Antioxidants are understood to play a key role in disease prevention; because of this, research and interest in these compounds are ever increasing. Antioxidative phytochemicals from natural sources are preferred, as some negative implications have been associated with synthetic antioxidants. Beans, nuts, seeds, fruits, and vegetables, to name a few, are important sources of phytochemicals, which have purported health benefits. The aforementioned plant sources are reportedly rich in bioactive compounds, most of which undergo some form of processing (boiling, steaming, soaking) prior to consumption. This article briefly reviews selected plants (beans, nuts, seeds, fruits, and vegetables) and the effects of processing on the antioxidant potential, availability, and bioavailability of phytochemicals, with research from our laboratory and other studies determining the health benefits of and processing effects on bioactive compounds. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 12 is March 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Colon cancer is the third leading cause of death in the US. Herbal teas and spices may reduce the incidence of chronic diseases, including colon cancer. The objectives of this study were to determine the chemopreventive effects of herbal teas and cinnamon in an in-vitro cell model and to evaluate the inhibitory effects of selected extracts on enzymes associated with inflammatory disease. Effects of raspberry leaf (0.5-2.0 mg/mL), strawberry leaf (0.4-1.0 mg/mL), hibiscus flower (4.0-10.0 mg/mL) and cinnamon (400-1500 μg/mL) were evaluated for cytotoxicity, induction of caspase and DNA fragmentation in colon cancer (Caco-2) cells to determine possible chemopreventive effects. Effects of extracts on inhibition of cyclooxygenase-2 (COX-2) were also measured to determine possible anti-inflammatory potential. Caco-2 cells were obtained from American Type Culture Collection (ATCC) and maintained in Dulbecco's Modified Eagle's Medium with 10% fetal bovine serum. As concentrations of tea increased, LDH release from Caco-2 cells increased, with cytotoxicity ranging from 1%-80% (hibiscus flower 1.0 mg/mL and strawberry leaf (1.0 mg/mL) for teas. All extract concentrations of herbal teas and cinnamon were able to enhance caspase-3 activity with lowest activity (4.4 mmol/ min/mL) observed in the lowest concentration of cinnamon (400 μg/mL) and highest activity (6.0 mmol/min/mL) seen in the highest concentration of raspberry leaf (2 mg/mL). Tea and spice extracts were able to induce apoptosis in Caco-2 cells exhibited by increased DNA fragmentation (expressed as enrichment factor). Enrichment factor ranged from 1.0-1.5 (raspberry leaf 1.0 mg/mL and hibiscus 10.0 mg/mL). Teas and cinnamon exhibited anti-inflammatory potential by inhibiting COX-2 by 0.6%-8.0% (raspberry leaf 1.0 mg/mL and strawberry leaf 0.8 mg/mL). The results suggest that herbal teas and cinnamon may have significant benefits in chemoprevention.
Tiger nut (Cyperus esculentus), commonly referred to as chufa, is a "nut-like" tuber, native to tropical and Mediterranean regions. It is often consumed in the form of a beverage (horchata de chufa). Health benefits of tiger nut have been attributed to presence of phytochemicals and their antioxidant potential. Tiger nut is often processed in order to enhance sensory characteristics. The objective of study was to determine effects of processing on antioxidant content, potential and inhibition of metabolizing enzyme activities of tiger nuts. Total phenolic content (TPC), total flavonoid content (TFC), free radical scavenging activity by 1,1-diphenyl-2-picryhydrazyl (DPPH), trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) and inhibition of lipase and α-amylase were evaluated in raw tiger nuts extracted with water (TRWA) and methanol (TRWM) and roasted (110˚C -115˚C for 10 mins) tiger nuts extracted with water (TRA) and methanol (TRM). Highest phenolic content was observed in TRWA (1186.68 GAE/100g) and TRWM had lowest (43.77 GAE/100g). TRWA also exhibited highest ferric reducing ability with a FRAP value of 169.83 mm Fe 2+ /100g). TRWM had a higher flavonoid content (220.68 CAE/100g) compared to all other extracts. At a concentration of 0.02 mg/ml, all extracts reached at least 50% inhibition of DPPH, while highest scavenging activity was observed in TRM (58%). Highest TEAC was observed in TRM with 55.66% of ABTS radical scavenged. TRA had a significantly higher ability to inhibit α-amylase and lipase compared to other extracts. Results suggest that processing had an effect on the antioxidant potential of tiger nut, and this tuber may benefit consumers by improving their antioxidant status.
Colored potatoes are an interesting alternative to the traditional, white-creamed potatoes, due to their high phytochemical content, which have been proved to have antioxidative properties. The extraction of polyphenols is highly dependent on using the appropriate solvent systems. Therefore, polyphenol extraction in colored potatoes [Vermillion Fingerling (VF); Jester Potato (JP); Magic Molly (MM); Blue Belle (BB); All Blue (AB)] using different solvents [Solvent A (24% water, 67% ethanol 9% acetic acid); Solvent B (5% acetic acid); and Solvent C (95% water, 5% acetic acid, 0.5 g sodium bisulfate)] may have significant effects on extraction efficiency and phytochemical content. Total phenolic content (TPC), Total flavonoid content (TFC), Total anthocyanin content (TAC) and antioxidant activities [Trolox Equivalent Antioxidant Capacity (TEAC) and Ferric reducing-antioxidant power (FRAP)] were determined. Solvent A extracted significantly (p < 0.05) higher TPC from BB (13.93 mg GAE/100g) compared to the other solvents. VF and JP displayed higher TFC (14.53 and 19.46 mg CE/100g, respectively) when Solvent C was utilized. VF and JP extracts with Solvent C displayed the highest FRAP value compared to Solvent B. MM displayed the highest TAC using Solvent A and C. Potato variety resulted in high variability in polyphenols content and antioxidant activity. The utilization of colored potatoes or extracts in the food industry could provide innovative products and a functional alternative to the traditional.
Spices (turmeric (T), ginger (GI), and garlic (GA) (TGG)) have been used for centuries for food preservation, flavors, and medicinal properties. Research suggests that TGG contain potent antioxidants that may prevent and/or delay chronic diseases such as cancer, diabetes, and heart diseases. Heat treatment of spices may potentially increase antioxidative activity by modifying the inherent chemical structure of potent antioxidative compounds in spices. The purpose of this study was to determine the anti-diabetic potential of thermally treated TGG on Wistar male rats. Two-week-old male Wistar rats were randomly assigned to 8 groups (N = 24, n = 3) including control AIN-93G Diet (C) and high fat (HFD) and high sugar (HS) (glucose 10%) diet and treatment HFD/HS diets containing T, GA, GI (1% and 2%) singly for 11 weeks. Weekly feed intake, body weight, and blood glucose levels were recorded. Rats were sacrificed at 13 wks. by CO 2 asphyxiation. Liver, pancreas, adipose (thigh), cecum, femur, urine, and serum samples were collected for quantitative determination of detoxification and antioxidative enzyme analysis, bone mineralization, and cholesterol using standard protocol. Of spice-incorporated diets, rats fed turmeric (1%) exhibited the lowest reduction in blood glucose levels at 90 mg/dL compared to the control 58 mg/dL. Additionally rats fed TGG at both concentrations resulted in an induction of antioxidant (GSH) and antioxidant enzyme (GPx) activity with significantly (p ≤ 0.05) higher levels compared to the control. Serum total cholesterol levels were lower in spice-incorporated diets compared to control HFD/HS fed rats. Therefore, the use of thermal application on spices presents promise in potentiating the antioxidant effects and thereby their potential health promoting properties.
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