Nanoparticles (NPs) have become key tools in modern drug delivery, especially when used alongside natural compounds. This combination can improve how drugs are absorbed and directed to specific targets in the body. Benefits include higher drug loading, controlled and sustained release, longer presence in the bloodstream, and reduced side effects. These advantages contribute to safer and more efficient therapies.

Among the various nanoparticle types, gold nanoparticles (AuNPs) stand out due to their easy production, strong stability, and unique physical and chemical traits. These properties make them excellent carriers for both drugs and genetic material, especially in cancer-related applications.

One group of natural compounds with promising anticancer activity is the abietane diterpenoids, such as 7α-acetoxy-6β-hydroxyroyleanone (Roy), found in Plectranthus species. Despite their potential, their clinical use is limited by poor water solubility and low bioavailability. To overcome these issues, Roy and one Roy-esterified derivative were incorporated into gold nanoparticle-based systems.

These nanoformulations were evaluated for characteristics like particle size (29.37 nm), polydispersity index (PDI, 0.399), surface charge (zeta potential, −6.84), and drug encapsulation efficiency (79.4%). In vitro experiments using breast cancer cell lines (MDA-MB-231, 4T1, and MCF7) showed that Roy-loaded AuNPs had significantly stronger anticancer effects than Roy alone or unmodified AuNPs. Notably, these systems also demonstrated selectivity, affecting cancer cells while sparing healthy human dermal fibroblasts (HDFs), suggesting strong potential for targeted cancer therapy. These results represent meaningful progress in the development of innovative drug delivery systems for cancer therapy.