (six) in dose-dependent manner. The most sensible to the inhibitory effect of saffron were A204 human rhabdomyosarcoma cells. It is interesting to note that saffron showed inhibitory effect of tested human malignant cells from different origin. Data presented in Table 4 indicate that saffron extract had no effect on macromolecular synthesis neither in normal or malignant human cells in vitro, but exhibited a dose-dependent inhibitory on nucleic acid synthesis in the tested malignant cells. No effect of saffron extract was observed on protein synthesis neither in normal or malignant cells. Commercial crocetin isolated from saffron had no cytotoxic effect on colony formation of normal and malignant human cells (Table 5). Our results demonstrated that crocetin inhibited synthesis of DNA, RNA and protein in dose-dependent manner only in malignant human cells. Data presented in Table 6 demonstrated inhibitory effect of different isolated carotenoid ingredients of saffron on colony formation of human HeLa cells. It was shown that trans-crocin-3, isolated from saffron, was more effective. It would be interesting to ascertain: Does saffron interact with other antitumor agents to enhance or reduce their efficacy? In other of our articles, presented in this volume (chapter 58), we have demonstrated that saffron in combination with a well known antitumor compound, sodium selenite, caused an additive inhibitory effect on four human malignant cells tested in vitro (Riverón-Negrete et al., 2004). The effect of saffron extract on viability on four human cells lines is presented in Table 7. Cell lines utilized in these experiments were SKNSH (malignant cells derived from a bone metastases of a neuroblastome), HeLa (malignant cells from an adenocarcinoma from uterine cervix), MCF-7 (malignant cells from a breast tumor), and normal fetal lung fibroblast cells. All the cells lines are of human origin, and they were obtained from ATCC (American Type Culture Collection). Saffron extract inhibited the viability of human malignant cells in dose dependent manner. IC50 for normal cells was about 10 times higher than for malignant cells. By using the Ames/Salmonella plate incorporation assay with five strains of these bacteria, both with and without S9 activation, no mutagenic activity of saffron extract up to concentration of 1500 μg/plate was detected (Table 8). The mutation index (MI) was less than 2, at all the tested concentrations of saffron extract. Previously, it was shown that saffron extract was non antimutagenic with benzo (a) pyrene (Abdullaev et al., 2003a). In Table 9 literature data on the cytotoxic effect of saffron and its ingredients on different malignant cells are summarize. Literature data about anticarcinogenic and antitumor effect of saffron in animal models has been discussed in a recent review (Abdullaev, 2002). Different hypothesis for the antitumor mechanism of action of saffron and its ingredients have been proposed, e.g. inhibition of intracellular DNA and RNA synthesis, inhibition of free radical chain reactions, stability to irradiation, metabolic conversion of carotenoids to retinoids, increase of intracellular SH-compounds, inhibition of