**Preface to "Natural Products and Derivatives in Human Disorders"**

When the *Molecules* Editorial Office proposed to us the idea of coordinating the edition, as Academic Editors, of a Special Issue related to our research experience carried out during the last twenty-five years, we were tremendously attracted to the possibility of being able to make a monographic book related to the bioactive role of different natural compounds from the kingdoms of plants and fungi, as well as many of their chemical derivatives, in the solution of a wide group of human disorders and pathologies. After deep reflection and after rejecting several titles, we decided to title it "Natural Products and Derivatives in Human Disorders".

This Special Issue was finished forging with the intention of requesting, collecting and disseminating some of the most significant and recent contributions in the use of natural compounds and derivatives to reduce the risk of developing inflammatory and oxidant diseases such as cancer and others human disorders.

Natural products are bioactive compounds synthesized by terrestrial and marine plants, fungi, microorganisms and animals. Traditionally, they have been used in the prevention and treatment of various human diseases in different cultures. In parallel, chemical derivatives of these natural compounds have been used in order to enhance their bioactivities.

Although numerous nitrogenous compounds present in the composition of all living organisms such as amino acids, nucleotides, biogenic amines, purine and pyrimidine bases and many others play an important role in their own development and survival [1,2], it is an authentic reality that scientists have recognized, for more than 50 years, that the wealth of secondary products also recognized as phytochemicals in the plant kingdom in secondary products, is much greater when compared to those found in the animal kingdom.

As we noted before [3,4], at the dawn of the 19th century, numerous researchers isolated and characterized, from a chemical point of view, numerous secondary products in different groups of plants that they called phenols, isoprenoids and alkaloids capable of presenting a real physiological and biochemical activity whose initial purpose was that of defense against different types of external aggressions caused by herbivores, competitors, pathogens and predators, avoiding, on the one hand, recurrent infections caused by parasites, bacteria and viruses, and on the other hand, the destruction of the organism produced by different types of phytophagous and mycophagous [5]. Later, from the 40s and 50s of the previous century, and with the advance of analytical techniques and methodologies, more than 5000 secondary products could be recognized and characterized, a number that nowadays exceeds, by far, 100,000 compounds [6].

During the last ten years, most of them have been reported to have a variety of interesting and significant biological properties, such as analgesic, anti-allodynic, anti-diabetic, anti-oxidant, anti-parasitic, antimicrobial, anti-viral, anti-atherogenic, anti-inflammatory, anti-proliferative, anti-tumour, growth-stimulating activities, as well as cardio and neuro-protective activities [7-11]. However, special attention has been focused on the study of their anti-tumour capacity, through the potential modulation of cancer initiation and growth, cellular differentiation, apoptosis and autophagy, angiogenesis, and metastatic dissemination. Moreover, a considerable number of studies reported the relation of the anticancer effect with their anti-inflammatory and antioxidant activities. Besides these capacities, the use of natural compounds and derivatives represent one of the most promising strategies to treat metabolic disorders such as oxidative stress, diabetes, obesity, metabolic syndrome, and so on [12-16].

The topics included in this Special Issue are:

·New natural compounds and derivatives as anticancer agents.

·Use of natural compounds and derivatives as anti-inflammatory agents in human disorders.

·Natural products and derivatives in oxidative stress associated with human diseases.

·Molecular mechanism implicated of natural products and derivatives.

·Effects of natural products and derivatives on nutrition and diet on human diseases.

·Type of natural product and derivatives with potential bioactive, extraction and synthesis.

After a relatively long period of requests for contributions, we decided to choose, from a total of more than 30 papers submitted, the seven contributions that passed the peer review and in which more than twenty independent reviewers participated. Finally, this book compiles a total of one editorial and seven original articles in which different phytochemicals and chemical derivatives are used, delving into the study of the molecular roles they present in different human pathologies, such as cancer, neuronal and ocular dysfunctions, arterial hypertension and osteoarthritis.

The different contributions presented in this book have been made by 55 authors of up to six nationalities (Korea, Spain, Germany, China, United Arab Emirates and Oman). The topics covered include situations that alter pathological growth processes of the liver, colon and breasts, with situations related to neurodegenerative diseases through inhibitors of acetyl and butyrylcholinesterases, and with alterations of the vascular, bone and ocular systems such as hypertension, osteoarthritis and dry eye disease, also known as keratoconjunctivitis.

The academic editors of this work thank the MDPI editorial group for this scientific space that it offers us and that serves to share with its future readers the feelings generated by the compilation of the different works that make up this work. We also want to congratulate all the participating authors, all the reviewers who without their work make it difficult for science to continue advancing and all the scientific and administrative staff of the *Molecules* Editorial Office for their extraordinary and excellent work. Finally, our special wish is that we all enjoy your reading.

#### **References**

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> **Eva E. Rufino-Palomares, Jos´e Antonio Lupi´a ˜nez** *Editors*
