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.

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Starch can be derivatized with various functional groups to achieve different physicochemical properties. For decades, researchers have focused on lightly substituted starches since these starches can be prepared economically in aqueous slurries. In contrast, modified starches having high or intermediate degree of substitution have not been thoroughly investigated or extensively used, mainly because their conventional preparation involves harmful solvents that renders their purification uneconomical. Aiming to explore possible industrially feasible routes for producing medium and highly substituted starch derivatives, this review summarizes developments in synthetic methods, especially the influence of synthesis media and reaction conditions. In addition, crucial physicochemical properties of those highly substituted starches are discussed.