Natural products with aggregation-induced emission properties: from discovery to their multifunctional applications

Aggregation-induced emission (AIE) materials derived from natural products have the advantages of non-synthetic, good biocompatibility, natural degradation and pharmacological activity, and are gradually becoming a powerful tool in environmental monitoring, biological imaging and disease diagnosis. Here, we review AIE materials discovered from natural products, including alkaloids such as berberine, flavonoid polyphenols such as quercetin, non-flavonoid polyphenols such as tannic acid, and other natural compounds such as saponins and vitamins. AIE mechanisms of these materials include restriction of intramolecular/intermolecular motion (RIM), torsional intramolecular charge transfer (TICT), excited state intramolecular proton transfer (ESIPT), J-aggregate and clusterization-triggered emission (CTE). Based on remarkable AIE properties, these natural products show great potential in the fields of pH, ion and biomarker sensing, cell imaging and biological diagnosis and treatment. This paper is expected to deepen the understanding of aggregation-induced luminescence, inspire the exploration of AIE molecules from natural products and develop new applications.