Although small molecule drugs (SMD) are still mainstream for the treatment of diseases, large molecule biologicss of many advantages, pose a challenge to the further discovery and use of SMD. The advantages of SMD are the convenience of oral administration and good patient compliance. However, the challenge with SMD is to integrate the PD, PK, selectivity and safety into a chemical structure. Because of their small size and surface area they often bind to various proteins, and off-target actions can cause adverse reactions. In this sense, selectivity is critical. Based upon target as the core to construct a chemical structure, it is necessary to consider the requirements of all the attributes, but achievement of the full-dimensional optimization is difficult. Modern drug discovery has been greatly enhanced by molecular biology and structural biology, and new strategies and technologies have emerged, which have created many successful medicines. For example, under the guidance of structural biology, covalent binding drugs connect moderate "electrophilic warheads" to the appropriate positions of molecules, and upon binding to their targets the electrophiles are irreversibly linked to the target by covalent bonds. Molecular biology can be directly applied to the development of antibody-coupled drugs (ADC). The antibody (A) acts as a carrier and a guide (for PK), and carries toxic molecules (D) into cancer cells, thus playing a killing role (for PD). The separate pharmacodynamic and pharmacokinetic entities are coupled (C) by linkers. PROTACs are also bifunctional molecules, which recruit a target protein and ubiquitin ligase E3 to form a ternary complex, which then acts as a catalyst to ubiquitinate the target protein and lead to degradation by the proteasome. In addition, in recent years, the combination of two fixed-dose drugs has improved selectivity, safety, and long-term benefit with many severe diseases, and can be regarded as an innovative strategy of physical combination. This review discusses some successful examples to briefly present the principles from the perspective of medicinal chemistry and therapeutic application.

There is a variety of gut microbiota in human body, which is closely associated with the health and disease. Normal gut microbiota can produce colonization resistance to pathogens. Antibiotics can affect the composition of gut microbiota and change the intestinal microenvironment, resulting in intestinal microecological disorders, which in turn cause intestinal pathogenic infections and other diseases. In this paper, the concept of intestinal microecology, the mechanism of intestinal colonization resistance, the effect of antibiotics on intestinal microecology, and the treatment methods were reviewed, aiming to provide the information for the rational use of antibiotics and the development of more effective treatment methods to maintain the stability of intestinal microecology.

Cardiovascular disease (CVD) is a major contributor to patient deaths worldwide, and its pathogenesis is complex and mortality rates are increasing every year. Numerous researches have shown that the gut microbiota and its metabolites were closely associated with the development of CVD, and gut microbiota was expected to be a potential new target for the treatment of CVD. Traditional Chinese medicine (TCM), characterized by its multi-component, multi-target and integrity, can play a therapeutic role in CVD by regulating the gut microbiota, which has obvious advantages in stabilizing the disease, improving heart function and enhancing quality of life, and is an ideal intestinal microecological regulator. Therefore, this review will mainly discuss the intimate association of gut microbiota and its metabolites with CVD, and the therapeutic strategies of TCM targeting gut microbiota to improve CVD, including regulating the composition of gut microbiota, protecting the intestinal mucosal barrier, influencing the intestinal immune function and modulating the metabolites of gut microbiota, in order to provide a reference for the research of TCM targeting gut microbiota for CVD.

Small molecule fluorescent probes have gained widespread attention for their advantages of high selectivity, sensitivity, and easy to operate, and have played a critical role in the detection of various species. They have also demonstrated great potential in the field of biomedical research. Iron, as the most abundant transition metal in the human body, plays a vital role in many physiological functions. Due to the influence of the reductive microenvironment of cell, ferrous ion (Fe²⁺) is the main component of labile iron in living cells. Heme, consisting of Fe²⁺ and protoporphyrin IX, is one of the main signaling molecules that wrap biological iron in the human body, and also participates in many physiological and pathological processes. Therefore, the development of small molecule fluorescent probes for detecting Fe²⁺ and heme as effective monitoring tools will help to further understand their pathological and physiological functions, with potential applications in other fields. This review summarizes the research progress of small molecule fluorescent probes for Fe²⁺ and heme detection in recent years, and provides insights into future directions for their development.

Target identification and verification of natural products is an important and challenging work in the field of chemical biology. It is also an important job for researchers to apply chemical proteomics technology to biomedicine in order to identify target proteins of natural products. Target identification is critical to understanding its mechanisms and developing natural products as molecular probes and potential therapeutic drugs. Traditional approaches of small molecule target identification based on affinity have been shown to be successful, such as click-chemical probes, radioisotope labeling or photosensitized small-molecule probes. Nevertheless, these technologies require purified candidate target proteins, and modified small molecules with probes or linkers, such as adding agarose beads, biotin labels, fluorescent labeling or photo-affinity labeling. Many structure-activity relationship studies should be performed to ensure that the addition of small molecule labels undisturbed the original biological activity of the small molecules. Unfortunately, all these modifications are likely to alter their biological activity or binding specificity. To overcome the bottleneck of "target recognition", researchers have developed a series of new techniques for unmodified drug target identification. In this article, we reviewed the target identification techniques of natural product without structural modification in order to provide reference for the development of natural products.

Toll like receptors (TLRs) are the earliest discovered natural immune pattern recognition receptors (PRRs). The abnormality of TLR signal transduction pathway is the key factor leading to chronic inflammatory, cancer, nervous system disease and cardiovascular diseases. The development of TLR agonists and inhibitors has attracted much attention. Currently known TLR2 agonists, such as lipopeptides or their derivatives, have certain limitations in drug development due to their difficult synthesis, easy hydrolysis, and triggering inflammatory cytokine storms, while inhibitors have been rarely reported. New small molecule TLR2 agonists or inhibitors with higher stability are more likely to be developed as tumor immunotherapy or anti-inflammatory drugs.

Autophagy often occurs after cells are attacked by oxidative stress, where damaged structures are phagocytic and degraded into nutrients, thereby reducing oxidative damage, promoting the survival of cancer cells and reducing the therapeutic effect of photodynamic therapy (PDT). However, excessive activation of autophagy can promote cell apoptosis. In this paper, the photosensitizer pyropheophorbide-a (Ppa) was used to produce a large amount of reactive oxygen species (ROS) to achieve the effect of killing cancer cells. At the same time, icaritin (Ica), an autophagy inducer, was used to over-activate autophagy, which transformed the protection of cancer cells into the promotion of cancer cell apoptosis, so as to improve the effect of photodynamic therapy. In this study, the interaction force between Ica and Ppa was exploited to successfully construct a self-assembled nanomedicine IP with good stability and high drug load. The synthesis method is simple, through using the drug itself as a carrier, and the loading capacity (LA) of Ica and Ppa can be increased to 83.53% and 16.45% without introducing potential biosafety risks of nanocarriers. Compared with free Ppa, self-assembled nanomedicine IP showed superior performance in cellular uptake and reactive oxygen species production. In addition, the self-assembled nanomedicine IP can reverse the protective autophagy induced by PDT by activating the autophagy of tumor cells, and facilitate apoptosis and antitumor coordination, which significantly improves the antitumor activity of PDT.

The trace chemical components in functional Monascus rice were studied to explore the potential bioactive substances. MCI column, Sephadex LH-20 gel, and preparative liquid chromatography were used to purified the ethyl acetate extract from functional Monascus rice. Two novel pyridine Monascus pigments were isolated and identified, named monascopyridine G (1) and monascopyridine H (2), respectively based on extensive mass spectrometry (MS), infrared radiation (IR), and nuclear magnetic resonance (NMR) analysis. The molecular docking experiments between compounds 1 and 2 and peroxisome proliferators-activated receptor-gamma (PPARγ) showed that they exhibited obvious binding force with the receptor protein. Besides, the biosynthetic pathways of the two compounds were proposed, which provide a valuable reference for the selective production of these potential bioactive substances.

Cancer seriously threatens human life and health, it is urgent for the development of rapid detection, precise localization and effective treatment of tumors. Chemical fluorescent probes that are sensitive to tumor-specific microenvironments have important significance in tumor theranostics and a variety of such probes have been developed. In this review, we classified chemical fluorescent probes that are sensitive to tumor microenvironments according to biological characteristics and microenvironmental changes while combining spectroscopy or response mechanisms, and systematically introduced the research progress of chemical fluorescent probes with sensitivity to hypoxia, low polarity, high viscosity, abnormal pH values and abundant reactive oxygen species in tumor microenvironments, in order to provide references for the development and applications of these probes.

G protein-coupled receptors (GPCRs) represent the largest family of membrane proteins and are the target of approximately half of all therapeutic drugs. There are ~300 orphan GPCRs, which have great potential in drug development. G protein-coupled receptor 35 (GPR35), a rhodopsin-like orphan GPCR, is widely involved in immune regulation, gastrointestinal disorders, cardiovascular diseases, cancer, as well as other diseases, suggesting its great potential as a therapeutic target in a variety of diseases. However, the current research on GPR35 is insufficient, including the true endogenous ligand has not been confirmed, the molecular mechanism of its role in disease is not fully understood, and there is a lack of effective intervention strategies targeting GPR35. This article summarizes the deorphatization of GPR35, GPR35-related signaling pathways and their association with various diseases, in order to provide a reference for in-depth study of GPR35 in diseases and development of drugs targeting GPR35.