Detection of cytokinins and auxin in plant tissues using histochemistry and immunocytochemistry.

We report a new method for histochemical localization of cytokinins (CKs) in plant tissues based on bromophenol blue/silver nitrate staining. The method was validated by immunohistochemistry using anti-trans-zeatin riboside antibody. Indole-3-acetic acid (auxin, IAA) was localized by anti-IAA antibody in plant tissues as a proof for IAA histolocalization. We used root sections, because they are major sites of CKs synthesis, and insect galls of Piptadenia gonoacantha that accumulate IAA. Immunostaining confirmed the presence of zeatin and sites of accumulation of IAA indicated by histochemistry. The colors developed by histochemical reactions in free-hand sections of plant tissues were similar to those obtained by thin layer chromatography (TLC), which reinforced the reactive sites of zeatin. The histochemical method for detecting CKs is useful for galls and roots, whereas IAA detection is more efficient for gall tissues. Therefore, galls constitute a useful model for validating histochemical techniques due to their rapid cell cycles and relatively high accumulation of plant hormones.

Curcumin enhances the activity of fluconazole against Cryptococcus gattii-induced cryptococcosis infection in mice.

AIM: The aim of this study was to investigate the in vitro and in vivo activities of pure curcumin, as well as its combination with fluconazole, against Cryptococcus gattii. METHODS AND RESULTS: The minimal inhibitory concentrations (MIC) of curcumin and its interactions with fluconazole against C. gattii were assessed in vitro using standard methods. This same combination was used to treat C. gattii-induced cryptococcosis in mice. The behavioural and functional assessment of the mice during treatment was also performed. The average MIC for curcumin was 19·8 µg ml(-1) . Its combination with fluconazole resulted in FICΣ (fractional inhibitory concentration index) values between 0·79 and 2·29. Curcumin (alone or combined with fluconazole) significantly reduced pulmonary damage and fungal burden in the brain. No colonies were found in the brain following combination treatment, which was also confirmed by the improved behaviour of mice. CONCLUSIONS: The combination therapy with curcumin and fluconazole was the most effective among the treatments tested, as in addition to reducing the fungal burden and damage on lung tissues, it was able to eliminate the fungal burden in the brain, enhancing the survival of mice. SIGNIFICANCE AND IMPACT OF THE STUDY: This study points to the possibility of using curcumin in combination with fluconazole as a clinical treatment of cryptococcosis.

Hydroxyaldimines as potent in vitro anticryptococcal agents.

UNLABELLED: Cryptococcosis, a fungal infection that affects both immunocompromised and immunocompetent individuals, contributes to increasing indices of mortality and morbidity. The development of resistance by Cryptococcus spp., the limited number of commercial antifungal drugs and the various side effects of these drugs cause the treatment of cryptococcosis to be a challenge. The in vitro anticryptococcal activity of nine hydroxyaldimines was evaluated against 24 strains of Cryptococcus spp. Antifungal susceptibility was evaluated using a broth microdilution assay following the Clinical and Laboratory Standards Institute guidelines, using fluconazole as a positive control. Parameters such as the minimum inhibitory concentration and the minimum fungicidal concentration (MIC and MFC, respectively) were also determined. Antiproliferative activity on the normal cell line VERO was assessed 48 h post-compound exposure to determine the selectivity index (SI) of the hydroxyaldimines and fluconazole. All hydroxyaldimines were active against Cryptococcus spp. strains. Compounds 3A9 and 3B7 were the most potent against the Cryptococcus gattii and Cryptococcus neoformans strains. Selectivity indices also revealed that 3B10, 3C3, 3D3 and 3D9 are good candidates for in vivo studies. The in vitro anticryptococcal activity of hydroxyaldimines against various strains of C. gattii and C. neoformans indicates the potential of this class of molecules as lead compound for the development of selective and efficient anticryptococcal agents. SIGNIFICANCE AND IMPACT OF THE STUDY: The effectiveness of hydroxyaldimines for inhibition of Cryptococcus spp. growth and their low toxicity against healthy monkey kidney epithelial cells makes them promising lead compounds for the design of new anticryptococcal agents.

In vitro studies of anticandidal activity of goniothalamin enantiomers.

AIMS: The antifungal activity of (R)-goniothalamin (1) and (S)-goniothalamin (ent-1) was evaluated against six Candida species. The in vitro effect of these compounds on yeast adhesion to human buccal epithelial cells (BEC) and Candida albicans and C. dubliniensis biofilms progression were also investigated. METHODS AND RESULTS: Yeast susceptibility was evaluated by broth microdilution assay and showed that ent-1 exhibited higher potency against all fungal clinical isolated when compared to compound 1. Compounds 1 and ent-1 were as potent as fluconazole in inhibiting the adhesion of C. albicans and C. dubliniensis to BEC. XTT-reducing assay and scanning electron microscopy revealed that 1 and ent-1 were twice as potent as fluconazole in the inhibition of yeast biofilms progression. CONCLUSIONS: Our findings indicate that compounds 1 and ent-1 are potent anticandidal agents. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights goniothalamin enantiomers as promising lead compounds for the design of new antifungal with inhibitory activity on yeast adhesion and biofilm progression.

Curcumin as a promising antifungal of clinical interest.

OBJECTIVES: The antifungal activity of curcumin was evaluated against 23 fungi strains and its in vitro inhibitory effect on the adhesion of Candida species to human buccal epithelial cells (BEC) was also investigated. METHODS: The antifungal susceptibility was evaluated by broth microdilution assay following the CLSI (formerly the NCCLS) guidelines. The inhibitory effect of curcumin on the cell adhesion was performed with Candida species and BEC. RESULTS: Paracoccidioides brasiliensis isolates were the most susceptible to curcumin while the growth of Aspergillus isolates was not affected. Curcumin was much more efficient than fluconazole in inhibiting the adhesion of Candida species to BEC, particularly those strains isolated from the buccal mucosa of AIDS patients. CONCLUSIONS: The lack of antifungal compounds with reduced side effects highlights the importance of studying natural products for this purpose. Curcumin was a more potent antifungal than fluconazole against P. brasiliensis, the causal agent of the neglected disease paracoccidioidomycosis. Curcumin dramatically inhibited the adhesion of Candida species isolated from AIDS patients to BEC, demonstrating that curcumin is a promising lead compound that warrants further investigation into its therapeutical use in immunocompromised patients.

Styryl lactones and their derivatives: biological activities, mechanisms of action and potential leads for drug design.

Nature is an inexhaustible source of natural compounds with interesting biological activities. In general, natural products are an important source of new compounds with a variety of structural arrangements and singular properties. Styryl lactones are a group of secondary metabolites ubiquitous in the genus Goniothalamus that have demonstrated to possess interesting biological properties, in particular antiproliferative activity against cancer cells. In general, the cytotoxicity of styryl lactones appears to be specific against cancer cells since insignificant effects of these compounds on normal cells are reported. A large body of evidence suggests that the antiproliferative activity of styryl lactones is associated with the induction of apoptosis in target cells. In the first part of this review we discuss the biological activities of styryl lactones focusing on cancer cells, the causal agent of Chagas' disease and the vectors for yellow fever and human lymphatic filariasis. Stru described in detail for ninety styryl lactones. The last part describes the molecular targets of styryl lactones for inducing apoptosis, as well as immunosuppressive and inflammatory processes. Overall, understanding how these compounds exert their activities in biological system is essential for future development and application of styryl lactones for human health.