Letícia Veras Costa-Lotufo

Erythrina verna, popularly known as “mulungu”, is a Brazilian medicinal plant used to treat anxiety. Erythrina alkaloids have been described in several species of Erythrina, which have biological and therapeutic properties well known that include anxiolytic and sedative effects.

Croton regelianus Muell. Arg., popularly known as ‘velame‐de‐cheiro’, is a native plant from the Northeast of Brazil used in folk medicine to treat diseases of different kinds, including malignant tumors. In this study, the in vitro and in vivo antitumor effects of the essential oil from the leaves of C. regelianus and ascaridole, one of the main constituents, were investigated. In vitro, the essential oil and ascaridole displayed cytotoxicity, showing IC₅₀ values in the range of 22.2 to 48.0 μg/ml in HL‐60 and SF‐295 cell lines for the essential oil, and 6.3 to 18.4 μg/ml in HL‐60 and HCT‐8 cells lines for ascaridole, respectively. The in vivo study, using sarcoma 180 as a tumor model, demonstrated inhibition rates of 28.1 and 31.8% for essential oil, at the 50 and 100 mg/kg, while ascaridole inhibition rates were 33.9% at 10 mg/kg and 33.3% at 20‐mg/kg doses. Histopathological examination showed that the organs were only weakly affected by the treatment. In conclusion, ascaridole has an interesting antitumor activity in sarcoma 180 murine model, probably related to the described cytotoxic activity, and, moreover, its presence in the essential oil from the leaves of C. regelianus could explain, at least in part, the ethnopharmacological use of this plant in the treatment of cancer.

Two lipidic α-amino acids 1a and 1b were isolated from the zoanthid Protopalythoa variabilis using a bioguided fractionation for cytotoxic activity. The structures of the metabolites were determined by spectroscopic methods, including NMR (nuclear magnetic resonance) ¹H e 13C, IR (infrared) and high resolution mass spectrometry (positive mode). The cytotoxic activity of the crude extract, as well as of the mixture of 1a and 1b were measured in vitro using the MTT assay for four human tumor cell lines. This finding has important biological and chemical implications for this type of compound. This is the first report of lipidic α-amino acids from natural sources, as well as of their cytotoxic activity.

Though sharing only a short part on the natural products timeline, the studies on marine products has already handed in four new drugs to the clinical arsenal and brought up a long and promising list of unique molecules to pre-clinical and clinical trials. Thus, as the available analytical resources improve and the interest of large pharmaceutical companies arises, medical use of marine products has definitely become a reality

Agaricus blazei Murrill, a native mushroom of Brazil, has been widely consumed in different parts of the world due to its anticancer potential. This effect is generally attributed to its polysaccharides; however, the precise structure of these has not been fully characterized. To better understand the relationship between polysaccharide structures and antitumor activity, we investigated the effect of the intraperitoneally (i.p.) or orally (p.o.) administered α-(1 → 4)-glucan–β-(1 → 6)-glucan-protein complex polysaccharide from A. blazei alone or in association with 5-fluorouracil (5-FU) in tumor growth using Sarcoma 180 transplanted mice. Hematological, biochemical, and histopathological analyses were performed in order to evaluate the toxicological aspects of the polysaccharide treatment. The polysaccharide had no direct cytotoxic action on tumor cells in vitro. However, the polysaccharide showed strong in vivo antitumor effect. Thus, the tumor growth-inhibitory effect of the polysaccharide is apparently due to host-mediated mechanisms. The histopathological analysis suggests that the liver and the kidney were not affected by polysaccharide treatment. Neither enzymatic activity of transaminases (AST and ALT) nor urea levels were significantly altered. In hematological analysis, leucopeny was observed after 5-FU treatment, but this effect was prevented when the treatment was associated with the polysaccharide. In conclusion, this polysaccharide probably could explain the ethnopharmacological use of this mushroom in the treatment of cancer.

In recent years, much attention has been focused on polysaccharides isolated from natural sources. The aim of this study was to investigate the in vitro and in vivo antitumor properties of a sulfated polysaccharide isolated from the seaweed C. feldmannii (Cf‐PLS). Hematological, biochemical and histopathological analyses were performed in order to evaluate the toxicological aspects related to Cf‐PLS treatment. Its effects on the immunological system were also investigated. The Cf‐PLS did not show any significant in vitro cytotoxicity at the experimental exposure levels that were used, but showed in vivo antitumor effect. The inhibition rates of sarcoma 180 tumor development were 48.62 and 48.16% at the doses of 10 and 25 mg kg⁻¹, respectively. In addition, Cf‐PLS was also able to increase the response elicited by 5‐fluorouracil (5‐FU) from 48.66 to 68.32%. The histopathological analysis of liver and kidney showed that both organs were moderately affected by Cf‐PLS‐treatment. Neither enzymatic activity of alanine aminotransferase nor urea or creatinine levels were significantly altered. In hematological analysis, leucopeny was observed after 5‐FU treatment, but this effect was prevented when the treatment was associated with the Cf‐PLS. It was also demonstrated that Cf‐PLS acts as an immunomodulatory agent, raising the production of specific antibodies, and increasing the production of OVA‐specific antibodies. It also induced a discreet hyperplasia of lymphoid folicules of the white pulp in the spleen of treated mice. In conclusion, Cf‐PLS has some interesting anticancer activity that could be associated with its immunostimulating properties. Copyright © 2008 John Wiley & Sons, Ltd.