Evaluation of the antioxidant efficacy of extracts/ ingredients used in skin care products

The so-called active ingredients in skin care product formulations are purported to deliver the intended functions of the product. Active ingredients, such as the antioxidants can efficiently protect the skin if the activities are retained after incorporating into the base matrices in the product formulation. Here, we investigated the antioxidant activities of 24 extracts/compounds that are being used in skin care formulations and their ability to retain the activities (efficacy) after being mixed with the base matrices. The antioxidant activities were evaluated using 2, 2’-azino-bis (3- ethylbenzothiazoline-6-sulphonic acid (ABTS) and diphenyl-picryl hydrazine (DPPH) assays. To test the efficacy of the samples in formulation, the samples were mixed with base cream 1%, 2% and 4% (w:w) and allowed to settle overnight. Results were expressed as either percentage inhibition (%) or IC50 (μg/mL). Out of the 24 samples, ten exhibited significantly high antioxidant activities with resveratrol> pomegranate> green tea> mango> amla> bearberry> ellagic acid> tetrahydrocurcuminoid> Rhodiola rosea> kakadu plum in the ABTS assay. In the DPPH assay, green tea> pomegranate> tetrahydrocurcuminoid> mango> amla> resveratrol> bearberry> Rhodiola rosea>kakudu plum>ellagic acid. Four out of the ten samples (amla, green tea, mango and pomegranate extracts) had IC50 value lower than Trolox standard and were included in the efficacy test. Trolox standard and amla extract seemed to retain their antioxidant activities in the formulations, while green tea and pomegranate extracts had a decrease in activities. Only mango extract had a synergistic effect with the cream base with higher antioxidant activity observed compared with the extract alone. This study demonstrates the potential interaction between active and vehicle compounds, which may hinder or enhance the activities of the active ingredients in the final product. The outcome of the research has an impact in the cosmetic product formulation particularly in the quality control, chemistry and efficacy of the finished products.