The effect of drying and storage on the quality of cosmeceutical species Leucosidea Sericea and Greyia Flanaganii

Abstract

The use of plants for cosmeceutical applications is becoming more important since “safer” and more “natural” skin products are gaining popularity. The effect of different drying methods and storage conditions on metabolite changes and biological activity of two species with cosmeceutical application namely Greyia flanaganii and Leucosidea sericea were investigated using 1H-NMR metabolomics. The multivariate analysis (PCA and OPLS-DA), and 1H-NMR sample spectra were used to analyse the significant differences (P<0.05) resulting from the different treatments. The effect of these treatments on anti-tyrosinase and anti-bacterial (against Staphylococcus aureus) activity of G.flanaganii and L.sericea ethanol leaf extracts respectively, was further investigated to assess the quality. Four different drying methods adopted were freeze drying, oven drying at 50°C, air drying at room temperature and sun drying in a greenhouse. The dried leaf extracts were stored in three different conditions of fridge, freezer and shade conditions and samples from each storage condition taken for analysis at three and six months of storage. The chemical constituents of the leaf extracts of both species were not affected by the drying method and the storage condition, but the concentrations of the metabolites changed. The treatments did not show a significant difference (P<0.05) on the biological activity of the extracts. However, G.flanaganii plant material harvested from the University of Pretoria exhibited a higher anti-tyrosinase activity than material harvested from Mothong heritage site. In G. flanaganii freshly freeze and oven dried extracts exhibited a higher anti-tyrosinase activity with fifty percent inhibitory (IC50) activity of 16.8±0.69 μg/ml and 15.73±0.85 μg/ml respectively than the activity of sun and air dried with IC50 values of 33.08±0.78 μg/ml and 36.86±2.01 μg/ml respectively. The metabolite concentrations and anti-tyrosinase activity dropped significantly after storage. Leucosidea sericea oven and freeze dried extracts, exhibited good anti-bacterial activity with a minimum inhibitory concentration (MIC) value of 0.25 μg/ml and 0.125 μg/ml respectively as compared to sun and air dried extracts with the same MIC value of 0.5 μg/ml. Freeze dried samples showed the best anti-bacterial activity (MIC 0.125 μg/ml) compared to other drying methods. Fridge and freezer storage conditions enhanced the activity of stored sample.