Structural characterization of phenolic compounds and antioxidant activity of the phenolic-rich fraction from defatted adlay ( Coix lachryma-jobi L . var. ma-yuen Stapf) seed meal

Melanogenesis inhibitors from Coix lacryma-jobi seeds in B16-F10 melanoma cells

An adenine derivative, 9-β-D-glucopyranosyl adenine, reported for the first time from a natural source, in addition to nine known compounds were isolated from the seeds of Coix lacryma-jobi. Their structures were elucidated based on extensive spectroscopic and chemical studies. The isolated compounds and the ethanol extract have been assayed for melanin inhibition using B16-F10 melanoma cell line. The results of our study suggested the potential use of Coix lacryma-jobi seeds as a skin whitening agent and reveal the seeds to be a rich source of important phytochemicals with melanogenesis inhibitory activity. Among the isolated compounds, coixol (2) and 2-O-β-glucopyranosyl-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (8) exhibited potent melanogenesis inhibitory activity with no obvious melanocytotoxicity. The rest of the compounds showed weak to moderate activity.

Optimization of Extraction Conditions for Maximal Phenolic, Flavonoid and Antioxidant Activity from Melaleuca bracteata Leaves Using the Response Surface Methodology

Melaleuca bracteata is a yellow-leaved tree belonging to the Melaleuca genus. Species from this genus are known to be good sources of natural antioxidants, for example, the “tea tree oil” derived from M. alternifolia is used in food processing to extend the shelf life of products. In order to determine whether M. bracteata contains novel natural antioxidants, the components of M. bracteata ethanol extracts were analyzed by gas chromatography–mass spectrometry. Total phenolic and flavonoid contents were extracted and the antioxidant activities of the extracts evaluated. Single-factor experiments, central composite rotatable design (CCRD) and response surface methodology (RSM) were used to optimize the extraction conditions for total phenolic content (TPC) and total flavonoid content (TFC). Ferric reducing power (FRP) and 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH·) scavenging capacity were used as the evaluation indices of antioxidant activity. The results showed that the main components of M. bracteata ethanol extracts are methyl eugenol (86.86%) and trans-cinnamic acid methyl ester (6.41%). The single-factor experiments revealed that the ethanol concentration is the key factor determining the TPC, TFC, FRP and DPPH·scavenging capacity. RSM results indicated that the optimal condition of all four evaluation indices was achieved by extracting for 3.65 days at 53.26°C in 34.81% ethanol. Under these conditions, the TPC, TFC, FRP and DPPH·scavenging capacity reached values of 88.6 ± 1.3 mg GAE/g DW, 19.4 ± 0.2 mg RE/g DW, 2.37 ± 0.01 mM Fe²⁺/g DW and 86.0 ± 0.3%, respectively, which were higher than those of the positive control, methyl eugenol (FRP 0.97 ± 0.02 mM, DPPH·scavenging capacity 58.6 ± 0.7%) at comparable concentrations. Therefore, the extracts of M. bracteata leaves have higher antioxidant activity, which did not only attributed to the methyl eugenol. Further research could lead to the development of a potent new natural antioxidant.

Evaluation of the antibacterial and antioxidant activities of chitosan edible films incorporated with organic essential oils obtained from four Thymus species

The aims of this study were to evaluate, (1) the antibacterial properties, (2) the total phenol content and (3) the antioxidant activity, of chitosan edible films incorporated with certified organic essential oils (EOs) obtained from Thymus zygis, Thymus mastichina, Thymus capitatus and Thymus vulgaris. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films while for the antioxidant activity, two different analytical assays were used (DPPH and FRAP). As regard antibacterial activity, films containing only chitosan were not effective against any of tested bacteria. Chitosan films containing T. capitatus EO (CH + TCEO) was more effective against Listeria innocua and Alcaligenes faecalis whilst chitosan films containing T. mastichina EO (CH + TMEO) had the highest inhibition halos against Serratia marcescens. For and Enterobacter amnigenus no antibacterial activity was achieved. Chitosan films added with Thymus essential oils showed antioxidant activity, at all concentrations and with all methods assayed. CH + TZEO had the highest antioxidant activity revealed with DPPH assay. However in CH + TCEO showed best antioxidant effect when assessed with FRAP assay. The results showed that chitosan edible films incorporated with organic Thymus EOs could be used as active films in food industry due to its antibacterial and antioxidant activities.