Development and stability evaluation of a low-complexity topical O/W emulsion containing CBD- and CBG-rich extracts

Abstract Currently, cannabinoid-based products approved for topical use are still limited, although there is a potential of cannabinoids use in dermatological conditions. This study aimed to develop a low-complexity oil-in-water (O/W) emulsion containing CBD- and CBG-rich extracts, characterize the antioxidant, antimicrobial activities of the extracts, and evaluate stability of the resulting formulations. Both extracts showed relevant antioxidant activity, with DPPH radical scavenging values of 38.3% ± 2.82 for CBD and 31.7% ± 1.26 for CBG at 0.5 mg/mL, and FRAP values of 25 ± 0.9 and 50 ± 1.1 mg GAE/g extract, respectively. Higher phenolic and flavonoid contents were observed for CBG, which was consistent with its superior antioxidant performance in the FRAP assay. Regarding antimicrobial activity, the results were identical for both extracts, being more promising against Gram-positive strains, as they inhibited the microbial growth with concentration between 1.0 and 2.0 µg/mL of extract. The developed emulsions maintained homogeneous appearance, pH and high consistency over six months under accelerated conditions. However, a significant reduction in cannabinoid content was observed, particularly for CBD, which showed a 65% decrease compared to 16% for CBG, indicating limited chemical stability under the evaluated conditions. These findings support the feasibility of preparing low-complexity cannabinoid-containing emulsions, although their rheological performance, cannabinoid release, and chemical stability require further investigation. The greater stability of CBG suggests its potential as a more robust candidate for formulations.