*Review* **Functional Studies of Plant Latex as a Rich Source of Bioactive Compounds: Focus on Proteins and Alkaloids**

**Joanna Gracz-Bernaciak , Oliwia Mazur and Robert Nawrot \***

Molecular Virology Research Unit, Institute of Experimental Biology, Faculty of Biology, Adam Mickiewicz University, Pozna ´n, Uniwersytetu Pozna ´nskiego 6, 61-614 Pozna ´n, Poland; joanna.gracz-bernaciak@amu.edu.pl (J.G.-B.); oliwia.mazur@amu.edu.pl (O.M.) **\*** Correspondence: rnawrot@amu.edu.pl; Tel.: +48-61-829-5931

**Abstract:** Latex, a sticky emulsion produced by specialized cells called laticifers, is a crucial part of a plant's defense system against herbivory and pathogens. It consists of a broad spectrum of active compounds, which are beneficial not only for plants, but for human health as well, enough to mention the use of morphine or codeine from poppy latex. Here, we reviewed latex's general role in plant physiology and the significance of particular compounds (alkaloids and proteins) to its defense system with the example of *Chelidonium majus* L. from the poppy family. We further attempt to present latex chemicals used so far in medicine and then focus on functional studies of proteins and other compounds with potential pharmacological activities using modern techniques such as CRISPR/Cas9 gene editing. Despite the centuries-old tradition of using latex-bearing plants in therapies, there are still a lot of promising molecules waiting to be explored.

**Keywords:** latex; antiviral proteins; antimicrobial compounds; cytotoxicity; drug discovery; *Chelidonium majus*; CRISPR/Cas9
