Molecular Hybridization is an approach in rational drug design where new chemical entities are obtained by combining two or more pharmacophoric units from different bioactive compounds into a single molecule. Through this approach, medicinal chemists hope that the new hybrid derivative presents: better affinity and efficacy when compared to the parent drugs; a modified selectivity profile with improvement over pharmacokinetic and pharmacodynamic restrictions; dual or multiple modes of action; reduction of undesirable side effects; decreases in drug-drug interactions; reduced emergence or spread of drug resistance in microorganisms and protozoans; and lower cost. The approach has been successfully used by many research groups around the world and has had very promising results with diseases having multifactorial profiles, like Alzheimer´s, Parkinson´s disease, cancer, inflammation, and hypertension among others. The purpose of this paper is to conduct an updated review of molecular hybridization and multitarget profiling (a rational drug design approach), and its applications to the design and discovery of novel hybrid compounds with anti-inflammatory, antimicrobial, anticancer and antiprotozoal (leishmaniasis, malaria, and schistosomiasis) activities over the last six years.

The termneglected diseasesrefers to a group of infections caused by various classes of pathogens, including protozoa, viruses, bacteria, and helminths, most often affecting impoverished populations without adequate sanitation living in close contact with infectious vectors and domestic animals. The fact that these diseases were historically not considered priorities for pharmaceutical companies made the available treatments options obsolete, precarious, outdated, and in some cases nonexistent. The use of plants for medicinal, religious, and cosmetic purposes has a history dating back to the emergence of humanity. One of the principal fractions of chemical substances found in plants are essential oils (EOs). EOs consist of a mixture of volatile and hydrophobic secondary metabolites with marked odors, composed primarily of terpenes and phenylpropanoids. They have great commercial value and were widely used in traditional medicine, by phytotherapy practitioners, and in public health services for the treatment of several conditions, including neglected diseases. In addition to the recognized cytoprotective and antioxidative activities of many of these compounds, larvicidal, insecticidal, and antiparasitic activities have been associated with the induction of oxidative stress in parasites, increasing levels of nitric oxide in the infected host, reducing parasite resistance to reactive oxygen species, and increasing lipid peroxidation, ultimately leading to serious damage to cell membranes. The hydrophobicity of these compounds also allows them to cross the membranes of parasites as well as the blood-brain barrier, collaborating in combat at the second stage of several of these infections. Based on these considerations, the aim of this review was to present an update of the potential of EOs, their fractions, and their chemical constituents, against some neglected diseases, including American and African trypanosomiasis, leishmaniasis, and arboviruses, specially dengue.

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Flavonoids are phenolic compounds, secondary metabolites of plants that cause several benefits to our health, including helping the treatment against cancer. These pharmacological properties are associated with the ability of flavonoids in attenuating the generation of reactive oxygen species, acting as chelate compounds or affecting the oxi-redox cycle. In spite of the large number of information in term of SAR and QSAR, no recent review has tabulated and discussed in detail these data. In view of this, we bring here a detailed discussion of the structure-activity relationships (SAR) and quantitative structure-activity relationships (QSAR) models. We have also analyzed the correlation between the chemical structure of flavonoids and analogues to their anticancer activities. A large number of methodologies have been used to identify the characteristics of these compounds with their potential anticancer: multiple linear regression, principal components analysis, comparative molecular field analysis, comparative molecular similarity indices analysis, partial least squares, neural networks, configuration of classification and regression trees, Free-Wilson, docking; using topological, structural and enthalpies' descriptors. We also discussed the use of docking models, together with QSAR models, for the virtual screening of anticancer flavonoids. The importance of docking models to the medicinal chemistry of anticancer flavonoids has increased in the last decade, especially to help in identifying the structural determinants responsible for the activity. We tabulated here the most important examples of virtual screening determined for anticancer flavonoids and we highlighted the structural determinants. The mode of action, the most potent anticancer flavonoids and hints for the structural design of anticancer flavonoids are revised in details and provided here.

Natural products are compounds that are isolated from plants, provide a variety of lead structures for the development of new drugs by the pharmaceutical industry. The interest in these substances increases because of their beneficial effects on human health, which include antiviral, antiallergic, antiplatelet, anti-inflammatory, antitumor, antioxidant, and antiparasitic activities. Leishmaniasis is the infection caused by protozoa of the genus Leishmania, which affects mainly people who live in poor countries, and can cause chronic fever, liver problems, anemia, and other blood problems. Current chemotherapies against the disease cause side effects, and are ineffective. There are no vaccines, and new chemotherapeutic agents for the treatment of leishmaniasis are greatly needed. This work reports on some of the enzymatic targets studied in the development of new drugs using natural products as inhibitors for the treatment of leishmaniasis. We applied ligand-based-virtual screening using Random Forest, associated with structure-based-virtual screening (docking), of a small dataset of 683 flavonoids and derivatives from an in-house data bank to select structures with potential inhibitory activity against pyruvate kinase, an important enzyme in Leishmania mexicana's energy production chemistry. The computer-aided drug design studies revealed good results against Leishmaniasis for flavones.