Antioxidant capacity of different African seeds and vegetables and correlation with the contents of ascorbic acid, phenolics and flavonoids

In vitro antidiabetic activity of Treculia africana leaf extracts: identification of chlorogenic acid and α-mangostin

OBJECTIVE

This research studied two extracts from Treculia africana leaves for their potential against hyperglycaemia-related disorders.

METHODS

The influence of the extracts on α-glucosidase activity and albumin glycation was investigated, and cell viability was estimated in HT-29 human colorectal cells. Phenolic and flavonoid contents and antiradical activity were also detected. The extracts were examined using HPLC-DAD analysis.

KEY FINDINGS

The methanol and dichloromethane leaf extracts showed a significant concentration-dependent inhibition of α-glucosidase activity (IC50= 3.73 and 21.28 µg/ml, respectively). Both extracts also inhibited ribose-induced glycation of bovine serum albumin from 250 µg/ml. Phytochemical analysis revealed the presence of chlorogenic acid and α-mangostin in the extracts. The extracts did not change HT-29 cell viability up to 250 µg/ml, thus showing very low cytotoxicity.

CONCLUSIONS

The methanol leaf extract of T. africana inhibited α-glucosidase activity in a concentration-dependent manner, supporting the use of the leaves in traditional medicine to control hyperglycaemia. Chlorogenic acid and α-mangostin, the latter identified for the first time in this species, were found in the T. africana leaves. Further, in vivo studies and pilot clinical trials should be conducted using standardized T. africana leaf extracts to evaluate their potential effectiveness in diabetes mellitus.

Antioxidant Characterization of Six Tomato Cultivars and Derived Products Destined for Human Consumption

The consumption of fresh tomatoes and processed tomato products is widespread in the Mediterranean diet. This fruit is a valuable source of antioxidants and plays an important role in preventing oxidative stress. This study aimed to investigate the content of antioxidants and measure the total antioxidant capacity (ABTS and DPPH assays) in the peel, pulp, and seed fractions of six tomato cultivars. Finally, some bioactive compounds and total antioxidant activity were also determined in homemade tomato purees, since such homemade production is commonplace in Southern Italy. The level of antioxidants and total antioxidant capacity in each fraction were also calculated based on their actual fresh weight in the whole tomato. The overall results indicated that the peel and seeds of all analysed tomato cultivars contribute significantly to the antioxidant charge of the fruits. Consequently, consuming tomatoes without peel and seeds results in a substantial loss of compounds beneficial for human health. Our results also showed that phenolic and lycopene content, as well as antioxidant activities in all purees are higher than in fresh tomatoes. Based on this evidence, producing homemade tomato puree is a good practice, and its consumption helps prevent oxidative stress damage.

Nanoencapsulation of thyme essential oil: a new avenue to enhance its protective role against oxidative stress and cytotoxicity of zinc oxide nanoparticles in rats

Although the green synthesis of nanometals is eco-friendly, the toxicity or safety of these biosynthesized nanoparticles in living organisms is not fully studied. This study aimed to evaluate the potential protective role of encapsulated thyme oil (ETO) against zinc oxide nanoparticles (ZnO-NPs). ETO was prepared using a mixture of whey protein isolate, maltodextrin, and gum Arabic, and ZnO-NPs were synthesized using parsley extract. Six groups of male Sprague-Dawley rats were treated orally for 21 days which included the control group, ZnO-NP-treated group (25 mg/kg body weight (b.w.)), ETO-treated groups at low or high dose (50, 100 mg/kg b.w.), and the groups that received ZnO-NPs plus ETO at the two tested doses. Blood and tissue samples were collected for different assays. The results showed that carvacrol and thymol were the major components in ETO among 13 compounds isolated by GC-MS. ZnO-NPs were nearly spherical and ETOs were round in shape with an average size of 38 and 311.8 nm, respectively. Administration of ZnO-NPs induced oxidative stress, DNA damage, biochemical, ctyogentical, and histological changes in rats. ETO at the tested doses alleviated these disturbances and showed protective effects against the hazards of ZnO-NPs. It could be concluded that encapsulation of thyme oil using whey protein isolate, maltodextrin, and gum Arabic improved the antioxidant properties of ETO, probably possess synergistic effects, and can be used as a promising tool in pharmaceutical and food applications.

Antioxidant potentials and effects on the hematology and osmotic fragility scores of a polyherbal formulation used in Southeast Nigeria

Background In this study, the hematological and antioxidant potential as well as the osmotic fragility effects of a Nigerian polyherbal formulation were evaluated. Materials and methods A total of 40 fats were divided into four groups of 10 rats each. Group 1 served as the control group, and the rest were assigned increasing daily oral administration of the extract for 28 days. At the end of treatment, blood was collected for hematological and osmotic fragility studies. The free radical scavenging effect of the extract was investigated via different in vitro models as well. Results Results showed that the nitric oxide scavenging and 2,2-diphenyl-1-picrylhydrazyl (DPPH) activities of the extract were significant (p < 0.05) and compared favorably with that of vitamin C. At 200 and 400 μg/mL, the nitric oxide scavenging activities for Ajumbise Polyherbal Extract (APE) were 60.71 ± 0.25% and 59.49 ± 0.98%, respectively, whereas for the same concentrations of vitamin C, 74.60 ± 0.25% and 85.24 ± 0.14 scavenging activities were obtained. The (DPPH) activity at 100 μg/mL was 81.24 ± 0.02% for the extract and 96.22 ± 0.18% for vitamin C. However, at all concentrations, the extract had significantly lower Ferric Reducing Antioxidant Power (FRAP) activity than vitamin C. Red blood cell counts (RBCC), hemoglobin and packed cell volume values (PCV) were significantly lowered only in groups treated with 400 and 800 mg/kg of the extract (p < 0.05), whereas other RBCC parameters and white blood cell counts (WBCC) were not significantly affected (p < 0.05). Platelet (PLT) count was also significantly lowered in all extract-treated groups. The extract also significantly reduced RBCC percentage hemolysis (p < 0.05). Conclusions Ajumbise polyherbal may be free of hematoxicity and may improve the integrity of the RBC membrane due to its appreciable antioxidant activity.