Oolong tea, partially fermented from Camellia sinensis leaves, exhibits significant antioxidative, anti-inflammatory, and anti-cancer activities as indicated in several in vitro and in vivo studies. However, studies on health promoting effects of oolong tea and its characteristic compounds are limited. The potential efficacy of bioactives derived from oolong tea and their roles as promising anticancer agents, their cardio-protective benefits during hypoxic conditions, effects in treating allergic disorders, potential prebiotic activities, improvement of blood lipid status in human beings, effectivity as oral hypoglycemic agent in the treatment of type 2 diabetes, and their potentials to reduce the risk of obesity have been discussed in this review. These promising studies mainly gained from animal studies might broaden the consumption and usage of the phenolic-enriched oolong tea and its products in food and pharmaceutical industries. However, potential health beneficial effects of oolong tea in humans should be further complemented by large-sized, randomized double-blind and placebo-controlled trials to consolidate potential therapeutic applications.

Effects of an enriched orange peel extract (OPE) against type 2 diabetes (T2D) were analyzed in ZDF rats which were hyperglycemic, dyslipidemic and express pro-inflammatory markers. Glucose related parameters were lowered in the lean control and metformin group as compared to ZDF vehicle controls. OPE was well tolerated and induced a decline in fasted blood glucose and increase levels of fed glucose although to a lesser degree as compared to metformin. However, OPE did not improve glucose tolerance but showed significantly elevated glucose levels. Furthermore, OPE treatment caused an increase of free fatty acids in a dose-responsive manner as well as elevated levels of cholesterol and LDL. The analysis of inflammatory mediators revealed a significant down-regulation of COX-2, ICAM-1, and TNF-α in epididymal adipose tissue in response to OPE to a higher degree as compared to ibuprofen. In whole blood, IL-4 was upregulated in a dose-responsive manner as measured by ELISA. In summary, lipophilic OPE showed strong anti-inflammatory effects in adipose tissue, ambivalent effects against hyperglycemia, whereas hyperlipidemia was increased. Our study emphasize the complexity of anti-diabetic regimen suggesting a treatment with OPE to reduce inflammation in adipose tissue in combination with antidiabetic therapeutics as promising strategy against T2D.

The interest in food toxicology is evident by the dependency of humankind on nutrition by virtue of their heterotrophic metabolism. By means of modern biochemistry, molecular and cell biology, computer science, bioinformatics as well as high-throughput and high-content screening technologies it has been possible to identify adverse effects and characterize potential toxicants in food. The mechanisms of toxicant actions are multifactorial but many toxic effects converge on the generation of oxidative stress and chronic inflammation resulting in cell death, aging and degenerative diseases. Integration of food toxicology data obtained throughout biochemical and cell-based in vitro, animal in vivo and human clinical settings has enabled the establishment of alternative, highly predictable in silico models. These systems utilize a combination of complex in vitro cell-based models with computer-based algorithms. A decrease of rodent animal testing with its limitations of high costs, low throughput readouts, inconsistent responses, ethical issues and concerns of extrapolability to humans have led to an increased use of these but also alternative lower hierarchy surrogate animal models (e.g. Drosophila melanogaster; Caenorhabditis elegans or Danio rerio) and efforts to integrate organotypic systems and stem cell-based assays. Despite those achievements, there are numerous challenges in various disciplines of food toxicology.

In view of the potential of polymethoxyflavones (PMFs) and hydroxylated PMFs (OH-PMFs) as bioactives against inflammation, we prepared six different orange peel extracts (OPEs). The major compounds of these extracts were characterized and quantified by high performance liquid chromatography (HPLC). Effects on inflammation were analyzed by nutrigenomics using a human cell-based TPA-induced monocyte–macrophage differentiation model employing U-937 cells and inflammatory surrogate genes. Dose response and kinetics analysis of OPEs with different chemical profiles revealed less cytotoxic effects of PMFs as compared to OH-PMFs as demonstrated by the MTT-method. Noteworthy, a comparison of two PMF members such as 3,5,6,7,3′,4′-hexamethoxyflavone (HexaMF) and 3,5,6,7,8,3′,4′-heptamethoxyflavone (HeptaMF) exhibited less cytotoxic effects of HeptaMF as compared to HexaMF. A specific OPE enriched with HeptaMF, PMFs and OH-PMFs at low concentrations (10 μg/mL) significantly down-regulated the expression of a panel of genes involved in inflammatory response, including COX-2, TNF-α, ICAM-1, NFκB, IL-1β, IL-6, and IL-8 with an inflammatory index of −0.55. The strong anti-inflammatory effects were then validated in a mouse carrageenan-induced paw edema model. Oral intake of OPE reduced paw edema significantly in a dose-dependent manner. Importantly, a dosage of 250 mg/kg gave an anti-inflammatory effect comparable to ibuprofen. A preliminary clinical study showed that OPE was well tolerated showing no adverse side effects. In summary, enrichment of phyto extracts such as OPEs with specific polymethoxyflavones as anti-inflammatory bioactives is a promising strategy to find naturally derived extracts that are effective against diseases associated with inflammation.