Histological studies on the relationship between the low seed set and abnormal embryo sacs in sweet potato, Ipomoea batatas (L.) Lam.

This study aimed to investigate the relationship between low seed set and abnormal embryo sacs lacking normal female organs, such as one egg cell, two assistant cells, and two polar nuclei, in Ipomoea trifida, which is closely related to sweet potato, and sweet potato cultivars and lines, through histological analysis of their ovaries on flowering day. Ovaries of diploid, tetraploid, and hexaploid lines of I. trifida each had four ovules, except for some hexaploid lines with five or six ovules. Almost all sweet potato cultivars and lines had four ovules per ovary, although some sib-cross lines had two or three ovules. The number of ovules per ovary did not have direct effects on low seed set. The frequency of abnormal embryo sac increased with polyploidy in I. trifida. However, it varied among different sweet potato cultivars and lines. Moreover, the variation in abnormal embryo sacs occurred at an earlier stage of gametogenesis (type A) in the tetraploid and hexaploid plants of I. trifida and sweet potato cultivars and lines. These findings suggest that the high frequency of abnormal embryo sacs is a primary cause of low seed set in sweet potato and that it is closely related to the decline in seed propagation that occurs in the evolution process of sweet potato.

Increased phenolic content and antioxidant capacity of the heated leaves of yacon (Smallanthus sonchifolius).

We investigated the content of phenolic compounds and antioxidant capacity of two batches of non-heated and heated leaves of the yacon cultivar "Andes no yuki", grown in Japan. Lyophilized yacon leaves heated at 160°C for 20 min and 100°C for 60 min had a 1.96 to 9.69-times higher total phenolic content than that of the non-heated leaves. Heated leaves exhibited a 1.98 to 4.07-times higher antioxidant capacity than that of the non-heated leaves in three different free radical scavenging assays. Heated leaves were more efficient at attenuating the superoxide anion radical production in human granulocytic cells than the non-heated leaves. High-performance liquid chromatography analysis revealed that, in the heated leaves, the caffeic acid content was 2.13 to 3.64-times higher and the chlorogenic acid content was slightly lower than those in the non-heated leaves. Hence, heat processing may affect the active constituent contents in yacon leaves, potentiating its antioxidant capacity.Abbreviations: ABTS+: 2,2'-azinobis(2-ethylbenzothiazoline-6-sulfonic acid) cation; DPPH: 1,1-diphenyl-2-picrylhydrazyl, HPLC: high-performance liquid chromatography; NBT: nitroblue tetrazolium; O2-: superoxide anion; PMA: phorbol 12-myristate 13-acetate; PMS: phenazine methosulfate; TEAC: Trolox equivalent antioxidant capacity.

Antioxidant Effects of Herbal Tea Leaves from Yacon (Smallanthus sonchifolius) on Multiple Free Radical and Reducing Power Assays, Especially on Different Superoxide Anion Radical Generation Systems.

UNLABELLED: Yacon (Smallanthus sonchifolius), a native Andean plant, has been cultivated as a crop and locally used as a traditional folk medicine for the people suffering from diabetes and digestive/renal disorders. However, the medicinal properties of this plant and its processed foods have not been completely established. This study investigates the potent antioxidative effects of herbal tea leaves from yacon in different free radical models and a ferric reducing model. A hot-water extract exhibited the highest yield of total polyphenol and scavenging effect on 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical among four extracts prepared with hot water, methanol, ethanol, and ethylacetate. In addition, a higher reducing power of the hot-water extract was similarly demonstrated among these extracts. Varying concentrations of the hot-water extract resulted in different scavenging activities in four synthetic free radical models: DPPH radical (EC50 28.1 µg/mL), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical (EC50 23.7 µg/mL), galvinoxyl radical (EC50 3.06 µg/mL), and chlorpromazine cation radical (EC50 475 µg/mL). The yacon tea-leaf extract further demonstrated superoxide anion (O2(-)) radical scavenging effects in the phenazine methosulfate-NADH-nitroblue tetrazolium (EC50 64.5 µg/mL) and xanthine oxidase assay systems (EC50 20.7 µg/mL). Subsequently, incubating human neutrophilic cells in the presence of the tea-leaf extract could suppress the cellular O2(-) radical generation (IC50 65.7 µg/mL) in a phorbol 12-myristate 13-acetate-activated cell model. These results support yacon tea leaves may be a good source of natural antioxidants for preventing O2(-) radical-mediated disorders. PRACTICAL APPLICATION: Yacon has been considered to be a potent alternative food source for patients who require a dietary cure in regional area, while the leaf part has been provided and consumed as an herbal tea in local markets. We demonstrated here potent antioxidative effects of the tea leaves from yacon in different free radical assays, reducing power assay, and cellular superoxide anion radical generation assay. Results support yacon tea leaves may be a good source of natural antioxidants for preventing O2(-) radical-mediated disorders.