11Purple-fleshed sweet potato P40 has been shown to prevent colorectal cancer in a murine 12 model. This study is to identify anthocyanins by using HPLC/MS-MS and assess the stability 13 during various cooking conditions. P40 possesses a high content of anthocyanins up to 14 mg/g 14 dry matter. Total 12 acylated anthocyanins are identified. Top three anthocyanins, e.g., cyanidin 15 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside, peonidin 3-caffeoyl sophoroside-5-16 glucoside, and cyanidin 3-(6'' -caffeoyl-6''-feruloylsophoroside)-5-glucoside, account for half 17 of the anthocyanin contents. Over 80% of anthocyanins measured by acid hydrolysis were 18 cyanidin derivatives, indicating P40 is unique when compared with other purple-fleshed sweet 19 potatoes that usually contain more peonidin than cyanidin. Steaming, pressure cooking, 20 microwaving, and frying but not baking significantly reduced 8-16% of total anthocyanin 21 contents. Mono-acylated anthocyanins showed a higher resistance against heat than di-and non-22 acylated. Among of which, cyanidin 3-p-hydroxybenzoylsophoroside-5-glucoside exhibited the 23 best thermal stability. The stable acylated and cyanidin-predominated anthocyanins in P40 may 24 provide extra benefits for cancer prevention. 25Keywords: Anthocyanins / purple-fleshed sweet potato / cancer prevention / stability / cooking 26 conditions 27
Scope
Anthocyanins, the natural pigments in plant foods, have been associated with cancer prevention. However, the content of anthocyanins in staple foods is typically low and the mechanisms by which they exert anti-cancer activity is not yet fully defined.
Methods and results
We selected an anthocyanin-enriched purple-fleshed sweet potato clone, P40, and investigated its potential anti-cancer effect in both in vitro cell culture and in vivo animal model. In addition to a high level of total phenolics and antioxidant capacity, P40 possesses a high content of anthocyanins at 7.5 mg/g dry matter. Treatment of human colonic SW480 cancer cells with P40 anthocyanin extracts at 0–40 μM of peonidin-3-glucoside equivalent resulted in a dose-dependent decrease in cell number due to cytostatic arrest of cell cycle at G1 phase but not cytotoxicity. Furthermore, dietary P40 at 10–30% significantly suppressed azoxymethane-induced formation of aberrant crypt foci in the colons of CF-1 mice in conjunction with, at least in part, a lesser proliferative PCNA and a greater apoptotic caspase-3 expression in the colon mucosal epithelial cells.
Conclusion
These observations, coupled with both in vitro and in vivo studies reported here, suggest anthocyanin-enriched sweet potato P40 may protect against colorectal cancer by inducing cell cycle arrest, anti-proliferative and apoptotic mechanisms.
Net photosynthesis (Pn) of two ecotypes of redbud (Cercis canadensis L.) was studied following growth under high temperatures and increasing drought. Although mexican redbud [C. canadensis var. mexicana (Rose) M. Hopkins] exhibited greater Pn than eastern redbud (C. canadensis var. canadensis L.), Pn decreased at a similar rate under water deficit stress for both ecotypes. Mexican redbud also had greater instantaneous water use efficiency [net photosynthesis: transpiration (WUE)] than eastern redbud. Differences in both Pn and WUE might have been due to differences in leaf thickness. The optimum temperature for potential photosynthetic capacity (37 °C) was unaffected by irrigation or ecotype. Tissue osmotic potential at full turgor was more negative in eastern redbud, but was unaffected by drought stress in either ecotype. Soluble carbohydrate content was higher in eastern redbud, and in both ecotypes, d-pinitol was the major soluble carbohydrate and was considerably more abundant in the water-stressed plants. Total polyol content (myo-inositol + ononitol + pinitol) was also greater in the water-stressed plants. Both ecotypes were very tolerant of high temperatures and drought.
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