The study investigated the changes in the metabolite, antioxidant and α-glucosidase inhibitory activities of Phyllanthus niruri after three drying treatments: air, freeze and oven dryings. Water extracts and extracts obtained using different solvent ratios of ethanol and methanol (50, 70, 80 and 100%) were compared. The relationships among the antioxidant, α-glucosidase inhibitory activity and metabolite levels of the extracts were evaluated using partial least-square analysis (PLS). The solvent selectivity was assessed based on the phytochemical constituents present in the extract and their concentrations quantitatively analyzed using high performance liquid chromatography. The freeze-dried P. niruri samples that were extracted with the mixture of ethanol or methanol with low ratio of water showed higher biological activity values compared with the other extracts. The PLS results for the ethanolic with different ratio and water extracts demonstrated that phenolic acids (chlorogenic acid and ellagic acid) and flavonoids were highly linked to strong α-glucosidase inhibitory and antioxidant activities.
In order to investigate the role of roasting conditions in antioxidant formation, methanol and hot water extracts from Robusta coffee beans roasted for various lengths of time and at various temperatures were analyzed for total phenolic acid, chlorogenic acid, and caffeine content, as well as for their antioxidant activities using 1,1-diphenyl-2-picryhydrazyl (DPPH), thiobarbituric acid (TBA), and malonaldehyde/gas chromatography (MA/GC) assays. The amount of total phenolics in methanol extracts decreased linearly over the roasting temperature from 63.51 ± 0.77 mg chlorogenic acid equivalent (CAE)/g coffee beans (roasted at 200°C) to 42.56 ± 0.33 mg CAE/g coffee beans (roasted at 240°C). The total chlorogenic acid content decreased when the roasting time was increased from 78.33 ± 1.41 mg/g (green coffee beans) to 4.31 ± 0.23 mg/g (roasted for 16 min at 250°C). All methanol extracts from roasted coffee beans possessed over 90% antioxidant activities in the DPPH assay. The antioxidant activity of methanol extracts ranged from 41.38 ± 1.77% (roasted at 250°C for 10 min) to 98.20 ± 1.49% (roasted at 230°C for 16 min) as tested by the TBA assay. The antioxidant activity of methanol extracts of green coffee beans and roasted coffee beans ranged from 93.01% (green coffee beans) to 98.62 ± 1.32% (roasted at 250°C for 14 min) in the MA/GC assays. All hot water extracts exhibited moderate pro-oxidant activities in TBA and MA/GC assays. The results indicated that roasting conditions of coffee beans play an important role in the formation of antioxidants in brewed coffee, which can be dietary supplements having beneficial effect to human health.
The impact of tropical seasons (dry and wet) and growth stages (8, 10 and 12 weeks) of Cosmos caudatus on the antioxidant activity (AA), total phenolic content (TPC) as well as the level of bioactive compounds were evaluated using high performance liquid chromatography (HPLC). The plant morphology (plant height) also showed variation between the two seasons. Samples planted from June to August (during the dry season) exhibited a remarkably higher bioactivity and height than those planted from October to December (during the wet season). The samples that were harvested at eight weeks of age during the dry season showed the highest bioactivity with values of 26.04 g GAE/100 g and 22.1 μg/ml for TPC and IC₅₀, respectively. Identification of phytochemical constituents in the C. caudatus extract was carried out by liquid chromatography coupled with diode array detection and electrospray tandem mass (LC-DAD-ESIMS/MS) technique and the confirmation of constituents was achieved by comparison with literature data and/or co-chromatography with authentic standards. Six compounds were indentified including quercetin 3-O-rhamnoside, quercetin 3-O-glucoside, rutin, quercetin 3-O-arabinofuranoside, quercetin 3-O-galactoside and chlorogenic acid. Their concentrations showed significant variance among the 8, 10 and 12-week-old herbs during both seasons.