A new anti-hypoxia sesquiterpene from the rhizome of Petasites japonicas.

A new sesquiterpene, bakkenolide-Ⅵa (1), was isolated from the rhizome of Petasites japonicas (Sieb. et Zucc.) Maxim. The structure was characterized on the basis of various NMR ((1)H, (13)C, (1)H-(1)H COSY, HMQC, HMBC and NOESY) and mass spectrometry data. Bakkenolide-Ⅵa showed potent cerebral hypoxia- ischemia protective activity in mice subjected to decapitation through prolonging the survival time and gasping time. It also exhibited a protective activity against hypoxia injury in PC12 cells in anaerobic culture by inhibition of lactate dehydrogenase (LDH) release.

Effect of repeated retrogradation on structural characteristics and in vitro digestibility of waxy potato starch.

The effects of repeated retrogradation (RR) treatment on the structural characteristics and in vitro digestibility of waxy potato starch were investigated. The cycling times of RR ranging from 1 to 5 were designated as RR-1, RR-2, RR-3, RR-4, and RR-5, respectively. A maximum SDS content (40.41%) was obtained by RR-2 treatment with the time interval of 48h. RR-2-treated starch product exhibited a narrower melting temperature range, a higher onset temperature and a lower melting enthalpy compared with RR-1 treatment. Compared with native starch, X-ray diffraction patterns of treated starches were altered from B-type to C-type. The variation in relative crystallinity of RR-treated starch products was consistent with that in melting enthalpy. Moreover, compared with RR-1-treated starch, a large number of cavities were observed on the surface of RR-2-treated starch product with a time interval of 48h, whereas more smooth regions were found on the surface of RR-5-treated starch product. This study suggested that structural changes of waxy potato starch treated with different cycling times of RR significantly affected the digestibility.

Effect of single-, dual-, and triple-retrogradation treatments on in vitro digestibility and structural characteristics of waxy wheat starch.

The effects of single-retrogradation (SR), dual-retrogradation (DR) and triple-retrogradation (TR) treatments on in vitro digestibility and structural characteristics of waxy wheat starch were investigated. The yield of slowly digestible starch in a DR-treated starch with retrogradation time interval of 48 h reached a maximum of 44.41%. The gelatinization temperature range and gelatinization enthalpy of DR-treated starch samples were the lowest. Moreover, compared with native starch, X-ray diffraction patterns of treated starches were altered from A-type to B-type and relative crystallinity was significantly decreased, which was responsible for the interaction between amylose-amylose and/or amylose-amylopectin chains that may generate more imperfect structures. Scanning electron micrographs revealed that compared with SR-treated and TR-treated starches, the surface of DR-treated starch with a retrogradation time interval of 48 h exhibited a net-like structure with numerous cavities. These results suggest that structural changes of waxy wheat starch by cycled retrogradation treatment significantly affect digestibility, and DR treatment can be used for preparing SDS product.

Effect of temperature-cycled retrogradation on in vitro digestibility and structural characteristics of waxy potato starch.

The effects of temperature-cycled retrogradation treatment on the structural characteristics and in vitro digestibility of waxy potato starch were investigated in this study. The results showed that the maximum yield of slowly digestible starch (SDS) in waxy potato starch reached 38.63% by retrogradation treatment under temperature cycles of 4/25°C for 3 days with an interval of 24h. The starch products prepared under the temperature cycles of 4/25°C exhibited a narrower melting temperature range (Tc-To), a higher melting enthalpy (ΔH) and a higher IR absorbance ratio (1047cm(-1)/1022cm(-1)) than that prepared at a constant temperature of 25°C. Compared to native starch, X-ray diffraction pattern of treated starch was altered from B-type to C-type. Furthermore, the relative crystallinity of the starch products prepared under temperature-cycled retrogradation was the highest. This study suggests that more imperfect crystallites are formed in the crystalline matrix under temperature-cycled retrogradation, resulting in a high yield of SDS.