The nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway is an important cell signaling mechanism in maintaining redox homeostasis in humans. The role of dietary flavonoids in activating Nrf2/ARE in relation to cancer chemoprevention or cancer promotion is not well established. Here we summarize the dual effects of flavonoids in cancer chemoprevention and cancer promotion with respect to the regulation of the Nrf2/ARE pathway, while underlying the possible cellular mechanisms. Luteolin, apigenin, quercetin, myricetin, rutin, naringenin, epicatechin, and genistein activate the Nrf2/ARE pathway in both normal and cancer cells. The hormetic effect of flavonoids has been observed due to their antioxidant or prooxidant activity, depending on the concentrations. Reported in vitro and in vivo investigations suggest that the activation of the Nrf2/ARE pathway by either endogenous or exogenous stimuli under normal physiological conditions contributes to redox homeostasis, which may provide a mechanism for cancer chemoprevention. However, some flavonoids, such as luteolin, apigenin, myricetin, quercetin, naringenin, epicatechin, genistein, and daidzein, at low concentrations (1.5 to 20 µM) facilitate cancer cell growth and proliferation in vitro. Paradoxically, some flavonoids, including luteolin, apigenin, and chrysin, inhibit the Nrf2/ARE pathway in vitro. Therefore, even though flavonoids play a major role in cancer chemoprevention, due to their possible inducement of cancer cell growth, the effects of dietary flavonoids on cancer pathophysiology in patients or appropriate experimental animal models should be investigated systematically.

Clitoria ternatea L. commonly known as ‘blue pea’ is an underutilized plant in Sri Lanka. The blue coloured flower of this plant is used in medicine in Sri Lankan traditional medical system and also reported to have several health benefits in recent findings at the international level. However, to date scientifically validated value added products from blue pea flower (BPF) is very limited worldwide. In this connection, this study was carried out to develop a commercial potential blue pea flower extract (BFE) incorporated beverage having functional properties. Dried BPFs were extracted into water with varying flower: water ratio, temperature, and time using response surface methodology (RSM) along with Box–Behnken design. A range of BFE incorporated beverages was developed comprising a natural sweetener (Stevia extract) and a flavour (lime). The most acceptable formulation was selected via ranking and hedonic sensory tests. Further, it was evaluated for functional properties in terms of antioxidant activity via total polyphenolic and flavonoid contents, ferric reducing antioxidant power and radical scavenging activities via ORAC; DPPH and ABTS. Glycaemic regulatory properties (GCP) were evaluated in terms of antiamylase and antiglucosidase activities. Quality parameters of the developed beverage were evaluated for a period of 28 days at different time intervals and a colour chart was also developed. The optimum conditions for extraction of BPF via RSM were 3 g of powdered BPF/L of water at 59.6 °C for 37 min. The most acceptable formulation consists of BFE, Stevia extract, and lime at a ratio of 983.25:1.75:15. Further, it had significantly higher (p<0.05) consumer preference for sensory attributes. Further, it possesses an antioxidant activity through multiple mechanisms while GCP were not detected. Moreover, it was shelf stable for a period of 28 days without preservatives. The colour chart can be used to monitor the quality of the beverage.

Cancer is one of the leading causes of death worldwide. Chemotherapy and radiation therapy are currently providing the basis for cancer therapies, although both are associated with significant side effects. Thus, cancer prevention through dietary modifications has been receiving growing interest. The potential of selected flavonoids in reducing carcinogen-induced reactive oxygen species (ROS) and DNA damage through the activation of nuclear factor erythroid 2 p45 (NF-E2)-related factor (Nrf2)/antioxidant response element (ARE) pathway was studied in vitro. Dose-dependent effects of pre-incubated flavonoids on pro-carcinogen 4-[(acetoxymethyl)nitrosamino]-1-(3-pyridyl)-1-butanone (NNKAc)-induced ROS and DNA damage in human bronchial epithelial cells were studied in comparison to non-flavonoids. The most effective flavonoids were assessed for the activation of Nrf2/ARE pathway. Genistein, procyanidin B2 (PCB2), and quercetin significantly suppressed the NNKAc-induced ROS and DNA damage. Quercetin significantly upregulated the phosphorylated protein kinase B/Akt. PCB2 significantly upregulated the activation of Nrf2 and Akt through phosphorylation. Genistein and PCB2 significantly upregulated the phospho-Nrf2 nuclear translocation and catalase activity. In summary, genistein and PCB2 reduced the NNKAc-induced ROS and DNA damage through the activation of Nrf2. Further studies are required to understand the role of dietary flavonoids on the regulation of the Nrf2/ARE pathway in relation to carcinogenesis.

Butterfly pea (Clitoria ternatea L.) is used for production of herbal teas, herbal juices and having a potential to use in culinary purposes. Even though, it is grown widely in Sri Lanka, comprehensive information and studies conducted on three popular varieties are still lacking. Hence, the aim of this study was to evaluate the elemental compositions, phytochemical properties of three C. ternatea L. flower varieties grown in Sri Lanka; white flower with normal keel petals (WSPF), blue flower with normal keel petals (BSPF), and blue flower with enlarged keel petals (BMPF). Total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power (FRAP) and DPPH radical scavenging activity in aqueous extracts of C. ternatea flowers were determined using spectrophotometric methods. Kjeldahl method was used to determine the nitrogen content and crude protein % was calculated by multiplying the nitrogen content by a standard factor. Phosphorus content (UV spectrophotometer) and calcium and potassium contents (flame photometer) of the flower samples were measured by using a general mineralization procedure.The maximum TPC and highest level of TFC were reported in BMPF (31.88 mg GAE eq./g dry weight and 15.96 mg quercetin eq./g dry weight of flower) whereas FRAP of WSPF was significantly lower (10.66 mg trol eq./g dry weight of flower). FRAP of BSPF (14.56 mg trol eq./g dry weight of flower) and BMPF (18.50 mg trol eq./g dry weight of flower) were not significantly statistically different. BSPF showed significantly highest level of DPPH radical scavenging activity that was 11.97 mg trol. eq./g dry weight of flower. Meanwhile, the DPPH radical scavenging activity of BMPF and WSPF were not significantly different to each other. Mean P content was highest in WSPF and was lowest in BMPF (4.65 and 4.19 mg/g respectively). The N content was significantly higher (p<0.05) in both BSPF and WSPF (43.12 mg/g and 42.35 mg/g respectively). Significantly higher (p<0.05) mean protein contents were detected for BSPF and it was 26.95%. This is the first such detailed report on chemical composition and antioxidant properties of three main C. ternatea flower varieties grown in Sri Lanka.

Macro and micro elemental nutrient profiles and compositions of toxic heavy metals in food items are important attributes in culinary and nutrition sciences. We selected ripen bael fruits of elite accessions selected for large-scale cultivation in Sri Lanka, Kankong, a green leafy vegetable prone to bioaccumulation of toxic heavy metals (market and commercially available samples) and shoot-tops of sweet potato, an underutilized leafy vegetable to detect the elemental compositions using X-ray fluorescence (XRF) and Inductive Coupled Plasma Mass Spectrometric (ICP-MS) methods. Bael pulp was extracted from ripe fruits and, Kankong and sweet potato shoot-tops were collected. The presence and absence of elements were assessed using XRF. The elemental contents were measured using ICP-MS, and statistically analyzed. Bael and SP samples did not contain toxic heavy metals As and Pb whereas Kankong samples collected from a municipal wastewater drain contained all these toxic elements in large quantities. Kankong samples purchased from open market contained Hg, Cd, As and Cr. It is also noted that Pb separately correlated with Cr, Fe, Co, Zn, Ni and Hg contents in Kankong implying that they are under a common absorption mechanism or coming from a common source in the polluted habitat. The present study concludes that Kankong in Sri Lanka is unsafe for consumption and SP is an alternative to replace Kankong.