Purple yam (Dioscorea alata L.), which is widely distributed in tropical and subtropical regions, is characterized by its color and viscosity. Previous studies have shown that purple yams contain a variety of acylated anthocyanins that exhibit higher levels of antioxidant activity than the corresponding nonacylated compounds. In this study, the pigments found in purple yams from the Philippines (D. alata) were isolated and evaluated in terms of antioxidant activity. Four new acylated anthocyanins, alanins (1–4) were isolated from the MeOH extracts of purple yam, which were subsequently determined to be cyanidin (1, 2, and 4) and peonidin (3) type compounds, along with four known anthocyanins (5–8). The structures of 1–4 were determined by spectroscopic methods, including NMR and MS analyses. The antioxidant activities of anthocyanins 1–8 were investigated using oxygen radical absorbing capacity and ferric reducing antioxidant power assays.

A detailed analysis of the antioxidative activity of 12 carbohydrates including chondroitin sulfate, fucoidan, agaro-oligosaccharide, 2-deoxy-scyllo-inosose (DOI), Galbeta1-4DOI, D-glucuronic acid, chitobiose, D-mannosamine, D-galactosamine, D-glucosamine, heparin, and colominic acid was performed using four established methods: 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, ferric reducing antioxidant power (FRAP) assay, superoxide dismutase (SOD) activity assay, and the deoxyribose method. Ascorbic acid and/or catechin were used as positive standards. In the DPPH radical scavenging activity measurements, fucoidan, DOI, and Galbeta1-4DOI showed remarkable levels of activity, although at lower levels than ascorbic acid. The SOD assay revealed that DOI, Galbeta1-4DOI, and agaro-oligosaccharide had high antioxidant activity, with DOI and Galbeta1-4DOI notably showing almost half of the antioxidative potency of ascorbic acid. Using the deoxyribose method, chitobiose and heparin showed the highest hydroxyl radical scavenging activity, followed by chondroitin sulfate, colominic acid, Galbeta1-4DOI, and d-glucosamine. Given that 11 of the carbohydrates analyzed share a common structure, agaro-oligosaccharide being the exception, we propose from our current results that at least one amino, carboxyl, carbonyl, or sulfonyl group is required, but is not in itself sufficient, for carbohydrates to function as antioxidants.

We measured anthocyanin levels in fresh açai (Euterpe oleracea Mart.), a native Amazonian palm fruit; cyanidin-3-O-glucoside (C3G) and cyanidin-3-O-rutinoside (C3R) in mesocarp/epicarp portion were 5.49 and 13.0 mg/g extracts, respectively, and these amounts were remarkably higher than that in endocarp. Hydrophilic ORAC assay suggested that açai mesocarp/epicarp extracts had potent antioxidant activity compared to blueberry extract. Following, absorption and excretion of açai anthocyanins were evaluated. After oral administration of açai extracts (400 mg/kg body weight) to rats, C3G and C3R appeared as intact forms in the plasma as maximum amounts of 101.0 ± 55.6 nmol/L at 60 min and 537.0 ± 99.1 nmol/L at 120 min after administration, respectively. Most of these anthocyanins were excreted in urine by 2 h post-administration time. In conclusion, fresh açai contained hydrophilic antioxidants including C3G and C3R, and therefore has strong antioxidant potency especially in the mesocarp/epicarp portion. Upon consumption, açai anthocyanins appeared as intact forms in plasma.Keywords: açai, anthocyanin, antioxidant activity, ORAC *To whom correspondence should be addressed. E-mail: kumazawa@u-shizuoka-ken.ac.jp † These authors contributed equally to this work IntroductionAnthocyanidins are important plant pigments responsible for red, blue and purple colors. Generally, anthocyanidins widely exist as glycoside derivatives, so-called anthocyanins, in colored fruits and vegetables, such as berries (Sakakibara, et al., 2003;Maatta-Riihinen, et al., 2004;Wu, et al., 2006;Koponen, et al., 2007;Ogawa, et al., 2008). Anthocyanidins and anthocyanins have been shown to exhibit a range of biological effects, including antioxidant activity, anticarcinogenesis, induction of apoptosis, anti-obesity, antidiabetes, and prevention of DNA damage (Rice-Evans, et al., 1996;Sakakibara, et al., 2002;Hou, 2003;Katsube, et al., 2003;Tsuda, et al., 2003;Cooke, et al., 2006;Duthie, 2007;Sasaki, et al., 2007;Tsuda, 2008). Interestingly, recent research suggests that anthocyanins can also prevent oxidative stress resulting from psychological stress (Rahman, et al., 2008). Consequently, the regular consumption of foods rich in anthocyanins has been considered to be associated with a reduced risk of developing chronic diseases (Harborne and Williams, 2000;Zafra-Stone, et al., 2007).Açai (Euterpe oleracea Mart.) is a palm plant widely distributed in the Amazonian area, especially Brazil. Açai is a multi-stemmed plant as shown in Fig. 1A, and its fruit looks similar to blueberry in appearance. The size of an individual açai fruit is about 1 to 1.5 cm in diameter. An outer, edible layer composed of mesocarp and very thin epicarp covers a lone, fibrous seed, consisting of the endocarp and endosperm (Fig. 1B). A ripened açai appears dark purple in color due to high amounts of anthocyanins, predominantly cyanidin-3-Oglucoside (C3G) and cyanidin-3-O-rutinoside (C3R) (Fig. 2) (Gallori, et al., 2004), indicating that açai might be one anthocyanin-rich foo...