Francisco Coll

Influence of Brassinosteroids on Antioxidant Enzymes Activity in Tomato Under Different Temperatures

The effect of brassinosteroids (BRs) on catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) activity in tomato leaf discs was analyzed at 25 and 40 °C. Tomato leaf discs were preincubated for 24 h in Petri dishes with 24-epibrassinolide (EBR) or a polyhydroxylated spirostanic analogue of brassinosteroids (MH5). Both concentrations (10.60 and 2.12 nM) of EBR and MH5 stimulated the activity of SOD at 25 and 40 °C, the MH5-stimulated increase of this enzyme activity was greater. Peroxidase activity was unaffected at 25 °C, while at 40 °C this activity was enhanced by both compounds. The changes in catalase activity markedly depended on the structure BRs, doses and temperature. The results suggest a possible role of EBR and MH5 in the reduction of cell damage produced by heat stress due to induction of enzymatic antioxidants.

Effects of brassinosteroid analogues on total phenols, antioxidant activity, sugars, organic acids and yield of field grown endive (Cichorium endivia L.).

BACKGROUND Cichorium endivia L., either cooked or eaten raw in salads, is a favourite cultivated vegetable around the world and the popularity is attributed to its healthy properties, which are mainly due to its high levels of antioxidant compounds and high content of minerals, provitamin A and vitamins. Brassinosteroids are a family of hormones that are found in plants and which serve as potent growth promoters. The effects of two brassinosteroid analogues, DI-31 and DI-100, were evaluated at concentrations of 4, 8 and 12 ppm together with a seaweed extract and amino acid mixture called Tomex Amin to enhance their activity. RESULTS All treatments with DI-100 and DI-31 resulted in the highest production increases. The chemical variables related to endive quality, such as moisture, carbon and nitrogen content, sugar and organic acid content were similar in the control and treated endives. Total antioxidant activity and total phenols increased significantly in endive treated with brassinosteroid analogues. CONCLUSION The results showed that sprayed brassinosteroid analogues mixed with Tomex Amin may play an important role in increasing the yield and the contents of total antioxidant activity and total phenols of field grown endives.

Studies on the regioselectivity of the baeyer-villiger reaction of 3-keto steroids : Conformational effects determine the migration aptitude

A detailed study of the Baeyer-Villiger reaction of 3-ketosteroids has been performed by using m-chloroperoxybenzoic and trifluoroperoxyacetic acids as oxidants. The process was fully regiospecific for 3-keto-5alpha-steroids with the employ of both peracids, and only partially regioselective for 3-keto-5beta-steroids by using trifluoroperoxyacetic acid. Interestingly, the reaction resulted completely unselective for 3-keto-5beta-steroids by using m-chloroperoxybenzoic acid. Theoretical studies were performed to explain the regiochemistry of this process, which is suggested to be controlled by conformational effects in the transition state of the Criegee rearrangement.

Effects of structural analogs of brassinosteroids on the recovery of growth inhibition by a specific brassinosteroid biosynthesis inhibitor

A brassinosteroid inhibitor (Brz2001) was used to block the growth of roots, hypocotyls, and epicotyls of soybean seedlings, producing a dwarf phenotype. The application of 24-epibrassinolide completely reversed the inhibitory effects of Brz2001. Two other growth-promoting brassinosteroid analogs, MH5 and BB6, partially overcame the Brz2001-induced growth defects. The growth inhibition of Brz2001-treated seedlings was more effectively reversed by MH5 than by BB6, which may be due to the structural differences between the two compounds. These results indicate that the studied analogs may show brassinosteroid-like activity and therefore may have some practical use instead of brassinolide or its analogues.

Synthesis of New Pyrazole and Pyrimidine Steroidal Derivatives

The synthesis of steroidal heterocycles containing the pyrazole and pyrimidine ring fused to the 16,17-position of the steroid nucleus is reported. Androstenolone acetate (1) reacted with carbon disulfide, iodomethane and sodium hydride to furnish 3β-acetoxy-16-[bis(methylthio)methylene]-5-androst-5-en-17-one (2). The reactions of 2 with hydrazine hydrate and methylhydrazine afforded the 5’-methylthio- pyrazolo[4’,3’:16,17]androst-5-en-3β-ols 3a and 3b, respectively. Treatment of 2 with amidinium, guanidinium, and isothiuronium salts in the presence of sodium methoxide yielded the 6’-methoxy- pyrimido[5’,4’:16,17]androst-5-en-3β-ols (4a-4e).

Brassinosteroids roles and applications: an up-date

Abstract Brassinosteroids are plant steroidal compounds involved in many functions related with plant development, metabolism, signalling and defense against a wide range of biotic and abiotic stresses. Plant architecture, which has a major effect on crop yield, is strongly influenced by brassinosteroids action. Brassinosteroids are recognized as key regulators of plant growth and development involved in a broad spectrum of processes at the molecular, cellular, and physiological levels. These roles suggest that many of the constraints of present agricultural production might be alleviated by manipulation of genetic determinants dealing with brassinosteroids, as well as by its exogenous application. Brassinosteroids are natural, nontoxic, non-genotoxic, biosafe, and eco-friendly, and can therefore be used in agriculture and horticulture to improve the growth, yields, quality, and tolerance of various plants to biotic and abiotic stresses. The present paper comprehensively reviews the latest results in the field of brassinosteroids and envisages future impacts in agriculture.

Effects of a brassinosteroid analogue to mosquito larvae.

Many plant compounds are able to modulate herbivore growth and reproduction by directly interacting with steroid hormones systems. In insects, several classes of phytochemicals, including brassinosteroids and related substances, interfere with molting and reproduction. The effects of the molting-hormone antagonist pesticide DI-31, a brassinosteroid analogue, on Aedes aegypti mosquito larvae were tested in two different exposure scenarios. After static exposure of first-instar larvae, the calculated NOEC, LOEC, and LC(50) values referenced to 19 d were 0.03, 0.036, and 0.04 mg/mL, respectively. Semistatic exposure of fourth-instar larvae revealed them to be slightly less susceptible than the younger larvae (NOEC 0.03 mg/mL, LOEC 0.036 mg/mL, LC(50) 0.049 mg/mL referenced to 19 days). In both cases mortality was immediate and larval development was retarded. This study suggests that A. aegypti could be a useful model for the detection of hormonally active substances such as DI-31.

Synthesis and Plant Growth-Activity of three New Brassinosteroids Analogues

Abstract The chemical synthesis, starting from deoxycholic acid methyl ester, of several brassinosteroids analogues with different oxygenated functions in ring C, is described. Three of them showed growth-promoting activity