Allamanda cathartica (Linn.) leaf extract-encapsulated phytoemulsions: formulation, characterization and in vitro–in vivo biological evaluations

Abstract

Allamanda cathartica Linn. (A. cathartica L.). belongs to the Apocynaceae family and is reported to have various pharmacological activities. The present study aims to extract and formulate A. cathartica leaf extract-based emulsions, termed phytoemulsions, for improved therapeutic efficacy. Based on the results of solubility and FTIR studies, OA, T80 and P400 were selected as the oil, surfactant, and co-surfactant/stabilizer. Four different phytoemulsions (F1–F4) were formulated based on extracts obtained from different extraction solvents, F1 (organic methanolic), F2 (aqueous), F3 (ethyl acetate), and F4 (hydroalcoholic). In vitro antioxidant (DPPH and ABTS) assay results showed that all phytoemulsions exhibited potential antioxidant activity, with F3 showing the highest activity. In vitro antibacterial (zone of inhibition) assay results showed that F2 and F3 exhibited antibacterial effects against Streptococcus pyogenes (6.3 ± 0.58 mm) and Klebsiella pneumoniae (7.68 ± 0.58 mm), respectively. In vitro MTT assay findings demonstrated that all the phytoemulsions exhibited potential chemotherapeutic effects against both A431 (human epidermoid cancer) and MCF-7 (breast cancer) cells in a dose-dependent manner (24 h), with F3 showing the highest effect. Also, F3-treated cells exhibited the highest intracellular ROS and nitric oxide release. In vivo skin irritation studies revealed that phytoemulsion-treated Wistar rats showed no signs of inflammation, redness, and ablation with a primary irritation index of zero, confirming that the phytoemulsions were safe for topical application. In conclusion, A. cathartica leaf extract-based phytoemulsions showed potential antioxidant, anticancer (A431 and MCF-7) and antibacterial (F3 and F2 only) effects with high biodegradability and stability.