Photochemical and photophysical behavior of molecules in supramolecular assemblies are different and more selective than in gas and isotropic solution phases.

Natural Product Synthesis (NPS) is a cornerstone of organic chemistry, historically rooted in the dual goals of structure elucidation and synthetic strategy development for bioactive compounds. Initially focused on identifying the structures of medicinally relevant natural products, NPS has evolved into a dynamic field with applications in drug discovery, immunotherapy, and smart materials. This evolution has been propelled by advances in reaction design, mechanistic insight, and the integration of green chemistry principles. A particularly promising development in NPS is the use of photochemistry, which harnesses light—a renewable energy source—to drive chemical transformations. Photochemical reactions offer unique excited-state reactivity, enabling synthetic pathways that are often inaccessible through thermal methods. Their precision and sustainability make them ideal for modern synthetic challenges. This review explores a wide range of photochemical reactions, from classical to contemporary, emphasizing their role in total synthesis. By showcasing their potential, the review aims to encourage broader adoption of photochemical strategies in the synthesis of complex natural products, promoting innovation at the intersection of molecular complexity, sustainability, and synthetic efficiency.

The world has recently witnessed the dire consequences of microbial infections in the form of the spread of COVID 19. Like viruses, bacterial infections too are a serious global health concern, especially because of the evolution of multidrug-resistant (MDR) bacterial populations. MDR bacteria are a result of the mindless use and misuse of antibiotics all over the world. Hence, there arises a need to find alternative strategies to effectively combat bacterial infections; all the more so for MDR bacterial infections. A lot of research has been conducted to find alternative antibacterial strategies such as phage therapy, the synthesis of antimicrobial peptides, the development of CRISPR-Cas systems, the incorporation of pro- and pre-biotics into our food or as supplements, and the development of bactericidal nanotechnology and antibacterial materials. Of these many strategies, this review focusses on the last one—the development of antibacterial materials. This article explores the potential of plant-derived natural colorants to serve as effective antibiotic materials to be used in various industries ranging from food, textile, paper, and leather to the pharmaceutical industry. Some major advantages of developing plant-derived natural colorants into antibacterial materials is that many of them possess inherent medicinal properties, they are biocompatible, non-toxic for humans, and biodegradable, and hence environment friendly. Many plant-derived natural colorants, like curcumin, indigo, lawsone, emodin, etc., have already been well studied for their antimicrobial properties. This review article aims at integrating some relevant studies to offer a cohesive overview of the current state of knowledge on the antibacterial properties of plant-derived natural colorants.

Cholesta-5,7,9(11)-trien-3β-ol (9,11-dehydroprovitamin D₃, CTL) is used as a fluorescent probe to track the presence and migration of cholesterol in vivo. We recently described the photochemistry and photophysics of CTL in degassed and air-saturated tetrahydrofuran (THF) solution, an aprotic solvent. The zwitterionic nature of the singlet excited state, ¹CTL* is revealed in ethanol, a protic solvent. In ethanol, the products observed in THF are accompanied by ether photoadducts and by photoreduction of the triene moiety to four dienes, including provitamin D₃. The major diene retains the conjugated s-trans-diene chromophore and the minor is unconjugated, involving 1,4-addition of H at the 7 and 11 positions. In the presence of air, peroxide formation is a major reaction channel as in THF. X-ray crystallography confirmed the identification of two of the new diene products as well as of a peroxide rearrangement product.