Formulation and In-Vitro In-Vivo Evaluation of Creams Containing Plants Extracts having Skin Soothing and Depigmenting effect

Abstract

Plant extracts due to their antioxidant properties and lack of any toxicity or side effects to the human skin are becoming prevalent as ingredients in different cosmeceutical preparations because they can protect the skin from harmful ultraviolet radiations and the free radicals produced due to these radiations. Plant extracts are useful in treating different skin conditions and are effective for depigmenting and soothing effects as well as act as moisturizers when applied topically due to the different agents they contain. The current work aimed to prepare stable formulations that act as vehicle for the effective and safe delivery of active ingredients in the form of topical water-in-oil (W/O) emulsion; with comparable antioxidant properties, their in-vitro characterization and in-vivo study on human volunteers. Stable placebo formulation (F4) without active (plant extract) and stable formulations F1 (Hibiscus rosa-sinensis extract), F2 (Bombax ceiba extract) and F3 (Matricaria recutita extract) containing plant extracts were developed as creams of water-in-oil type. Antioxidant activities of plant extracts were determined by three different methods namely DPPH, reducing power activity (RPA) and nitric oxide (NO) scavenging activity while those of formulations containing plant extract were determined by DPPH (2, 2-di-phenyl-1-picrylhydrazyl) assay. Phenolic and flavonoid contents were also assessed in the extracts. In-vitro characterization was done to investigate the changes in the physical stability (color, liquefaction, phase separation, centrifugation, viscosity and rheological parameters) in active formulations (F1, F2 and F3) containing plant extract and placebo (F4) by storing them at different storage conditions, i.e. 8 ºC, 25 ºC, 40 ºC and 40 ºC + 75% RH for a span of 12 weeks. In-vivo characterization was done to measure the effects of active formulations (F1, F2 and F3) on various skin parameters like melanin, erythema, moisture contents, elasticity, sebum and surface evaluation of living skin (SELS parameters) on human volunteers by taking the reading at specific time intervals for a total of three months. For this purpose a single blinded, split face study was conducted by dividing the volunteers into three groups with 11 volunteers in each group. Statistical tools of two-way ANOVA and paired sample t-test were employed to assess the effects produced. Antioxidant activities of Hibiscus rosa-sinensis, Bombax ceiba and Matricaria recutita extracts were 78%, 90% and 87%, respectively by DPPH method. The fresh active formulations (F1, F2 and F3) containing these extracts showed 72%, 80% and 81% anti-oxidant activities, respectively while placebo formulation (F4) showed no activity. Active formulations containing plant extracts (4% each) as well as placebo F4 showed good stability and rheological characteristics for a total period of 12 weeks. Phytochemical analysis revealed that extracts are rich in phenolic and flavonoid contents. Active formulations F1, F2 and F3 exhibited significant changes in different skin parameters while placebo (F4) displayed an insignificant change in skin melanin (P=0.05), elasticity (P=0.05), and moisture contents (P=0.000) while an increase in sebum was observed. Active formulations depicted statistically significant (P=0.05) effects on surface evaluation of living skin parameters i.e., skin roughness (SEr), skin scaliness (SEsc), skin smoothness (SEsm) and skin wrinkles (SEw) while placebo formulation did not appear to affect SELS parameters significantly. On the basis of these findings, it is concluded that the formulations containing plant extracts were found safe and effective for the improvement of skin parameters. Keywords: plant extracts, W/O emulsion, rheology, stability, viscosity, melanin, erythema.