Polyherbal phytosomal gel for enhanced topical delivery: design, optimization by central composite design, in vitro and ex-vivo evaluation

Annona squamosa (AS) and Cinnamomum tamala (CT) leaves have been used traditionally and have well reported various pharmacological activities which justify their topical use. But the majority of compounds present are phenolic compounds which due to their polar nature are unable to permeate through the skin. Therefore, polyherbal phytosomes of ethanolic extracts of AS and CT were combined in a ratio of 1:1 to get polyherbal Ethanolic extract (PHEE) and polyherbal phytosomes (PHP) were prepared and optimized using Response Surface methodology by applying Central Composite design (CCD) for studying the effect of drug soya lecithin ratio and speed of rotation on responses like vesicle size and entrapment efficiency. Followed by numerical optimization, PHP with vesicle size of 215.5 ± 0.45 nm and Entrapment efficiency of 85.24 ± 0.05% were obtained. These PHP were characterized with FTIR, DSC, SEM and XRD. The PHP showed % cumulative drug release of 84.22 ± 5.62%. For easy application on the skin these phytosomes were incorporated in Carbopol 934 gel matrix and evaluated for physical appearance, pH, viscosity and drug content. The ex vivo permeation of the phytosomal gel (PG) was compared with a conventional gel containing PHEE. A significant improvement in permeation was observed in case of PG with 36.62 ± 3.33 µg/cm2 of drug permeated in 24 hours whereas 17.06 ± 1.54 µg/cm2 through the conventional gel. The PHP and PG were found stable during stability studies for six months. Polyherbal phytosomal gel can be a good carrier for herbal extracts for topical delivery.