Botanical and biological pesticides elicit a similar Induced Systemic Response in tomato (Solanum lycopersicum) secondary metabolism.

Natural pesticides have attracted substantial interest due to the increase in organic agriculture and enhanced attention to environmental pollution. Plant Growth Promoting Bacteria (PGPB) are applied for both disease control and growth enhancement; PGPBs are known to elicit Induced Systemic Response (ISR) in plants. However, less is known about the effect of botanical pesticides, such as the azadirachtin-containing neem extracts, on plant metabolism. This study aimed to investigate the effects of foliar application of the above-mentioned natural pesticides on the metabolic profiling of tomato. Leaf application of Bacillus subtilis fostered Induced Systemic Resistance (ISR) in treated plants via the Jasmonic acid pathway, and enhanced production of secondary metabolites such as flavonoids, phytoalexins and auxins. Changes in sterols and terpenes, as well as an increase in glucosinolates were also observed. Interestingly, azadirachtin-treated tomatoes also showed an increase in ISR and our results revealed that most of the enriched metabolites are shared with a B. subtilis treatment, suggesting conserved biochemical responses. These (un)expected findings indicate that plants are not insensitive to application of natural pesticide and while Azadirachtin is applied as a direct pesticide, it also stimulates a defense response in tomatoes very similar to B. subtilis induced ISR.

Structure-activity relationship and role of oxygen in the potential antitumour activity of fluoroquinolones in human epithelial cancer cells.

The photobehavior of ciprofloxacin, lomefloxacin and ofloxacin fluoroquinolones was investigated using several in vitro methods to assess their cytotoxic, antiproliferative, and genotoxic potential against two human cancer cell lines. We focused our attention on the possible relationship between their chemical structure, O2 partial pressure and photobiological activity on cancer cells. The three molecules share the main features of most fluoroquinolones, a fluorine in 6 and a piperazino group in 7, but differ at the key position 8, unsubstituted in ciprofloxacin, a fluorine in lomefloxacin and an alkoxy group in ofloxacin. Studies in solution show that ofloxacin has a low photoreactivity; lomefloxacin reacts via aryl cation, ciprofloxacin reacts but not via the cation. In our experiments, ciprofloxacin and lomefloxacin showed a high and comparable potential for photodamaging cells and DNA. Lomefloxacin appeared the most efficient molecule in hypoxia, acting mainly against tumour cell proliferation and generating DNA plasmid photocleavage. Although our results do not directly provide evidence that a carbocation is involved in photodamage induced by lomefloxacin, our data strongly support this hypothesis. This may lead to new and more efficient anti-tumour drugs involving a cation in their mechanism of action. This latter acting independently of oxygen, can target hypoxic tumour tissue.

The resveratrol analog 4,4'-dihydroxy-trans-stilbene suppresses transformation in normal mouse fibroblasts and inhibits proliferation and invasion of human breast cancer cells.

4,4'-dihydroxy-trans-stilbene (DHS) is a synthetic analog of resveratrol, a phytoalexin known for its biological activities. We previously demonstrated that DHS exerts an antiproliferative effect on normal human fibroblasts that is higher than that of the natural parent molecule. No evidence regarding its role in human cancer cell lines has been found thus far. In this study, we investigated the effects of DHS both on chemical-induced transformation of BALB/c 3T3 mouse fibroblasts and on the proliferation and invasion of human breast cancer MCF-7 cells. The results showed that DHS markedly suppresses the two-stage (3-methylcholanthrene plus 12-O-tetradecanoylphorbol-13-acetate) cell transformation. Compared with resveratrol, DHS inhibited both anchorage-dependent and -independent MCF-7 growth more efficiently. In addition, a reduction in the number of cells in S-phase, characterized by a concomitant increase in the levels of p21 and p53 proteins, together with a strong inhibition of pRb protein phosphorylation, was observed in DHS-treated cells. Furthermore, DHS effected a strong reduction in matrix metalloproteinase-2 and -9 activities, concomitantly with a marked inhibition of cell adhesion to the extracellular matrix components as well as inhibition of cell migration and invasion. Importantly, modulation of the adhesion molecule E-cadherin was also found in DHS-treated cells. Taken together, these results demonstrate that the two 4,4'-hydroxyl groups on the stilbenic backbone make DHS a more active molecule than resveratrol in inhibiting neoplastic transformation, cancer cell proliferation and invasion. In conclusion, this study suggests that DHS could be a promising anticancer agent.