Resolving the Chemistry and Bioactivity of Juglone: From Natural Extracts to Applications

Juglone (5-hydroxynaphthoquinone) is a naturally occurring naphthoquinone broadly present in Juglans species and selected taxa of other plant families. Owing to its redox-active structure, it exhibits a wide range of biological effects, including antimicrobial, anti-inflammatory, and cytotoxic activity. Despite increasing interest in its potential applications, research on juglone remains dispersed, particularly with regard to extraction strategies, analytical approaches, and the relationship between composition and biological activity. This review provides an integrated overview of juglone, focusing on its natural occurrence, modern extraction techniques, analytical determination, and reported biological properties. Special attention is given to emerging green extraction approaches and challenges related to process standardization and reproducibility. The paper also highlights current limitations in linking phytochemical composition with biological effects and outlines future directions for improving the reliability and applicability of juglone-based systems. By combining chemical, analytical, and application-oriented perspectives, this paper offers a concise framework for further research and supports the development of safe, efficient, and sustainable strategies for the utilization of juglone in various industrial sectors.