Peptides constitute an important component of Nature’s pharmacy and they play a significant role in several signaling pathways acting as natural biological messengers. While nature has mastered the cycle of creation, application, and destruction of large and short peptides to the benefit of the host organism, organic and medicinal chemists have in their capacity and small steps, made big developments in the field of peptide synthesis as well as in developing them as therapeutics. In comparison to their big counterparts, i.e. proteins, short peptides encompass several advantages, from the ease of synthesis to their physico-chemical properties. However, the real challenge for in vivo application of therapeutic peptides is to overcome their low plasma availability and their fast enzymatic degradation. This review briefly covers the relevant areas of medicinally important short peptides and the recent developments made to turn these peptides into therapeutics. Also presented in this article are important efforts and strategies used to overcome some of the inherent limitations of peptidic molecules and thereby facilitate their progression in the clinical phases towards approved drugs.

It is widely acknowledged that sialyl Lewis X (sLeX), the composition and linkage of which are N-acetylneuraminic acid (Neu5Ac) α2-3 galactose (Gal) β1-4 [fucose (Fuc) α1-3] N-acetylglucosamine, is usually attached to the cell surface. It presents as a terminal structure on either glycoproteins or glycolipids and has been demonstrated to be related to various biological processes, such as fertilization and selectin binding. Due to the vital role of sLeX, its synthesis as well as its determination approaches have attracted considerable attention from many researchers. In this review, the focus is sLeX on glycoproteins. The biological importance of sLeX in fertilization and development, immunity, cancers, and other aspects will be first introduced. Then the chemical and enzymatic synthesis of sLeX including the contributions from more than 15 international research groups will be described, followed by a brief view of the sLeX detection focusing on monosaccharides and linkages. This review is valuable for those readers who are interested in the chemistry and biology of sLeX.

Despite recent advancements in the field of neuro-ophthalmology, the rising rates of neurological and ophthalmological conditions, mismatches between supply and demand of clinicians, and an aging population underscore the urgent need to explore new therapeutic approaches within the field. Glucagon-like peptide 1 receptor agonists (GLP-1RAs), traditionally used in the treatment of type 2 diabetes, are becoming increasingly appreciated for their diverse applications. Recently, GLP-1RAs have been approved for the treatment of obesity and recognized for their cardioprotective effects. Emerging evidence indicates some GLP-1RAs can cross the blood-brain barrier and may have neuroprotective effects. Therefore, this article aims to review the literature on the neurologic and neuro-ophthalmic role of glucagon-like peptide 1 (GLP-1). This article describes GLP-1 peptide characteristics and the mechanisms mediating its known role in increasing insulin, decreasing glucagon, delaying gastric emptying, and promoting satiety. This article identifies the sources and targets of GLP-1 in the brain and review the mechanisms which mediate its neuroprotective effects, as well as implications for Alzheimer’s disease (AD) and Parkinson’s disease (PD). Furthermore, the preclinical works which unravel the effects of GLP-1 in ocular dynamics and the preclinical literature regarding GLP-1RA use in the management of several neuro-ophthalmic conditions, including diabetic retinopathy (DR), glaucoma, and idiopathic intracranial hypertension (IIH) are discussed.

Bacterial infections constitute one of the major cases of primary medical incidences worldwide. Historically, the fight against bacterial infections in humans has been an ongoing battle, due to the ability of bacteria to adapt and to survive. Indeed, bacteria have developed various mechanisms of resistance against several therapeutic agents. Consequently, the scientific community is always interested in search of new therapeutic agents, which are able to efficiently kill resistant-bacterial strains. This article covers the most recent antibacterial molecules approved by the Food and Drugs Administration (FDA) and European Medicines Agency (EMA) from 2012 to 2022 and intends to focus on synthetic derivatives to give a pedagogical view, with the goal of highlighting the importance of organic synthesis to obtain greater efficacy. A focus will be made on studies describing the structure and activity of the organic molecules and their interactions with their respective biological targets.

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in December 2019 quickly escalated to pandemic levels and had a severe impact on public health. There are 761 million confirmed coronavirus disease 2019 (COVID-19) cases, with over 6.88 million deaths worldwide till March 2023. Severe cases of the disease caused critical respiratory failure followed by multiorgan involvement. Clinical escalation of COVID-19 has been correlated with markedly increased plasma inflammatory markers [e.g., C-reactive protein (CRP)] and pro-inflammatory cytokine levels [e.g., interleukin (IL)-6, tumor necrosis factor-α (TNF-α)]. Therapeutic options have mostly utilized corticosteroids, antivirals (e.g., remdesivir), and monoclonal antibody-based immunomodulation (e.g., tocilizumab). These existing treatments have adverse side effects, inadequate efficacy, and limitations in administering to patients with comorbidities and other underlying diseases. Monoclonal antibody-based therapies and some of the antivirals are very costly. Many phytochemicals have previously reported anti-inflammatory, antiviral, and antioxidant properties. Studying the effectiveness of such phytochemicals against COVID-19 and identifying new plant-derived molecules with antiviral properties have been a focus since the SARS-CoV-2 outbreak. This review article has documented in vitro, in vivo, and clinical studies encompassing 28 different phytochemicals belonging to various chemical groups (e.g., polyphenols, alkaloids, terpenes) that show anti-COVID-19 activity. These findings suggest that multiple phytochemicals can interfere with virus entry and replication inside the host cell. Many of them can protect from cytokine storm by acting on intracellular signalling pathways in addition to inhibiting virus multiplication. Phytochemicals may prove useful in alleviating post-COVID complications associated with kidney injury, and central nervous system complications, as well. Plant-derived compounds are usually cheaper and have fewer side effects. But, developing new formulations with better absorption and bioavailability remains a priority. This review informs the readers of the current status and indicates the ongoing research in this highly relevant field.

Seaweeds, also known as marine algae, have gained attention as a promising source of bioactive compounds with potential applications in drug discovery. This review explores the emerging field of seaweed-based drug discovery and highlights the diverse range of bioactive compounds found in seaweeds, including polysaccharides, phlorotannins, pigments, and peptides. These compounds exhibit various pharmacological activities such as antioxidant, anti-inflammatory, antimicrobial, antiviral, and anticancer effects. Seaweeds have demonstrated particular promise in the areas of cancer research, with certain species showing potent antitumor properties. Additionally, their anti-inflammatory, antimicrobial, and neuroprotective potential has captured scientific interest in the treatment of chronic diseases and neurodegenerative disorders. However, challenges related to compound identification, extraction methods, scalability of seaweed cultivation, and understanding the mechanisms of action still need to be addressed. As researchers employ advanced technologies and dive deeper into the chemical composition of seaweeds, the untapped potential of these marine organisms in drug discovery awaits further exploration and holds significant promise for future therapeutic advancements.

Protein therapeutics are extensively used in the treatment of autoimmune diseases, but a subset of patients appears to be refractory to these treatments, mainly due to the development of an immune response to the drug. A better understanding of the mechanism underlying the therapeutic drug’s failure becomes fundamental for the development of new and more effective treatments. Unfortunately, there are few cases where the exact mechanisms through which drugs bypass immunological tolerance and provoke immunogenicity have been studied. In this context, peptide epitope identification gained increasing importance in investigating the molecular mechanism of therapeutic drug’s immune responses. Despite peptide identification and use to monitor anti-drug antibody (ADA) profiles is a promising research field, their use is far away from a wide application both at the research and at the commercial level. Herein it is reported a compilation of studies in which peptides are directly involved in anti-drug immune responses, becoming the molecular key step for a better understanding of refractory reactions in therapeutic drugs. An overview on T-cell and B-cell peptide recognition is given, showing the growing potential and advantages of peptides when used in the field of refractoriness to drugs. This review includes studies describing antigenic peptides that enable enhanced ADA detection directly in patients’ sera, as well as the proof of concept that asses the use of peptides instead of proteins, to facilitate the identification of neutralizing ADA.