: Cysteine is one of the major intermediate products of cellular amino-acid metabolism. It is a semi-essential amino acid for protein synthesis. Besides, it is also employed in the regulation of major endogenous anti-oxidant molecules i.e., reduced glutathione (GSH). Further, it is a precursor of multiple sulfur-containing molecules like hydrogen sulfide, lanthionine, taurine, coenzyme A and biotin. It is also one of the key molecules for post-translational modifications of various cellular proteins. In physiological conditions, it is employed in the sulfhydration process and plays a key role in the physiology modification of the inflammatory process in various organs, including the neurological system. The catabolism of cysteine is regulated by cysteine dioxygenase enzyme activity. The dysregulated conditions of cysteine and cysteine-associated hydrogen sulfide metabolism are widely employed in the acceleration of the neurodegenerative process. Moreover, the upregulation of cysteine and hydrogen sulfide synthesis occurs via the reverse trans-sulfuration process. This process helps to manage the worsening of a pathological condition of a cellular system. Moreover, it is also employed in the accumulation of homocysteine contents. Further, both cysteine and homocysteine molecules are widely accepted as biomarkers for various types of diseases. Therefore, the targets involved in the regulation of cysteine have been considered as valid targets to treat various disorders like cardiac disease, ischemic stroke, diabetes, cancer, and renal dysfunction.

Diabetic retinopathy (DR) primarily progresses into retinal degeneration caused by microvascular dysfunction. The pathophysiology of DR progression is still uncertain. This study investigates the function of beta-carotene (PBC) originating from palm oil mill effluent in the treatment of diabetes in mice. An intraperitoneal injection of streptozotocin (35 mg/kg) was used to induce diabetes, which was then accelerated by an intravitreal (i.vit.) injection of STZ (20 µL on day 7). PBC (50 and 100 mg/kg) and dexamethasone (DEX: 10 mg/kg) were also administered orally (p.o.) for 21 days. At various time intervals, the optomotor response (OMR) and visual-cue function test (VCFT) responses were evaluated. Biomarkers, such as reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARSs), and catalase activity were determined in retinal tissue samples. DR significantly lowers the spatial frequency threshold (SFT) and time spent in the target quadrant (TSTQ), increases the reaching time in the visual-cue platform (RVCP), lowers retinal GSH and catalase activity levels, and elevates TBARS levels. The treatments of PBC and DEX also ameliorate STZ-induced DR alterations. The potential ameliorative activity of PBC in DR is attributed to its anti-diabetic, anti-oxidative, and control of blood–retinal barrier layer properties.

Retinopathy is one of the most common complications of diabetes mellitus. Diabetic retinopathy (DR) occurs due to microvascular damage in retinal tissues provoked by high blood sugar levels. The available drugs for DR are limited. Astaxanthin (AST) has anti-hypertensive, anti-obesity, and anti-diabetic properties. However, the therapeutic effect of AST on DR remains elusive. The present study is designed to investigate the effects of AST on DR via inhibition of neuron-specific enolase (NSE) activity. DR was induced by the administration of streptozotocin (STZ, 35 mg/kg: intraperitoneal; and 20 μL of STZ: intravitreal) in mice. AST (10 and 20 mg/kg) was administered orally (p.o.) for 21 days. The DR associated visual changes were assessed at different time intervals via optokinetic motor response (OMR) and penta-maze (PM) tests. Blood glucose level as well as retinal catalase, lactate dehydrogenase (LDH), & neuron-specific enolase (NSE) were estimated. The reference drug i.e., dexamethasone (DEX, 10 mg/kg; p.o.) was administered for 21 days. The administration of AST showed significant ameliorative potential in DR. Hence, AST can be used as a natural medicine for the management of DR due to its potential antioxidant, anti-diabetic, and NSE inhibitory properties.

COVID-19 is a respiratory infection caused by a newer strain of coronavirus known as SARS-CoV-2. The major problem of COVID-19 infections is the ARDS followed by respiratory failure, organ failure, and even death with multiple organ dysfunction including cardiovascular collapse. Moreover, it affects the old age population linked with co-morbid conditions. The deficiency of diet, micronutrients, and vitamins also plays a key role in diminishing the immune power and higher rate of viral infectivity. The possible reasons and management methods are discussed in this review. The management methods enhance the host immune system via multi-functional and multi-targeted actions. The global rate of COVID-19 outbreak makes the greater attention towards the development of newer medicines. The drug discovery process is based on the exposure of viral proteins, genome sequence, replication mechanisms, pathophysiological mechanisms, and host cell components (as a target) reactions. This article highlights the overview of coronavirus components, the replications process, and possible targets for the management of coronavirus infections. It may lead to the rapid development of newer medicines for the treatment of coronavirus infections.